Author name code: mueller-edith ADS astronomy entries on 2022-09-14 author:"Mueller, Edith A." ------------------------------------------------------------------------ Title: Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument Authors: Abareshi, B.; Aguilar, J.; Ahlen, S.; Alam, Shadab; Alexander, David M.; Alfarsy, R.; Allen, L.; Allende Prieto, C.; Alves, O.; Ameel, J.; Armengaud, E.; Asorey, J.; Aviles, Alejandro; Bailey, S.; Balaguera-Antolínez, A.; Ballester, O.; Baltay, C.; Bault, A.; Beltran, S. F.; Benavides, B.; BenZvi, S.; Berti, A.; Besuner, R.; Beutler, Florian; Bianchi, D.; Blake, C.; Blanc, P.; Blum, R.; Bolton, A.; Bose, S.; Bramall, D.; Brieden, S.; Brodzeller, A.; Brooks, D.; Brownewell, C.; Buckley-Geer, E.; Cahn, R. N.; Cai, Z.; Canning, R.; Carnero Rosell, A.; Carton, P.; Casas, R.; Castander, F. J.; Cervantes-Cota, J. L.; Chabanier, S.; Chaussidon, E.; Chuang, C.; Circosta, C.; Cole, S.; Cooper, A. P.; da Costa, L.; Cousinou, M. -C.; Cuceu, A.; Davis, T. M.; Dawson, K.; de la Cruz-Noriega, R.; de la Macorra, A.; de Mattia, A.; Della Costa, J.; Demmer, P.; Derwent, M.; Dey, A.; Dey, B.; Dhungana, G.; Ding, Z.; Dobson, C.; Doel, P.; Donald-McCann, J.; Donaldson, J.; Douglass, K.; Duan, Y.; Dunlop, P.; Edelstein, J.; Eftekharzadeh, S.; Eisenstein, D. J.; Enriquez-Vargas, M.; Escoffier, S.; Evatt, M.; Fagrelius, P.; Fan, X.; Fanning, K.; Fawcett, V. A.; Ferraro, S.; Ereza, J.; Flaugher, B.; Font-Ribera, A.; Forero-Romero, J. E.; Frenk, C. S.; Fromenteau, S.; Gänsicke, B. T.; Garcia-Quintero, C.; Garrison, L.; Gaztañaga, E.; Gerardi, F.; Gil-Marín, H.; Gontcho, S. Gontcho A; Gonzalez-Morales, Alma X.; Gonzalez-de-Rivera, G.; Gonzalez-Perez, V.; Gordon, C.; Graur, O.; Green, D.; Grove, C.; Gruen, D.; Gutierrez, G.; Guy, J.; Hahn, C.; Harris, S.; Herrera, D.; Herrera-Alcantar, Hiram K.; Honscheid, K.; Howlett, C.; Huterer, D.; Iršič, V.; Ishak, M.; Jelinsky, P.; Jiang, L.; Jimenez, J.; Jing, Y. P.; Joyce, R.; Jullo, E.; Juneau, S.; Karaçaylı, N. G.; Karamanis, M.; Karcher, A.; Karim, T.; Kehoe, R.; Kent, S.; Kirkby, D.; Kisner, T.; Kitaura, F.; Koposov, S. E.; Kovács, A.; Kremin, A.; Krolewski, Alex; L'Huillier, B.; Lahav, O.; Lambert, A.; Lamman, C.; Lan, Ting-Wen; Landriau, M.; Lane, S.; Lang, D.; Lange, J. U.; Lasker, J.; Le Guillou, L.; Leauthaud, A.; Le Van Suu, A.; Levi, Michael E.; Li, T. S.; Magneville, C.; Manera, M.; Manser, Christopher J.; Marshall, B.; McCollam, W.; McDonald, P.; Meisner, Aaron M.; Mezcua, J. Mena-Fernández M.; Miller, T.; Miquel, R.; Montero-Camacho, P.; Moon, J.; Martini, J. Paul; Meneses-Rizo, J.; Moustakas, J.; Mueller, E.; Muñoz-Gutiérrez, Andrea; Myers, Adam D.; Nadathur, S.; Najita, J.; Napolitano, L.; Neilsen, E.; Newman, Jeffrey A.; Nie, J. D.; Ning, Y.; Niz, G.; Norberg, P.; Noriega, Hernán E.; O'Brien, T.; Obuljen, A.; Palanque-Delabrouille, N.; Palmese, A.; Zhiwei, P.; Pappalardo, D.; Peng, X.; Percival, W. J.; Perruchot, S.; Pogge, R.; Poppett, C.; Porredon, A.; Prada, F.; Prochaska, J.; Pucha, R.; Pérez-Fernández, A.; Pérez-Ráfols, I.; Rabinowitz, D.; Raichoor, A.; Ramirez-Solano, S.; Ramírez-Pérez, César; Ravoux, C.; Reil, K.; Rezaie, M.; Rocher, A.; Rockosi, C.; Roe, N. A.; Roodman, A.; Ross, A. J.; Rossi, G.; Ruggeri, R.; Ruhlmann-Kleider, V.; Sabiu, C. G.; Safonova, S.; Said, K.; Saintonge, A.; Salas Catonga, Javier; Samushia, L.; Sanchez, E.; Saulder, C.; Schaan, E.; Schlafly, E.; Schlegel, D.; Schmoll, J.; Scholte, D.; Schubnell, M.; Secroun, A.; Seo, H.; Serrano, S.; Sharples, Ray M.; Sholl, Michael J.; Silber, Joseph Harry; Silva, D. R.; Sirk, M.; Siudek, M.; Smith, A.; Sprayberry, D.; Staten, R.; Stupak, B.; Tan, T.; Tarlé, Gregory; Sien Tie, Suk; Tojeiro, R.; Ureña-López, L. A.; Valdes, F.; Valenzuela, O.; Valluri, M.; Vargas-Magaña, M.; Verde, L.; Walther, M.; Wang, B.; Wang, M. S.; Weaver, B. A.; Weaverdyck, C.; Wechsler, R.; Wilson, Michael J.; Yang, J.; Yu, Y.; Yuan, S.; Yèche, Christophe; Zhang, H.; Zhang, K.; Zhao, Cheng; Zhou, Rongpu; Zhou, Zhimin; Zou, H.; Zou, J.; Zou, S.; Zu, Y. Bibcode: 2022arXiv220510939A Altcode: The Dark Energy Spectroscopic Instrument (DESI) has embarked on an ambitious five-year survey to explore the nature of dark energy with spectroscopy of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the Baryon Acoustic Oscillation method to measure distances from the nearby universe to z > 3.5, as well as measure the growth of structure and probe potential modifications to general relativity. In this paper we describe the significant instrumentation we developed for the DESI survey. The new instrumentation includes a wide-field, 3.2-deg diameter prime-focus corrector that focuses the light onto 5020 robotic fiber positioners on the 0.812 m diameter, aspheric focal surface. The positioners and their fibers are divided among ten wedge-shaped petals. Each petal is connected to one of ten spectrographs via a contiguous, high-efficiency, nearly 50 m fiber cable bundle. The ten spectrographs each use a pair of dichroics to split the light into three channels that together record the light from 360 - 980 nm with a resolution of 2000 to 5000. We describe the science requirements, technical requirements on the instrumentation, and management of the project. DESI was installed at the 4-m Mayall telescope at Kitt Peak, and we also describe the facility upgrades to prepare for DESI and the installation and functional verification process. DESI has achieved all of its performance goals, and the DESI survey began in May 2021. Some performance highlights include RMS positioner accuracy better than 0.1", SNR per \sqrtÅ > 0.5 for a z > 2 quasar with flux 0.28e-17 erg/s/cm^2/A at 380 nm in 4000s, and median SNR = 7 of the [OII] doublet at 8e-17 erg/s/cm^2 in a 1000s exposure for emission line galaxies at z = 1.4 - 1.6. We conclude with highlights from the on-sky validation and commissioning of the instrument, key successes, and lessons learned. (abridged) Title: Classification of 11 supernovae by DEBass Authors: Lidman, C.; Dhaka, S.; Hall, M.; Melton, M.; Muller, E.; Ireland, M.; Sharp, R.; Abbot, H.; Armstrong, P.; Taylor, G.; Tucker, B. E.; Brout, D. Bibcode: 2021ATel14925....1L Altcode: We report spectroscopic classifications and redshifts of 11 supernovae observed by DEBass. The targets were supplied by ATLAS and ZTF. The spectra (350-900nm) were obtained with the WiFeS instrument (Dopita et al. 2007 Ap & SS, 327, 245) on the ANU 2.3-metre telescope. Title: Supernova 1987A: 3D Mixing and Light Curves for Explosion Models Based on Binary-merger Progenitors Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -Th.; Müller, E.; Ertl, T.; Menon, A.; Heger, A. Bibcode: 2021ApJ...914....4U Altcode: 2021arXiv210209686U Six binary-merger progenitors of supernova 1987A (SN 1987A) with properties close to those of the blue supergiant Sanduleak -69°202 are exploded by neutrino heating and evolved until long after shock breakout in 3D and continued for light-curve calculations in spherical symmetry. Our results confirm previous findings for single-star progenitors: (1) 3D neutrino-driven explosions with SN 1987A-like energies synthesize 56Ni masses consistent with the radioactive light-curve tail; (2) hydrodynamic models mix hydrogen inward to minimum velocities below 40 km s-1 compatible with spectral observations of SN 1987A; and (3) for given explosion energy the efficiency of outward radioactive 56Ni mixing depends mainly on high growth factors of Rayleigh-Taylor instabilities at the (C+O)/He and He/H composition interfaces and a weak interaction of fast plumes with the reverse shock occurring below the He/H interface. All binary-merger models possess presupernova radii matching the photometric radius of Sanduleak -69°202 and a structure of the outer layers allowing them to reproduce the observed initial luminosity peak in the first ~7 days. Models that mix about 0.5 M of hydrogen into the He-shell and exhibit strong outward mixing of 56Ni with maximum velocities exceeding the 3000 km s-1 observed for the bulk of ejected 56Ni have light-curve shapes in good agreement with the dome of the SN 1987A light curve. A comparative analysis of the best representatives of our 3D neutrino-driven explosion models of SN 1987A based on single-star and binary-merger progenitors reveals that only one binary model fulfills all observational constraints, except one. Title: Calibrating core overshooting parameters with two-dimensional hydrodynamical simulations Authors: Higl, J.; Müller, E.; Weiss, A. Bibcode: 2021A&A...646A.133H Altcode: 2020arXiv201205262H The extent of mixed regions around convective zones is one of the biggest uncertainties in stellar evolution. One-dimensional overshooting descriptions introduce a free parameter (fov) that is, in general, not well constrained from observations. Especially in small central convective regions, the value is highly uncertain due to its tight connection to the pressure scale height. Long-term multi-dimensional hydrodynamic simulations can be used to study the size of the overshooting region as well as the involved mixing processes. Here we show how one can calibrate an overshooting parameter by performing two-dimensional Maestro simulations of zero-age-main-sequence stars ranging from 1.3 to 3.5 M. The simulations cover the convective cores of the stars and a large fraction of the surrounding radiative envelope. We follow the convective flow for at least 20 convective turnover times, while the longest simulation covers 430 turnover time scales. This allows us to study how the mixing as well as the convective boundary itself evolve with time, and how the resulting entrainment can be interpreted in terms of overshooting parameters. We find that increasing the overshooting parameter fov beyond a certain value in the initial model of our simulations changes the mixing behaviour completely. This result can be used to put limits on the overshooting parameter. We find 0.010 < fov < 0.017 to be in good agreement with our simulations of a 3.5 M mass star. We also identify a diffusive mixing component due to internal gravity waves that is active throughout the convectively stable layer, but it is most likely overestimated in our simulations. Furthermore, applying our calibration method to simulations of less massive stars suggests a need for a mass-dependent overshooting description where the mixing in terms of the pressure scale height is reduced for small convective cores. Title: ESPRESSO high-resolution transmission spectroscopy of WASP-76 b Authors: Tabernero, H. M.; Zapatero Osorio, M. R.; Allart, R.; Borsa, F.; Casasayas-Barris, N.; Demangeon, O.; Ehrenreich, D.; Lillo-Box, J.; Lovis, C.; Pallé, E.; Sousa, S. G.; Rebolo, R.; Santos, N. C.; Pepe, F.; Cristiani, S.; Adibekyan, V.; Allende Prieto, C.; Alibert, Y.; Barros, S. C. C.; Bouchy, F.; Bourrier, V.; D'Odorico, V.; Dumusque, X.; Faria, J. P.; Figueira, P.; Génova Santos, R.; González Hernández, J. I.; Hojjatpanah, S.; Lo Curto, G.; Lavie, B.; Martins, C. J. A. P.; Martins, J. H. C.; Mehner, A.; Micela, G.; Molaro, P.; Nunes, N. J.; Poretti, E.; Seidel, J. V.; Sozzetti, A.; Suárez Mascareño, A.; Udry, S.; Aliverti, M.; Affolter, M.; Alves, D.; Amate, M.; Avila, G.; Bandy, T.; Benz, W.; Bianco, A.; Broeg, C.; Cabral, A.; Conconi, P.; Coelho, J.; Cumani, C.; Deiries, S.; Dekker, H.; Delabre, B.; Fragoso, A.; Genoni, M.; Genolet, L.; Hughes, I.; Knudstrup, J.; Kerber, F.; Landoni, M.; Lizon, J. L.; Maire, C.; Manescau, A.; Di Marcantonio, P.; Mégevand, D.; Monteiro, M.; Monteiro, M.; Moschetti, M.; Mueller, E.; Modigliani, A.; Oggioni, L.; Oliveira, A.; Pariani, G.; Pasquini, L.; Rasilla, J. L.; Redaelli, E.; Riva, M.; Santana-Tschudi, S.; Santin, P.; Santos, P.; Segovia, A.; Sosnowska, D.; Spanò, P.; Tenegi, F.; Iwert, O.; Zanutta, A.; Zerbi, F. Bibcode: 2021A&A...646A.158T Altcode: 2020arXiv201112197T
Aims: We report on ESPRESSO high-resolution transmission spectroscopic observations of two primary transits of the highly irradiated, ultra-hot Jupiter-sized planet, WASP-76b. We investigated the presence of several key atomic and molecular features of interest that may reveal the atmospheric properties of the planet.
Methods: We extracted two transmission spectra of WASP-76b with R ≈ 140 000 using a procedure that allowed us to process the full ESPRESSO wavelength range (3800-7880 Å) simultaneously. We observed that at a high signal-to-noise ratio, the continuum of ESPRESSO spectra shows `wiggles', which are likely caused by an interference pattern outside the spectrograph. To search for the planetary features, we visually analysed the extracted transmission spectra and cross-correlated the observations against theoretical spectra of different atomic and molecular species.
Results: The following atomic features are detected: Li I, Na I, Mg I, Ca II, Mn I, K I, and Fe I. All are detected with a confidence level between 9.2 σ (Na I) and 2.8 σ (Mg I). We did not detect the following species: Ti I, Cr I, Ni I, TiO, VO, and ZrO. We impose the following 1 σ upper limits on their detectability: 60, 77, 122, 6, 8, and 8 ppm, respectively.
Conclusions: We report the detection of Li I on WASP-76b for the first time. In addition, we confirm the presence of Na I and Fe I as previously reported in the literature. We show that the procedure employed in this work can detect features down to the level of ~0.1% in the transmission spectrum and ~10 ppm by means of a cross-correlation method. We discuss the presence of neutral and singly ionised features in the atmosphere of WASP-76b.

Based on guaranteed time observations collected at the European Southern Observatory under ESO programme 1102.C-0744 by the ESPRESSO Consortium. Title: The SEDIGISM survey: First Data Release and overview of the Galactic structure Authors: Schuller, F.; Urquhart, J. S.; Csengeri, T.; Colombo, D.; Duarte-Cabral, A.; Mattern, M.; Ginsburg, A.; Pettitt, A. R.; Wyrowski, F.; Anderson, L.; Azagra, F.; Barnes, P.; Beltran, M.; Beuther, H.; Billington, S.; Bronfman, L.; Cesaroni, R.; Dobbs, C.; Eden, D.; Lee, M. -Y.; Medina, S. -N. X.; Menten, K. M.; Moore, T.; Montenegro-Montes, F. M.; Ragan, S.; Rigby, A.; Riener, M.; Russeil, D.; Schisano, E.; Sanchez-Monge, A.; Traficante, A.; Zavagno, A.; Agurto, C.; Bontemps, S.; Finger, R.; Giannetti, A.; Gonzalez, E.; Hernandez, A. K.; Henning, T.; Kainulainen, J.; Kauffmann, J.; Leurini, S.; Lopez, S.; Mac-Auliffe, F.; Mazumdar, P.; Molinari, S.; Motte, F.; Muller, E.; Nguyen-Luong, Q.; Parra, R.; Perez-Beaupuits, J. -P.; Schilke, P.; Schneider, N.; Suri, S.; Testi, L.; Torstensson, K.; Veena, V. S.; Venegas, P.; Wang, K.; Wienen, M. Bibcode: 2021MNRAS.500.3064S Altcode: 2020arXiv201201527S; 2020MNRAS.tmp.2600S; 2020MNRAS.500.3064S The SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium) survey used the APEX telescope to map 84 deg2 of the Galactic plane between ℓ = -60° and +31° in several molecular transitions, including 13CO (2 - 1) and C18O (2 - 1), thus probing the moderately dense (∼103 cm-3) component of the interstellar medium. With an angular resolution of 30 arcsec and a typical 1σ sensitivity of 0.8-1.0 K at 0.25 km s-1 velocity resolution, it gives access to a wide range of structures, from individual star-forming clumps to giant molecular clouds and complexes. The coverage includes a good fraction of the first and fourth Galactic quadrants, allowing us to constrain the large-scale distribution of cold molecular gas in the inner Galaxy. In this paper, we provide an updated overview of the full survey and the data reduction procedures used. We also assess the quality of these data and describe the data products that are being made publicly available as part of this First Data Release (DR1). We present integrated maps and position-velocity maps of the molecular gas and use these to investigate the correlation between the molecular gas and the large-scale structural features of the Milky Way such as the spiral arms, Galactic bar and Galactic Centre. We find that approximately 60 per cent of the molecular gas is associated with the spiral arms and these appear as strong intensity peaks in the derived Galactocentric distribution. We also find strong peaks in intensity at specific longitudes that correspond to the Galactic Centre and well-known star-forming complexes, revealing that the 13CO emission is concentrated in a small number of complexes rather than evenly distributed along spiral arms. Title: The SEDIGISM survey: molecular clouds in the inner Galaxy Authors: Duarte-Cabral, A.; Colombo, D.; Urquhart, J. S.; Ginsburg, A.; Russeil, D.; Schuller, F.; Anderson, L. D.; Barnes, P. J.; Beltrán, M. T.; Beuther, H.; Bontemps, S.; Bronfman, L.; Csengeri, T.; Dobbs, C. L.; Eden, D.; Giannetti, A.; Kauffmann, J.; Mattern, M.; Medina, S. -N. X.; Menten, K. M.; Lee, M. -Y.; Pettitt, A. R.; Riener, M.; Rigby, A. J.; Traficante, A.; Veena, V. S.; Wienen, M.; Wyrowski, F.; Agurto, C.; Azagra, F.; Cesaroni, R.; Finger, R.; Gonzalez, E.; Henning, T.; Hernandez, A. K.; Kainulainen, J.; Leurini, S.; Lopez, S.; Mac-Auliffe, F.; Mazumdar, P.; Molinari, S.; Motte, F.; Muller, E.; Nguyen-Luong, Q.; Parra, R.; Perez-Beaupuits, J. -P.; Montenegro-Montes, F. M.; Moore, T. J. T.; Ragan, S. E.; Sánchez-Monge, A.; Sanna, A.; Schilke, P.; Schisano, E.; Schneider, N.; Suri, S.; Testi, L.; Torstensson, K.; Venegas, P.; Wang, K.; Zavagno, A. Bibcode: 2021MNRAS.500.3027D Altcode: 2020MNRAS.tmp.2609D; 2020arXiv201201502D; 2020MNRAS.500.3027D We use the 13CO (2-1) emission from the SEDIGISM (Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) high-resolution spectral-line survey of the inner Galaxy, to extract the molecular cloud population with a large dynamic range in spatial scales, using the Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) algorithm. This work compiles a cloud catalogue with a total of 10 663 molecular clouds, 10 300 of which we were able to assign distances and compute physical properties. We study some of the global properties of clouds using a science sample, consisting of 6664 well-resolved sources and for which the distance estimates are reliable. In particular, we compare the scaling relations retrieved from SEDIGISM to those of other surveys, and we explore the properties of clouds with and without high-mass star formation. Our results suggest that there is no single global property of a cloud that determines its ability to form massive stars, although we find combined trends of increasing mass, size, surface density, and velocity dispersion for the sub-sample of clouds with ongoing high-mass star formation. We then isolate the most extreme clouds in the SEDIGISM sample (i.e. clouds in the tails of the distributions) to look at their overall Galactic distribution, in search for hints of environmental effects. We find that, for most properties, the Galactic distribution of the most extreme clouds is only marginally different to that of the global cloud population. The Galactic distribution of the largest clouds, the turbulent clouds and the high-mass star-forming clouds are those that deviate most significantly from the global cloud population. We also find that the least dynamically active clouds (with low velocity dispersion or low virial parameter) are situated further afield, mostly in the least populated areas. However, we suspect that part of these trends may be affected by some observational biases (such as completeness and survey limitations), and thus require further follow up work in order to be confirmed. Title: A precise architecture characterization of the π Mensae planetary system Authors: Damasso, M.; Sozzetti, A.; Lovis, C.; Barros, S. C. C.; Sousa, S. G.; Demangeon, O. D. S.; Faria, J. P.; Lillo-Box, J.; Cristiani, S.; Pepe, F.; Rebolo, R.; Santos, N. C.; Zapatero Osorio, M. R.; González Hernández, J. I.; Amate, M.; Pasquini, L.; Zerbi, F. M.; Adibekyan, V.; Abreu, M.; Affolter, M.; Alibert, Y.; Aliverti, M.; Allart, R.; Allende Prieto, C.; Álvarez, D.; Alves, D.; Avila, G.; Baldini, V.; Bandy, T.; Benz, W.; Bianco, A.; Borsa, F.; Bossini, D.; Bourrier, V.; Bouchy, F.; Broeg, C.; Cabral, A.; Calderone, G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.; Cupani, G.; D'Odorico, V.; Deiries, S.; Dekker, H.; Delabre, B.; Di Marcantonio, P.; Dumusque, X.; Ehrenreich, D.; Figueira, P.; Fragoso, A.; Genolet, L.; Genoni, M.; Génova Santos, R.; Hughes, I.; Iwert, O.; Kerber, F.; Knudstrup, J.; Landoni, M.; Lavie, B.; Lizon, J. -L.; Lo Curto, G.; Maire, C.; Martins, C. J. A. P.; Mégevand, D.; Mehner, A.; Micela, G.; Modigliani, A.; Molaro, P.; Monteiro, M. A.; Monteiro, M. J. P. F. G.; Moschetti, M.; Mueller, E.; Murphy, M. T.; Nunes, N.; Oggioni, L.; Oliveira, A.; Oshagh, M.; Pallé, E.; Pariani, G.; Poretti, E.; Rasilla, J. L.; Rebordão, J.; Redaelli, E. M.; Riva, M.; Santana Tschudi, S.; Santin, P.; Santos, P.; Ségransan, D.; Schmidt, T. M.; Segovia, A.; Sosnowska, D.; Spanò, P.; Suárez Mascareño, A.; Tabernero, H.; Tenegi, F.; Udry, S.; Zanutta, A. Bibcode: 2020A&A...642A..31D Altcode: 2020arXiv200706410D Context. The bright star π Men was chosen as the first target for a radial velocity follow-up to test the performance of ESPRESSO, the new high-resolution spectrograph at the European Southern Observatory's Very Large Telescope. The star hosts a multi-planet system (a transiting 4 M planet at ~0.07 au and a sub-stellar companion on a ~2100-day eccentric orbit), which is particularly suitable for a precise multi-technique characterization.
Aims: With the new ESPRESSO observations, which cover a time span of 200 days, we aim to improve the precision and accuracy of the planet parameters and search for additional low-mass companions. We also take advantage of the new photometric transits of π Men c observed by TESS over a time span that overlaps with that of the ESPRESSO follow-up campaign.
Methods: We analysed the enlarged spectroscopic and photometric datasets and compared the results to those in the literature. We further characterized the system by means of absolute astrometry with HIPPARCOS and Gaia. We used the high-resolution spectra of ESPRESSO for an independent determination of the stellar fundamental parameters.
Results: We present a precise characterization of the planetary system around π Men. The ESPRESSO radial velocities alone (37 nightly binned data with typical uncertainty of 10 cm s-1) allow for a precise retrieval of the Doppler signal induced by π Men c. The residuals show a root mean square of 1.2 m s-1, which is half that of the HARPS data; based on the residuals, we put limits on the presence of additional low-mass planets (e.g. we can exclude companions with a minimum mass less than ~2 M within the orbit of π Men c). We improve the ephemeris of π Men c using 18 additional TESS transits, and, in combination with the astrometric measurements, we determine the inclination of the orbital plane of π Men b with high precision (ib =45.8-1.1+1.4 deg). This leads to the precise measurement of its absolute mass mb =14.1-0.4+0.5 MJup, indicating that π Men b can be classified as a brown dwarf.
Conclusions: The π Men system represents a nice example of the extreme precision radial velocities that can be obtained with ESPRESSO for bright targets. Our determination of the 3D architecture of the π Men planetary system and the high relative misalignment of the planetary orbital planes put constraints on and challenge the theories of the formation and dynamical evolution of planetary systems. The accurate measurement of the mass of π Men b contributes to make the brown dwarf desert a bit greener.

Tables B.1 and B.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/642/A31

Based (in part) on Guaranteed Time Observations collected at the European Southern Observatory (ESO) under ESO programme(s) 1102.C-0744, 1102.C-0958, and 1104.C-0350 by the ESPRESSO Consortium. Title: Characterization of the K2-38 planetary system. Unraveling one of the densest planets known to date Authors: Toledo-Padrón, B.; Lovis, C.; Suárez Mascareño, A.; Barros, S. C. C.; González Hernández, J. I.; Sozzetti, A.; Bouchy, F.; Zapatero Osorio, M. R.; Rebolo, R.; Cristiani, S.; Pepe, F. A.; Santos, N. C.; Sousa, S. G.; Tabernero, H. M.; Lillo-Box, J.; Bossini, D.; Adibekyan, V.; Allart, R.; Damasso, M.; D'Odorico, V.; Figueira, P.; Lavie, B.; Lo Curto, G.; Mehner, A.; Micela, G.; Modigliani, A.; Nunes, N. J.; Pallé, E.; Abreu, M.; Affolter, M.; Alibert, Y.; Aliverti, M.; Allende Prieto, C.; Alves, D.; Amate, M.; Avila, G.; Baldini, V.; Bandy, T.; Benatti, S.; Benz, W.; Bianco, A.; Broeg, C.; Cabral, A.; Calderone, G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.; Cupani, G.; Deiries, S.; Dekker, H.; Delabre, B.; Demangeon, O.; Di Marcantonio, P.; Ehrenreich, D.; Fragoso, A.; Genolet, L.; Genoni, M.; Génova Santos, R.; Hughes, I.; Iwert, O.; Knudstrup, J.; Landoni, M.; Lizon, J. L.; Maire, C.; Manescau, A.; Martins, C. J. A. P.; Mégevand, D.; Molaro, P.; Monteiro, M. J. P. F. G.; Monteiro, M. A.; Moschetti, M.; Mueller, E.; Oggioni, L.; Oliveira, A.; Oshagh, M.; Pariani, G.; Pasquini, L.; Poretti, E.; Rasilla, J. L.; Redaelli, E.; Riva, M.; Santana Tschudi, S.; Santin, P.; Santos, P.; Segovia, A.; Sosnowska, D.; Spanò, P.; Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, F. Bibcode: 2020A&A...641A..92T Altcode: 2020arXiv200701081T Context. An accurate characterization of the known exoplanet population is key to understanding the origin and evolution of planetary systems. Determining true planetary masses through the radial velocity (RV) method is expected to experience a great improvement thanks to the availability of ultra-stable echelle spectrographs.
Aims: We took advantage of the extreme precision of the new-generation echelle spectrograph ESPRESSO to characterize the transiting planetary system orbiting the G2V star K2-38 located at 194 pc from the Sun with V ~ 11.4. This system is particularly interesting because it could contain the densest planet detected to date.
Methods: We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets, K2-38b and K2-38c, with Pb = 4.01593 ± 0.00050 d and Pc = 10.56103 ± 0.00090 d, respectively. Using 43 ESPRESSO high-precision RV measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a Markov chain Monte Carlo analysis, significantly improving their mass measurements.
Results: Using ESPRESSO spectra, we derived the stellar parameters, Teff = 5731 ± 66, log g = 4.38 ± 0.11 dex, and [Fe/H] = 0.26 ± 0.05 dex, and thus the mass and radius of K2-38, M = 1.03-0.02+0.04 M and R = 1.06-0.06+0.09 R. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with RP = 1.54 ± 0.14 R and Mp = 7.3-1.0+1.1 M, and K2-38c as a sub-Neptune with RP = 2.29 ± 0.26 R and Mp = 8.3-1.3+1.3 M. Combining the radius and mass measurements, we derived a mean density of ρp = 11.0-2.8+4.1 g cm-3 for K2-38b and ρp = 3.8-1.1+1.8 g cm-3 for K2-38c, confirming K2-38b as one of the densest planets known to date.
Conclusions: The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky-model with H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the RV time-series whose origin could be linked to a 0.25-3 MJ planet or stellar activity.

The ESPRESSO RVs used in this paper are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/641/A92

Based (in part) on Guaranteed Time Observations collected at the European Southern Observatory under ESO programmes1102.C-0744, 112.C-0958, and 1104.C-0350 by the ESPRESSO Consortium. Title: VizieR Online Data Catalog: pi Men radial velocity curves (Damasso+, 2020) Authors: Damasso, M.; Sozzetti, A.; Lovis, C.; Barros, S. C. C.; Sousa, S. G.; Demangeon, O. D. S.; Faria, J. P.; Lillo-Box, J.; Cristiani, S.; Pepe, F.; Rebolo, R.; Santos, N. C.; Zapatero Osorio, M. R.; Gonzalez Hernandez, J. I.; Amate, M.; Pasquini, L.; Zerbi, F. M.; Adibekyan, V.; Abreu, M.; Aolter, M.; Alibert, Y.; Aliverti, M.; Allart, R.; Allende Prieto, C.; Alvarez, D.; Alves, D.; Avila, G.; Baldini, V.; Bandy, T.; Benz, W.; Bianco, A.; Borsa, F.; Bossini, D.; Bourrier, V.; Bouchy, F.; Broeg, C.; Cabral, A.; Calderone, G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.; Cupani, G.; D'Odorico, V.; Deiries, S.; Dekker, H.; Delabre, B.; di Marcantonio, P.; Dumusque, X.; Ehrenreich, D.; Figueira, P.; Fragoso, A.; Genolet, L.; Genoni, M.; Genova Santos, R.; Hughes, I.; Iwert, O.; F. Kerber; Knudstrup, J.; Landoni, M.; Lavie, B.; Lizon, J. -L.; Lo Curto, G.; Maire, C.; J. A. P. Martins, C.; Megevand, D.; Mehner, A.; Micela, G.; Modigliani, A.; Molaro, P.; Monteiro, M. A.; Monteiro, M. J. P. F. G.; Moschetti, M.; Mueller, E.; Murphy, M. T.; Nunes, N.; Oggioni, L.; Olive, Ira A.; Oshagh, M.; Palle, E.; Pariani, G.; Poretti, E.; Rasilla, J. L.; Rebordao, J.; Redaelli, E. M.; Riva, M.; Santana Tschudi, S.; Santin, P.; Santos, P.; Segransan, D.; Schmidt, T. M.; Segovia, A.; Sosnowska, D.; Spano, P.; Suarez Mascareno, A.; Tabernero, H.; Tenegi, F.; Udry, S.; Zanutta, A. Bibcode: 2020yCat..36420031D Altcode: The observations of pi Men with ESPRESSO (using the instrument in single Unit Telescope mode with a median resolving power R=138000 over the 378.2 and 788.7nm wavelength range) were carried out within one of the sub-programmes of the Guaranteed Time Observations (GTOs), aimed at using the very precise RVs to characterize (i.e. measure masses and bulk densities) transiting planets discovered by TESS and Kepler's second light K2 mission (see Pepe et al. 2020 (A&A, submitted) for a detailed discussion of the ESPRESSO on-sky performance). The pi Men system was observed starting from September 2018, right before the end of the commissioning phase of the instrument, up to March 2019. We collected 275 spectra over 37 nights (multiple and consecutive exposures per night) during a total time span of 201 days. The spectra were acquired with a typical exposure time of 120s, providing a median signal-to-noise ratio S/N=243 per extracted pixel at λ=500nm. In this work we also use previously unreleased spectra from CORALIE to extract additional RVs. The pi Men system was observed with CORALIE from November 1998 to February 2020, during which time 60 spectra with typical exposure times of 300-600s (S/N=82-124 at 550nm) were collected.

Radial velocities extracted from ESPRESSO and CORALIE spectra, and spectroscopic stellar activity diagnostics from ESPRESSO.

(2 data files). Title: Revisiting Proxima with ESPRESSO Authors: Suárez Mascareño, A.; Faria, J. P.; Figueira, P.; Lovis, C.; Damasso, M.; González Hernández, J. I.; Rebolo, R.; Cristiani, S.; Pepe, F.; Santos, N. C.; Zapatero Osorio, M. R.; Adibekyan, V.; Hojjatpanah, S.; Sozzetti, A.; Murgas, F.; Abreu, M.; Affolter, M.; Alibert, Y.; Aliverti, M.; Allart, R.; Allende Prieto, C.; Alves, D.; Amate, M.; Avila, G.; Baldini, V.; Bandi, T.; Barros, S. C. C.; Bianco, A.; Benz, W.; Bouchy, F.; Broeng, C.; Cabral, A.; Calderone, G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.; Cupani, G.; D'Odorico, V.; Deiries, S.; Delabre, B.; Di Marcantonio, P.; Dumusque, X.; Ehrenreich, D.; Fragoso, A.; Genolet, L.; Genoni, M.; Génova Santos, R.; Hughes, I.; Iwert, O.; Kerber, F.; Knusdstrup, J.; Landoni, M.; Lavie, B.; Lillo-Box, J.; Lizon, J.; Lo Curto, G.; Maire, C.; Manescau, A.; Martins, C. J. A. P.; Mégevand, D.; Mehner, A.; Micela, G.; Modigliani, A.; Molaro, P.; Monteiro, M. A.; Monteiro, M. J. P. F. G.; Moschetti, M.; Mueller, E.; Nunes, N. J.; Oggioni, L.; Oliveira, A.; Pallé, E.; Pariani, G.; Pasquini, L.; Poretti, E.; Rasilla, J. L.; Redaelli, E.; Riva, M.; Santana Tschudi, S.; Santin, P.; Santos, P.; Segovia, A.; Sosnowska, D.; Sousa, S.; Spanò, P.; Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, F. Bibcode: 2020A&A...639A..77S Altcode: 2020arXiv200512114S Context. The discovery of Proxima b marked one of the most important milestones in exoplanetary science in recent years. Yet the limited precision of the available radial velocity data and the difficulty in modelling the stellar activity calls for a confirmation of the Earth-mass planet.
Aims: We aim to confirm the presence of Proxima b using independent measurements obtained with the new ESPRESSO spectrograph, and refine the planetary parameters taking advantage of its improved precision.
Methods: We analysed 63 spectroscopic ESPRESSO observations of Proxima (Gl 551) taken during 2019. We obtained radial velocity measurements with a typical radial velocity photon noise of 26 cm s-1. We combined these data with archival spectroscopic observations and newly obtained photometric measurements to model the stellar activity signals and disentangle them from planetary signals in the radial velocity (RV) data. We ran a joint Markov chain Monte Carlo analysis on the time series of the RV and full width half maximum of the cross-correlation function to model the planetary and stellar signals present in the data, applying Gaussian process regression to deal with the stellar activity signals.
Results: We confirm the presence of Proxima b independently in the ESPRESSO data and in the combined ESPRESSO+ HARPS+UVES dataset. The ESPRESSO data on its own shows Proxima b at a period of 11.218 ± 0.029 days, with a minimum mass of 1.29 ± 0.13 M. In the combined dataset we measure a period of 11.18427 ± 0.00070 days with a minimum mass of 1.173 ± 0.086 M. We get a clear measurement of the stellar rotation period (87 ± 12 d) and its induced RV signal, but no evidence of stellar activity as a potential cause for the 11.2 days signal. We find some evidence for the presence of a second short-period signal, at 5.15 days with a semi-amplitude of only 40 cm s-1. If caused by a planetary companion, it would correspond to a minimum mass of 0.29 ± 0.08 M. We find that forthe case of Proxima, the full width half maximum of the cross-correlation function can be used as a proxy for the brightness changes and that its gradient with time can be used to successfully detrend the RV data from part of the influence of stellar activity. The activity-induced RV signal in the ESPRESSO data shows a trend in amplitude towards redder wavelengths. Velocities measured using the red end of the spectrograph are less affected by activity, suggesting that the stellar activity is spot dominated. This could be used to create differential RVs that are activity dominated and can be used to disentangle activity-induced and planetary-induced signals. The data collected excludes the presence of extra companions with masses above 0.6 M at periods shorter than 50 days.

The data used in this paper are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/639/A77

Based [in part] on Guaranteed Time Observations collected at the European Southern Observatory under ESO programme 1102.C-0744. by the ESPRESSO Consortium.

This work makes use of observations from the LCOGT network. Title: VizieR Online Data Catalog: K2-38 ESPRESSO RVs (Toledo-Padron+, 2020) Authors: Toledo-Padron B. . Lovis, C.; Suarez Mascareno, A.; Barros, S. C. C.; Gonzalez Hernandez, J. I.; Sozzetti, A.; Bouchy, F.; Zapatero Osorio, M. R.; Rebolo, R.; Cristiani, S.; Pepe, F. A.; Santos, N. C.; Sousa, S. G.; Tabernero, H. M.; Lillo-Box, J.; Bossini, D.; Adibekyan, V.; Allart, R.; Damasso, M.; D'Odorico, V.; Figueira, P.; Lavie, B.; Lo Curto, G.; Mehner, A.; Micela, G.; Modigliani, A.; Nunes, N. J.; Palle, E.; Abreu, M.; Affolter, M.; Alibert, Y.; Aliverti, M.; Allende Prieto, C.; Alves, D.; Amate, M.; Avila, G.; Baldini, V.; Bandy, T.; Benatti, S.; Benz, W.; Bianco, A.; Broeg, C.; Cabral, A.; Calderone, G.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cumani, C.; Cupani, G.; Deiries, S.; Dekker, H.; Delabre, B.; Demangeon, O.; di Marcantonio, P.; Ehrenreich, D.; Fragoso, A.; Genolet, L.; Genoni, M.; Genova Santos, R.; Hughes, I.; Iwert, O.; Knudstrup, J.; Landoni, M.; Lizon, J. L.; Maire, C.; Manescau, A.; Martins, C. J. A. P.; Megevand, D.; Molaro, P.; Monteiro, M. J. P. F. G.; Monteiro, M. A.; Moschetti, M.; Mueller, E.; Oggioni, L.; Oliveira, A.; O'Shagh, M.; Pariani, G.; Pasquini, L.; Poretti, E.; Rasilla, J. L.; Redaelli, E.; Riva, M.; Santana Tschudi, S.; Santin, P.; Santos, P.; Segovia, A.; Sosnowska, D.; Spano, P.; Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, F. Bibcode: 2020yCat..36410092T Altcode: We used the public version of the ESPRESSO pipeline Data-Reduction-Software (DRS) to compute the RVs of K2-38. The pipeline provides a crosscorrelation function (CCF) for each spectrum using a G2 mask that covers the entire wavelength range of the instrument (between 3800 and 7880Å). The CCFs were built using a RV step of 0.5km/s within a range between -55 and -15km/s centered on the systemic velocity of the star. This RV time-series presents a RV precision of 1.0m/s with a RMS of 3.6m/s, an extremely good result for a relatively faint G2 star (V=11.34) like K2-38.

(1 data file). Title: The origin of continental carbonates in Andean salars: A multi-tracer geochemical approach in Laguna Pastos Grandes (Bolivia) Authors: Muller, E.; Gaucher, E. C.; Durlet, C.; Moquet, J. S.; Moreira, M.; Rouchon, V.; Louvat, P.; Bardoux, G.; Noirez, S.; Bougeault, C.; Vennin, E.; Gérard, E.; Chavez, M.; Virgone, A.; Ader, M. Bibcode: 2020GeCoA.279..220M Altcode: In continental volcanic settings, abundant carbonate precipitation can occur with atypical facies compared to marine settings. The (bio-)chemical processes responsible for their development and early diagenesis are typically complex and not fully understood. In the Bolivian Altiplano, Laguna Pastos Grandes hosts a 40-km2 carbonate platform with a great diversity of facies and provides an ideal natural laboratory to understand the processes responsible for the precipitation of carbonates in a continental province dominated by volcanism. In order to trace the origin of both water and solutes in the lagoon, the major element and stable isotope compositions (δ2H-δ18O, δ37Cl, δ7Li, δ11B and 87Sr/86Sr) of the spring and stream waters were characterized, as well as the stable isotope compositions (δ13C, δ15N) and noble gas isotope ratios of hydrothermal gases associated with spring waters. The results show that thermal springs discharging on the carbonate platform are close to saturation with calcite. PHREEQC modeling, together with fluid geochemistry and temperature estimated from a combination of geothermometers, indicate that Ca in these springs is inherited from the alteration of the volcanic bedrock by aqueous fluids heated at ∼225 °C and enriched in magmatic mantle-derived CO2. Our results clearly show that the main driver for the precipitation of modern carbonates in Laguna Pastos Grandes is the deeply sourced CO2, which boosts the alteration of volcanic rocks at depth. Title: VizieR Online Data Catalog: Proxima Cen RV, FWHM and fluxes (Suarez Mascareno+, 2020) Authors: Suarez Mascareno, A.; Faria, J. P.; Figueira, P.; Lovis, C.; Damasso, M.; Gonzalez Hernandez, J. I.; Rebolo, R.; Cristiano, S.; Pepe, F.; Santos, N. C.; Zapatero Osorio, M. R.; Adibekyan, V.; Hojjatpanah, S.; Sozzetti, A.; Murgas, F.; Abreu, M.; Affolter, M.; Alibert, Y.; Aliverti, M.; Allart, R.; Allende Prieto, C.; Alves, D.; Amate, M.; Avila, G.; Baldini, V.; Bandi, T.; Barros, S. C. C.; Bianco, A.; Benz, W.; Bouchy, F.; Broeng, C.; Cabral, A.; Calderone, G.; Cirami, R.; Coleho, J.; Conconi, P.; Coretti, I.; Cumani, C.; Cupani, G.; D Odorico, V.; Deiries, S.; Delabre, B.; di Marcantonio, P.; Dumusque, X.; Ehrenreich, D.; Fragoso, A.; Genolet, L.; Genoni, M.; Genova Santos, R.; Hughes, I.; Iwert, O.; Kerber, F.; Knusdrtrup, J.; Landoni, M.; Lavie, B.; Lillo-Box, J.; Lizon, J.; Lo Curto, G.; Maire, C.; Manescau, A.; Martins, C. J. A. P.; Megevand, D.; Mehner, A.; Micela, G.; Modigliani, A.; Molaro, P.; Monteiro, M. A.; Monteiro, M. J. P. F. G.; Moschetti, M.; Mueller, E.; Nunes, N. J.; Oggioni, L.; Oliveira, A.; Palle, E.; Pariani, G.; Pasquini, L.; Poretti E!, .; Rasill, A. J. L.; Redaelli, E.; Riva, M.; Santana Tschudi, S.; Santin, P.; Santos, P.; Segovia, A.; Sosnowska, D.; Sousa, S.; Snano, P.; Tenegi, F.; Udry, S.; Zanutta, A.; Zerbi, F. Bibcode: 2020yCat..36390077S Altcode: We obtained 67 individual spectra as part of the ESPRESSO GTO, as part of programme ID 1102.C-744 (PI: F.Pepe). Measurements were taken in ESPRESSO's 1UT high resolution (HR) mode with 15 minutes of integration time. More information on the different observing modes can be found on the ESO instrument page. ESPRESSO is equipped with its own pipeline providing extracted and wavelength-calibrated spectra, as well as RV measurements. The RV measurements are determined by a Gaussian fit of the cross-correlation function (CCF) of the spectrum with a binary mask computed from a stellar template. The mask was created using an ESPRESSO spectrum of Proxima as a template. Lines were identified through an automatic line-searching algorithm based on the spectrum derivative. The pipeline, version 2.0.0, is fully available to download from the ESO pipeline website.

In combination with the ESPRESSO data we include the measurements taken between 2003 and 2017 with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph. These data where obtained by the Geneva/Grenoble survey and the RedDots project, under programmes 072.C-0488, 082.C-0718, 183.C-0437, 191.C-0505, 096.C-0082, 099.C-0205, and 099.C-0880. This dataset is comprised of 196 individual measurements that include two high cadence campaigns in 2016 and 2017. The RVs were calculated using the TERRA package and have been obtained from. In 2015 HARPS was updated with new fibres, which improved its stability but also caused an RV offset with respect to previous measurements. For this reason we treat both HARPS datasets independently. The majority of the data were obtained without simultaneous calibration, which limits the stability of HARPS to a level of 1m/s.

Along with the previous data we include the RVs taken with the Ultraviolet and Visual Echelle Spectrograph (UVES) and analysed in Dmasso et al. 2020. This dataset consists of 77 nightly binned UVES RVs obtained between 2000 and 2007. The UVES data were obtained in one of the early RV surveys for planets around M-dwarfs under ESO programme IDs: 65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415, 69.C-0722, 70.C-0044, 71.C-0498, 072.C-0495, 173.C-0606, and 078.C-0829 (PI: M. Kuerster). The data reduction and RV measurement is described in Butler et al., 2019AJ....158..251B. Cat. J/AJ/158/251). The UVES data do not include a measurement of the FWHM, as it is not easily available due to calibration by the iodine gas absorption cell.

(3 data files). Title: Impact of SDSS Clustering Measurements on the Cosmological Model Authors: Mueller, E.; eBOSS Collaboration; Dawson, K.; Bautista, J.; de Mattia, A.; Rossi, G.; Hou, J.; Zarrouk, P.; Percival, W. Bibcode: 2020AAS...23541307M Altcode: In the past decades, understanding the cosmic expansion and growth of structure of our Universe has been the primary focus of cosmological research. Large scale structure measurements of BAO and RSD are crucial to improve our knowledge of the underlying physical mechanisms that govern our Universe as well as to test the predictions of the LCDM (Lambda Cold Dark Matter) model, the standard cosmological model. In this talk, I present the cosmological implications of the final BOSS and eBOSS spectroscopic programs including constraints on dark energy and massive neutrinos. Title: N-Body Simulations and Model Testing Authors: Rossi, G.; Dawson, K.; Percival, W.; Bautista, J.; de Mattia, A.; Hou, J.; Zarrouk, P.; Mueller, E. Bibcode: 2020AAS...23541304R Altcode: Quantifying the systematic error budget in redshift space distortion measurements from galaxy surveys is an essential step towards the determination of unbiased estimates of the cosmic growth rate. We developed a set of mock data challenges (including a blind series) to simulate clustering studies with eBOSS Luminous Red Galaxies, Emission Line Galaxies, and Quasars. The data challenge catalogs were based on high-fidelity mocks constructed from state-of-the-art N-body simulations such as the Outer Rim. In this talk, I will present results from those mock challenges and I will quantify the systematic error budget for the final growth estimates in eBOSS. I will also briefly touch upon the novel series of EZmocks, critical to quantifying the precision of the final eBOSS clustering results. Results from our study have broader application, as similar mock-making techniques and systematic corrections will be applied to DESI galaxy and quasar clustering studies. Title: Introduction: the Extended Baryon Spectroscopic Survey Authors: Dawson, K. S.; Percival, W.; Bautista, J.; Hou, J.; de Mattia, A.; Mueller, E.; Myers, A.; Rossi, G.; Zarrouk, P.; Zhao, G. Bibcode: 2020AAS...23541301D Altcode: The Extended Baryon Oscillation Spectroscopic Survey (eBOSS) concluded observations of the cosmic distance scale and the growth of structure in February, 2019. The full sample of galaxy surveys within the Sloan Digital Sky Survey allows an exploration of Baryon Acoustic Oscillations (BAO) and redshift-space distortions (RSD) out to redshifts z < 3.5. I will present an overview of the survey and observational techniques as an introduction to the special session on final eBOSS results. Title: Emission Line Galaxies as a Distinct Tracer Authors: de Mattia, A.; Bautista, J.; Dawson, K.; Hou, J.; Mueller, E.; Percival, W. J.; Rossi, G.; Zarrouk, P.; Zhao, G. Bibcode: 2020AAS...23541303D Altcode: The Emission Line Galaxy (ELG) sample of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) is one of the two largest ELG catalogs to date with its 170,000 galaxies. Designed to probe galaxies at high redshift (0.6 < z < 1.1) and at high density, this program is a pathfinder to next generation spectroscopic surveys such as the Dark Energy Spectroscopic Instrument (DESI), which will probe 100 times more galaxies. In this talk, I will explain how the ELG photometric selection impacts the clustering signal and present the various analysis techniques developed to ensure robust cosmological measurements. To conclude, I will present the best estimates derived for the growth rate of structure and lessons for future galaxy surveys. Title: GRAVITY and the Galactic Centre Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...26G Altcode: On a clear night, our home galaxy, the Milky Way, is visible as a starry ribbon across the sky. Its core is located in the constellation of Sagittarius, approximately where the bright glow is interrupted by the darkest dust filaments. There, hidden, lies a massive black hole. To peer through the obscuring clouds and see the stars and gas near the black hole we use GRAVITY. The main GRAVITY results are the detection of gra- vitational redshift, the most precise mass- distance measurement, the test of the equivalence principle, and the detection of orbital motion near the black hole. Title: An Image of the Dust Sublimation Region in the Nucleus of NGC 1068 Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...24G Altcode: The superb resolution of the Very Large Telescope Interferometer (VLTI) and the unrivalled sensitivity of GRAVITY have allowed us to reconstruct the first detailed image of the dust sublimation region in an active galaxy. In the nearby archetypal Seyfert 2 galaxy NGC 1068, the 2 µm continuum emission traces a highly inclined thin ring-like structure with a radius of 0.24 pc. The observed morphology challenges the picture of a geometrically and optically thick torus. Title: Spatially Resolved Accretion-Ejection in Compact Binaries with GRAVITY Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...29G Altcode: The GRAVITY instrument at the Very Large Telescope Interferometer has led to the first spatially resolved observations of X-ray binaries at scales comparable to the binary orbit, providing unprecedented spatial information on their accretion-ejection mechanisms. In particular, observations of the hypercritical accretor SS433 have revealed a variety of spatial structures at the heart of this exotic microquasar, including bipolar outflows, super-Keplerian equatorial outflows and extended baryonic jets photoionised by collimated ultraviolet radiation. Title: Hunting Exoplanets with Single-Mode Optical Interferometry Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...47G Altcode: The GRAVITY instrument was primarily conceived for imaging and astrometry of the Galactic centre. However, its sensitivity and astrometric capabilities have also enabled interferometry to reach a new domain of astrophysics: exoplanetology. In March 2019, the GRAVITY collaboration published the first spectrum and astrometry of an exoplanet obtained by optical interferometry. In this article, we show how this observation is paving the way to even more exciting discoveries — finding new planets, and characterising their atmospheres. Title: Spatially Resolving the Inner Gaseous Disc of the Herbig Star 51 Oph through its CO Ro-vibration Emission Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...40G Altcode: Near-infrared interferometry gives us the opportunity to spatially resolve the circumstellar environment of young stars at sub-astronomical-unit (au) scales, which a standalone telescope could not reach. In particular, the sensitivity of GRAVITY on the VLTI allows us to spatially resolve the CO overtone emission at 2.3 microns. In this article, we present a new method of using the model of the CO spectrum to reconstruct the differential phase signal and extract the geometry and size of the emitting region. Title: Spatially Resolving the Quasar Broad Emission Line Region Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...20A Altcode: The angular resolution of the Very Large Telescope Interferometer (VLTI) and the excellent sensitivity of GRAVITY have led to the first detection of spatially resolved kinematics of high velocity atomic gas near an accreting super- massive black hole, revealing rotation on sub-parsec scales in the quasar 3C 273 at a distance of 550 Mpc. The observations can be explained as the result of circular orbits in a thick disc configuration around a 300 million solar mass black hole. Within an ongoing Large Programme, this capability will be used to study the kinematics of atomic gas and its relation to hot dust in a sample of quasars and Seyfert galaxies. We will measure a new radius-luminosity relation from spatially resolved data and test the current methods used to measure black hole mass in large surveys. Title: Multiple Star Systems in the Orion Nebula Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...36G Altcode: GRAVITY observations reveal that most massive stars in the Orion Trapezium cluster live in multiple systems. Our deep, milliarcsecond-resolution interferometry fills the gap at 1-100 astronomical units (au), which is not accessible to traditional imaging and spectroscopy, but is crucial to uncovering the mystery of high-mass star formation.The new observations find a significantly higher companion fraction than earlier studies of mostly OB associations. The observed distribution of mass ratios declines steeply with mass and follows a Salpeter power-law initial mass function. The observations therefore exclude stellar mergers as the dominant formation mechanism for massive stars in Orion. Title: Images at the Highest Angular Resolution with GRAVITY: The Case of η Carinae Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...31G Altcode: The main goal of an interferometer is to probe the physics of astronomical objects at the highest possible angular resolution. The most intuitive way of doing this is by reconstructing images from the interferometric data. GRAVITY at the Very Large Telescope Interferometer (VLTI) has proven to be a fantastic instrument in this endeavour. In this article, we describe the reconstruction of the wind-wind collision cavity of the massive binary η Car with GRAVITY across two spectral lines: HeI and Brγ. Title: Probing the Discs of Herbig Ae/Be Stars at Terrestrial Orbits Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Adler, T.; Amorim, A.; Anugu, N.; Ávila, G.; Bauböck, M.; Benisty, M.; Berger, J. -P.; Bestenlehner, J. M.; Beust, H.; Blind, N.; Bonnefoy, M.; Bonnet, H.; Bourget, P.; Bouvier, J.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cantalloube, F.; Caratti O Garatti, A.; Caselli, P.; Cassaing, F.; Chapron, F.; Charnay, B.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; Davies, R.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; de Wit, W. -J.; Dexter, J.; de Zeeuw, T.; Dougados, C.; Dubus, G.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Eupen, F.; Fédou, P.; Ferreira, M. C.; Finger, G.; Förster Schreiber, N. M.; Gao, F.; García Dabó, C. E.; Garcia Lopez, R.; Garcia, P. J. V.; Gendron, É.; Genzel, R.; Gerhard, O.; Gil, J. P.; Gillessen, S.; Gonté, F.; Gordo, P.; Gratadour, D.; Greenbaum, A.; Grellmann, R.; Grözinger, U.; Guajardo, P.; Guieu, S.; Habibi, M.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haußmann, F.; Henning, T.; Hippler, S.; Hönig, S. F.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jimenez Rosales, A.; Jochum, L.; Jocou, L.; Kammerer, J.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Kishimoto, M.; Klarmann, L.; Klein, R.; Köhler, R.; Kok, Y.; Kolb, J.; Koutoulaki, M.; Kulas, M.; Labadie, L.; Lacour, S.; Lagrange, A. -M.; Lapeyrère, V.; Laun, W.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lin, C. -C.; Lippa, M.; Lutz, D.; Magnard, Y.; Maire, A. -L.; Mehrgan, L.; Mérand, A.; Millour, F.; Mollière, P.; Moulin, T.; Müller, A.; Müller, E.; Müller, F.; Netzer, H.; Neumann, U.; Nowak, M.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Peterson, B. M.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Pineda, J. E.; Plewa, P. M.; Popovic, D.; Pott, J. -U.; Prieto, A.; Pueyo, L.; Rabien, S.; Ramírez, A.; Ramos, J. R.; Rau, C.; Ray, T.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rouan, D.; Rousset, G.; Sanchez-Bermudez, J.; Schartmann, M.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Segura-Cox, D.; Shangguan, J.; Shimizu, T. T.; Spyromilio, J.; Sternberg, A.; Stock, M. R.; Straub, O.; Straubmeier, C.; Sturm, E.; Suárez Valles, M.; Tacconi, L. J.; Thi, W. -F.; Tristram, K. R. W.; Valenzuela, J. J.; van Boekel, R.; van Dishoeck, E. F.; Vermot, P.; Vincent, F.; von Fellenberg, S.; Waisberg, I.; Wang, J. J.; Wank, I.; Weber, J.; Weigelt, G.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yang, P.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2019Msngr.178...38G Altcode: More than 4000 exoplanets are known to date in systems that differ greatly from our Solar System. In particular, inner exoplanets tend to follow orbits around their parent star that are much more compact than that of Earth. These systems are also extremely diverse, covering a range of intrinsic properties. Studying the main physi- cal processes at play in the innermost regions of the protoplanetary discs is crucial to understanding how these planets form and migrate so close to their host. With GRAVITY, we focused on the study of near-infrared emission of a sample of young intermediate- mass stars, the Herbig Ae/Be stars. Title: Vertical shear mixing in stellar radiative zones Authors: Prat, V.; Guilet, J.; Vialler, M.; Müller, E. Bibcode: 2019EAS....82..167P Altcode: Jean-Paul Zahn's formalism for vertical shear mixing is used in several stellar evolution codes, but the physics of the shear instability in stellar radiative zones is still not completely understood. Over the last few years, numerical simulations have provided new constraints on the shear instability, including the effect of thermal diffusion and chemical stratification. We present here new simulations that show the effect of viscosity on the vertical turbulent transport due to the shear instability. Title: Gravitational waves from 3D core-collapse supernova models: The impact of moderate progenitor rotation Authors: Andresen, H.; Müller, E.; Janka, H. -Th; Summa, A.; Gill, K.; Zanolin, M. Bibcode: 2019MNRAS.486.2238A Altcode: 2018arXiv181007638A; 2019MNRAS.tmp..977A We present predictions for the gravitational wave (GW) emission of 3D supernova simulations performed for a 15 solar-mass progenitor with the PROMETHEUS-VERTEX code using energy-dependent, three-flavour neutrino transport. The progenitor adopted from stellar evolution calculations including magnetic fields had a fairly low specific angular momentum (jFe ≲ 1015 cm2 s-1) in the iron core (central angular velocity ΩFe,c ∼ 0.2 rad s-1), which we compared to simulations without rotation and with artificially enhanced rotation (jFe ≲ 2 × 1016 cm2 s-1; ΩFe,c ∼ 0.5 rad s-1). Our results confirm that the time-domain GW signals of SNe are stochastic, but possess deterministic components with characteristic patterns at low frequencies (≲200 Hz), caused by mass motions due to the standing accretion shock instability (SASI), and at high frequencies, associated with gravity-mode oscillations in the surface layer of the proto-neutron star (PNS). Non-radial mass motions in the post-shock layer as well as PNS convection are important triggers of GW emission, whose amplitude scales with the power of the hydrodynamic flows. There is no monotonic increase of the GW amplitude with rotation, but a clear correlation with the strength of SASI activity. Our slowly rotating model is a fainter GW emitter than the non-rotating model because of weaker SASI activity and damped convection in the post-shock layer and PNS. In contrast, the faster rotating model exhibits a powerful SASI spiral mode during its transition to explosion, producing the highest GW amplitudes with a distinctive drift of the low-frequency emission peak from ∼80-100 to ∼40-50 Hz. This migration signifies shock expansion, whereas non-exploding models are discriminated by the opposite trend. Title: Titanium hidden in dust Authors: Iyudin, A. F.; Müller, E.; Obergaulinger, M. Bibcode: 2019MNRAS.485.3288I Altcode: 2019MNRAS.tmp..424I; 2019arXiv190202249I Cassiopeia A, one of the most intriguing Galactic supernova remnants, has been a target of many observational efforts including most recent observations by Atacama Large Millimeter/submillimeter Array (ALMA), Hubble, Herschel, Spitzer, NuSTAR, INTEGRAL, and other observatories. We use recent gamma-ray lines observations of the radioactive products of Cas A supernova explosive nucleosynthesis and spectral energy densities derived for Cas A at infrared wavelengths to speculate about the possibility of radioactive {}^{44}_{}Ti being locked into large dust grains. This suggestion is also supported by the possible observation of a pre-supernova outburst about 80 yr before the actual Cas A supernova explosion in 1671 AD by Italian astronomer G. D. Cassini. The plausibility of such a scenario is discussed also with reference to recent supernovae, and to the contribution of core-collapse supernovae to the overall dust production in the Galaxy. Title: Three-dimensional mixing and light curves: constraints on the progenitor of supernova 1987A Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -Th.; Müller, E.; Ertl, T.; Woosley, S. E. Bibcode: 2019A&A...624A.116U Altcode: 2018arXiv181211083U With the same method as used previously, we investigate neutrino-driven explosions of a larger sample of blue supergiant models. The blue supergiants were evolved as single-star progenitors. The larger sample includes three new presupernova stars. The results are compared with light-curve observations of the peculiar type IIP supernova 1987A (SN 1987A). The explosions were modeled in 3D with the neutrino-hydrodynamics code PROMETHEUS-HOTB, and light-curve calculations were performed in spherical symmetry with the radiation-hydrodynamics code CRAB, starting at a stage of nearly homologous expansion. Our results confirm the basic findings of the previous work: 3D neutrino-driven explosions with SN 1987A-like energies synthesize an amount of 56Ni that is consistent with the radioactive tail of the light curve. Moreover, the models mix hydrogen inward to minimum velocities below 400 km s-1 as required by spectral observations and a 3D analysis of molecular hydrogen in SN 1987A. Hydrodynamic simulations with the new progenitor models, which possess smaller radii than the older ones, show much better agreement between calculated and observed light curves in the initial luminosity peak and during the first 20 days. A set of explosions with similar energies demonstrated that a high growth factor of Rayleigh-Taylor instabilities at the (C+O)/He composition interface combined with a weak interaction of fast Rayleigh-Taylor plumes, where the reverse shock occurs below the He/H interface, provides a sufficient condition for efficient outward mixing of 56Ni into the hydrogen envelope. This condition is realized to the required extent only in one of the older stellar models, which yielded a maximum velocity of around 3000 km s-1 for the bulk of ejected 56Ni, but failed to reproduce the helium-core mass of 6 M inferred from the absolute luminosity of the presupernova star. We conclude that none of the single-star progenitor models proposed for SN 1987A to date satisfies all constraints set by observations.

Data of the presupernova models for blue supergiants, the angle-averaged profiles of the 3D explosion models, and the corresponding bolometric light curves are available in electronic form at the CDS via anonymous ftp http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A116 Title: VizieR Online Data Catalog: Constraints on the progenitor of SN 1987A (Utrobin+, 2019) Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -T.; Mueller, E.; Ertl, T.; Woosley, S. E. Bibcode: 2019yCat..36240116U Altcode: 7 presupernova models for blue supergiants B15, W16, W18, W18r, W18x, W20, and N20 were used as initial data for 3D simulations of neutrino-driven explosions and the corresponding hydrodynamic models B15-2, W16-3, W18, W18r-2, W18x-2, W20, and N20-P with SN 1987A-like explosion energies were calculated. 3D models B15-2, W16-3, W18, W18r-2, W18x-2, W20, and N20-P were mapped to spherically symmetric configurations at a stage of almost homologous expansion: 61218.22s, 88487.02s, 55204.19s, 89773.06s, 89134.01s, 61243.24s, and 56861.61s, respectively. These 1D configurations were used as initial data for simulations of bolometric light curves.

(28 data files). Title: ePESSTO Transient Classification Report for 2018-12-03 Authors: Pursiainen; M; Castro; N; Gutierrez; P, C.; Muller; T; Yaron, O. Bibcode: 2018TNSCR2051....1P Altcode: No abstract at ADS Title: GRAVITY chromatic imaging of η Car's core. Milliarcsecond resolution imaging of the wind-wind collision zone (Brγ, He I) Authors: GRAVITY Collaboration; Sanchez-Bermudez, J.; Weigelt, G.; Bestenlehner, J. M.; Kervella, P.; Brandner, W.; Henning, Th.; Müller, A.; Perrin, G.; Pott, J. -U.; Schöller, M.; van Boekel, R.; Abuter, R.; Accardo, M.; Amorim, A.; Anugu, N.; Ávila, G.; Benisty, M.; Berger, J. P.; Blind, N.; Bonnet, H.; Bourget, P.; Brast, R.; Buron, A.; Cantalloube, F.; Caratti O Garatti, A.; Cassaing, F.; Chapron, F.; Choquet, E.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; de Wit, W.; de Zeeuw, T.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; Dexter, J.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Fédou, P.; Garcia, P. J. V.; Garcia Dabo, C. E.; Garcia Lopez, R.; Gao, F.; Gendron, E.; Genzel, R.; Gillessen, S.; Haubois, X.; Haug, M.; Haussmann, F.; Hippler, S.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Jochum, L.; Jocou, L.; Karl, M.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kiekebusch, M.; Klein, R.; Kolb, J.; Kulas, M.; Lacour, S.; Lapeyrère, V.; Lazareff, B.; Le Bouquin, J. -B.; Léna, P.; Lenzen, R.; Lévêque, S.; Lippa, M.; Magnard, Y.; Mehrgan, L.; Mellein, M.; Mérand, A.; Moreno-Ventas, J.; Moulin, T.; Müller, E.; Müller, F.; Neumann, U.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Petrucci, P. -O.; Pflüger, A.; Pfuhl, O.; Duc, T. P.; Plewa, P. M.; Popovic, D.; Rabien, S.; Ramirez, A.; Ramos, J.; Rau, C.; Riquelme, M.; Rodríguez-Coira, G.; Rohloff, R. -R.; Rosales, A.; Rousset, G.; Scheithauer, S.; Schuhler, N.; Spyromilio, J.; Straub, O.; Straubmeier, C.; Sturm, E.; Suarez, M.; Tristram, K. R. W.; Ventura, N.; Vincent, F.; Waisberg, I.; Wank, I.; Widmann, F.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2018A&A...618A.125G Altcode: 2018arXiv180802141G Context. η Car is one of the most intriguing luminous blue variables in the Galaxy. Observations and models of the X-ray, ultraviolet, optical, and infrared emission suggest a central binary in a highly eccentric orbit with a 5.54 yr period residing in its core. 2D and 3D radiative transfer and hydrodynamic simulations predict a primary with a dense and slow stellar wind that interacts with the faster and lower density wind of the secondary. The wind-wind collision scenario suggests that the secondary's wind penetrates the primary's wind creating a low-density cavity in it, with dense walls where the two winds interact. However, the morphology of the cavity and its physical properties are not yet fully constrained.
Aims: We aim to trace the inner ∼5-50 au structure of η Car's wind-wind interaction, as seen through Brγ and, for the first time, through the He I 2s-2p line.
Methods: We have used spectro-interferometric observations with the K-band beam-combiner GRAVITY at the VLTI. The analyses of the data include (i) parametrical model-fitting to the interferometric observables, (ii) a CMFGEN model of the source's spectrum, and (iii) interferometric image reconstruction.
Results: Our geometrical modeling of the continuum data allows us to estimate its FWHM angular size close to 2 mas and an elongation ratio ɛ = 1.06 ± 0.05 over a PA = 130° ± 20°. Our CMFGEN modeling of the spectrum helped us to confirm that the role of the secondary should be taken into account to properly reproduce the observed Brγ and He I lines. Chromatic images across the Brγ line reveal a southeast arc-like feature, possibly associated to the hot post-shocked winds flowing along the cavity wall. The images of the He I 2s-2p line served to constrain the 20 mas (∼50 au) structure of the line-emitting region. The observed morphology of He I suggests that the secondary is responsible for the ionized material that produces the line profile. Both the Brγ and the He I 2s-2p maps are consistent with previous hydrodynamical models of the colliding wind scenario. Future dedicated simulations together with an extensive interferometric campaign are necessary to refine our constraints on the wind and stellar parameters of the binary, which finally will help us predict the evolutionary path of η Car. Title: Papaloizou-Pringle instability suppression by the magnetorotational instability in relativistic accretion discs Authors: Bugli, M.; Guilet, J.; Müller, E.; Del Zanna, L.; Bucciantini, N.; Montero, P. J. Bibcode: 2018MNRAS.475..108B Altcode: 2017arXiv170701860B Geometrically thick tori with constant specific angular momentum have been widely used in the last decades to construct numerical models of accretion flows on to black holes. Such discs are prone to a global non-axisymmetric hydrodynamic instability, known as Papaloizou-Pringle instability (PPI), which can redistribute angular momentum and also lead to an emission of gravitational waves. It is, however, not clear yet how the development of the PPI is affected by the presence of a magnetic field and by the concurrent development of the magnetorotational instability (MRI). We present a numerical analysis using three-dimensional GRMHD simulations of the interplay between the PPI and the MRI considering, for the first time, an analytical magnetized equilibrium solution as initial condition. In the purely hydrodynamic case, the PPI selects as expected the large-scale m = 1 azimuthal mode as the fastest growing and non-linearly dominant mode. However, when the torus is threaded by a weak toroidal magnetic field, the development of the MRI leads to the suppression of large-scale modes and redistributes power across smaller scales. If the system starts with a significantly excited m = 1 mode, the PPI can be dominant in a transient phase, before being ultimately quenched by the MRI. Such dynamics may well be important in compact star mergers and tidal disruption events. Title: Emission line models for the lowest mass core-collapse supernovae - I. Case study of a 9 M one-dimensional neutrino-driven explosion Authors: Jerkstrand, A.; Ertl, T.; Janka, H. -T.; Müller, E.; Sukhbold, T.; Woosley, S. E. Bibcode: 2018MNRAS.475..277J Altcode: 2017arXiv171004508J A large fraction of core-collapse supernovae (CCSNe), 30-50 per cent, are expected to originate from the low-mass end of progenitors with MZAMS = 8-12 M. However, degeneracy effects make stellar evolution modelling of such stars challenging, and few predictions for their supernova light curves and spectra have been presented. Here, we calculate synthetic nebular spectra of a 9 M Fe CCSN model exploded with the neutrino mechanism. The model predicts emission lines with FWHM ∼ 1000 km s-1, including signatures from each deep layer in the metal core. We compare this model to the observations of the three subluminous IIP SNe with published nebular spectra; SN 1997D, SN 2005cs and SN 2008bk. The predictions of both line profiles and luminosities are in good agreement with SN 1997D and SN 2008bk. The close fit of a model with no tuning parameters provides strong evidence for an association of these objects with low-mass Fe CCSNe. For SN 2005cs, the interpretation is less clear, as the observational coverage ended before key diagnostic lines from the core had emerged. We perform a parametrized study of the amount of explosively made stable nickel, and find that none of these three SNe show the high 58Ni/56Ni ratio predicted by current models of electron capture SNe (ECSNe) and ECSN-like explosions. Combined with clear detection of lines from O and He shell material, these SNe rather originate from Fe core progenitors. We argue that the outcome of self-consistent explosion simulations of low-mass stars, which gives fits to many key observables, strongly suggests that the class of subluminous Type IIP SNe is the observational counterpart of the lowest mass CCSNe. Title: Isolated massive star formation . Myth or reality? Authors: Gouliermis, D. A.; Stephens, I. W.; Looney, L. W.; Gruendl, R. A.; Chu, Y. -H.; Weisz, D. R.; Seale, J. P.; Chen, C. -H. R.; Wong, T.; Hughes, A.; Pineda, J. L.; Ott, J.; Muller, E. Bibcode: 2018MmSAI..89...57G Altcode: High-mass stars apparently formed in the field challenge the paradigm of clustered star formation. To understand the conditions that favor isolated massive star formation, we employed the Hubble Space Telescope to observe the seven most isolated massive YSOs in the LMC. Our investigation shows that while they are quite remote from any star-forming region, these YSOs are not isolated at all. HST revealed a plethora of Pre-Main-Sequence stars, forming compact clusters around the YSOs, and sparsely distributed across the observed regions. Contrary to previous studies, these observations suggest that high-mass stars may not be able to form in clusters smaller than 100 M_⊙, and that the lack of isolation is at odds with random sampling of the stellar IMF. Title: Magneto-elastic oscillations modulating the emission of magnetars Authors: Gabler, M.; Cerdá-Durán, P.; Mate, A.; Stergioulas, N.; Font, J. A.; Müller, E. Bibcode: 2017AN....338.1105G Altcode: 2017arXiv170906806G Magneto-elastic oscillations of neutron stars are believed to explain the observed quasi-periodic oscillations (QPOs) in the decaying tail of the giant flares of highly magnetized neutron stars (magnetars). Strong efforts by theoretical modeling from different groups have increased our understanding of this phenomenon significantly. Here we discuss some constraints on the matter in neutron stars that arise if the interpretation of the observations in terms of superfluid magneto-elastic oscillations is correct. To explain the observed modulation of the light curve of the giant flare, we describe a model that allows the QPOs to couple to the stellar exterior through the magnetic field. In this magnetosphere, the shaking magnetic field induces currents that provide scattering targets for resonant cyclotron scattering of photons, which is calculated with a Monte Carlo approach and coupled to a code that calculates the momentum distribution of the charge carriers as a one-dimensional accelerator problem. We show first results of a simplified, but self-consistent momentum distribution, that is a water-bag distribution, and the corresponding spectra. Title: The wind and the magnetospheric accretion onto the T Tauri star S Coronae Australis at sub-au resolution Authors: GRAVITY Collaboration; Garcia Lopez, R.; Perraut, K.; Caratti O Garatti, A.; Lazareff, B.; Sanchez-Bermudez, J.; Benisty, M.; Dougados, C.; Labadie, L.; Brandner, W.; Garcia, P. J. V.; Henning, Th.; Ray, T. P.; Abuter, R.; Amorim, A.; Anugu, N.; Berger, J. P.; Bonnet, H.; Buron, A.; Caselli, P.; Clénet, Y.; Coudé Du Foresto, V.; de Wit, W.; Deen, C.; Delplancke-Ströbele, F.; Dexter, J.; Eckart, A.; Eisenhauer, F.; Garcia Dabo, C. E.; Gendron, E.; Genzel, R.; Gillessen, S.; Haubois, X.; Haug, M.; Haussmann, F.; Hippler, S.; Hubert, Z.; Hummel, C. A.; Horrobin, M.; Jocou, L.; Kellner, S.; Kervella, P.; Kulas, M.; Kolb, J.; Lacour, S.; Le Bouquin, J. -B.; Léna, P.; Lippa, M.; Mérand, A.; Müller, E.; Ott, T.; Panduro, J.; Paumard, T.; Perrin, G.; Pfuhl, O.; Ramirez, A.; Rau, C.; Rohloff, R. -R.; Rousset, G.; Scheithauer, S.; Schöller, M.; Straubmeier, C.; Sturm, E.; Thi, W. F.; van Dishoeck, E.; Vincent, F.; Waisberg, I.; Wank, I.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Woillez, J.; Yazici, S.; Zins, G. Bibcode: 2017A&A...608A..78G Altcode: 2017arXiv170901348G
Aims: To investigate the inner regions of protoplanetary discs, we performed near-infrared interferometric observations of the classical T Tauri binary system S CrA.
Methods: We present the first VLTI-GRAVITY high spectral resolution (R ~ 4000) observations of a classical T Tauri binary, S CrA (composed of S CrA N and S CrA S and separated by ~1.̋4), combining the four 8m telescopes in dual-field mode.
Results: Our observations in the near-infrared K-band continuum reveal a disc around each binary component, with similar half-flux radii of about 0.1 au at d ~ 130 pc, inclinations (i = 28 ± 3° and i = 22 ± 6°), and position angles (PA = 0°± 6° and PA = -2°± 12°), suggesting that they formed from the fragmentation of a common disc. The S CrA N spectrum shows bright He I and Brγ line emission exhibiting inverse P Cygni profiles, typically associated with infalling gas. The continuum-compensated Brγ line visibilities of S CrA N show the presence of a compact Brγ emitting region whose radius is about ~0.06 au, which is twice as big as the truncation radius. This component is mostly tracing a wind. Moreover, a slight radius change between the blue- and red-shifted Brγ line components is marginally detected.
Conclusions: The presence of an inverse P Cygni profile in the He I and Brγ lines, along with the tentative detection of a slightly larger size of the blue-shifted Brγ line component, hint at the simultaneous presence of a wind and magnetospheric accretion in S CrA N. Title: Light-curve Analysis of Ordinary Type IIP Supernovae Based on Neutrino-driven Explosion Simulations in Three Dimensions Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -Th.; Müller, E. Bibcode: 2017ApJ...846...37U Altcode: 2017arXiv170403800U Type II-plateau supernovae (SNe IIP) are the most numerous subclass of core-collapse SNe originating from massive stars. In the framework of the neutrino-driven explosion mechanism, we study the properties of the SN outburst for a red supergiant progenitor model and compare the corresponding light curves with observations of the ordinary Type IIP SN 1999em. Three-dimensional (3D) simulations of (parametrically triggered) neutrino-driven explosions are performed with the (explicit, finite-volume, Eulerian, multifluid hydrodynamics) code Prometheus, using a presupernova model of a 15 M star as initial data. On approaching homologous expansion, the hydrodynamic and composition variables of the 3D models are mapped to a spherically symmetric configuration, and the simulations are continued with the (implicit, Lagrangian, radiation hydrodynamics) code Crab to follow the evolution of the blast wave during the SN outburst. Our 3D neutrino-driven explosion model with an explosion energy of about 0.5× {10}51 erg produces 56Ni in rough agreement with the amount deduced from fitting the radioactively powered light-curve tail of SN 1999em. The considered presupernova model, 3D explosion simulations, and light-curve calculations can explain the basic observational features of SN 1999em, except for those connected to the presupernova structure of the outer stellar layers. Our 3D simulations show that the distribution of 56Ni-rich matter in velocity space is asymmetric with a strong dipole component that is consistent with the observations of SN 1999em. The monotonic decline in luminosity from the plateau to the radioactive tail in ordinary SNe IIP is a manifestation of the intense turbulent mixing at the He/H composition interface. Title: VizieR Online Data Catalog: AzTEC/ASTE survey at 1.1mm toward the SMC (Takekoshi+, 2017) Authors: Takekoshi, T.; Minamidani, T.; Komugi, S.; Kohno, K.; Tosaki, T.; Sorai, K.; Muller, E.; Mizuno, N.; Kawamura, A.; Onishi, T.; Fukui, Y.; Ezawa, H.; Oshima, T.; Scott, K. S.; Austermann, J. E.; Matsuo, H.; Aretxaga, I.; Hughes, D. H.; Kawabe, R.; Wilson, G. W.; Yun, M. S. Bibcode: 2017yCat..18350055T Altcode: Continuum observations at 1.1mm toward the SMC were conducted with the AzTEC instrument installed on the ASTE telescope in the Atacama desert, Chile. The angular resolution is 28" at FWHM. The observations covered a total of a 4.5deg2 field of the SMC by connecting four patches of scans that are denominated as southwest (SW), northeast (NE), Wing, and N88, as shown in Figure 1. Observations were performed from 2008 October 7 to December 26.

(5 data files). Title: Submilliarcsecond Optical Interferometry of the High-mass X-Ray Binary BP Cru with VLTI/GRAVITY Authors: Waisberg, I.; Dexter, J.; Pfuhl, O.; Abuter, R.; Amorim, A.; Anugu, N.; Berger, J. P.; Blind, N.; Bonnet, H.; Brandner, W.; Buron, A.; Clénet, Y.; de Wit, W.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Duvert, G.; Eckart, A.; Eisenhauer, F.; Fédou, P.; Finger, G.; Garcia, P.; Garcia Lopez, R.; Gendron, E.; Genzel, R.; Gillessen, S.; Haubois, X.; Haug, M.; Haussmann, F.; Henning, Th.; Hippler, S.; Horrobin, M.; Hubert, Z.; Jochum, L.; Jocou, L.; Kervella, P.; Kok, Y.; Kulas, M.; Lacour, S.; Lapeyrère, V.; Le Bouquin, J. -B.; Léna, P.; Lippa, M.; Mérand, A.; Müller, E.; Ott, T.; Pallanca, L.; Panduro, J.; Paumard, T.; Perraut, K.; Perrin, G.; Rabien, S.; Ramírez, A.; Ramos, J.; Rau, C.; Rohloff, R. -R.; Rousset, G.; Sanchez-Bermudez, J.; Scheithauer, S.; Schöller, M.; Straubmeier, C.; Sturm, E.; Vincent, F.; Wank, I.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Yazici, S.; GRAVITY Collaboration Bibcode: 2017ApJ...844...72W Altcode: 2017arXiv170502351G We observe the high-mass X-ray binary (HMXB) BP Cru using interferometry in the near-infrared K band with VLTI/GRAVITY. Continuum visibilities are at most partially resolved, consistent with the predicted size of the hypergiant. Differential visibility amplitude ({{Δ }}| V| ∼ 5 % ) and phase ({{Δ }}φ ∼ 2^\circ ) signatures are observed across the He I 2.059 μ {{m}} and Brγ lines, the latter seen strongly in emission, unusual for the donor star’s spectral type. For a baseline B∼ 100 m, the differential phase rms ∼ 0\buildrel{\circ}\over{.} 2 corresponds to an astrometric precision of ∼ 2 μ {as}. We generalize expressions for image centroid displacements and variances in the marginally resolved limit of interferometry to spectrally resolved data, and use them to derive model-independent properties of the emission such as its asymmetry, extension, and strong wavelength dependence. We propose geometric models based on an extended and distorted wind and/or a high-density gas stream, which has long been predicted to be present in this system. The observations show that optical interferometry is now able to resolve HMXBs at the spatial scale where accretion takes place, and therefore to probe the effects of the gravitational and radiation fields of the compact object on its environment. Title: Observing the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping Authors: White, S. M.; Iwai, K.; Phillips, N. M.; Hills, R. E.; Hirota, A.; Yagoubov, P.; Siringo, G.; Shimojo, M.; Bastian, T. S.; Hales, A. S.; Sawada, T.; Asayama, S.; Sugimoto, M.; Marson, R. G.; Kawasaki, W.; Muller, E.; Nakazato, T.; Sugimoto, K.; Brajša, R.; Skokić, I.; Bárta, M.; Kim, S.; Remijan, A. J.; de Gregorio, I.; Corder, S. A.; Hudson, H. S.; Loukitcheva, M.; Chen, B.; De Pontieu, B.; Fleishmann, G. D.; Gary, D. E.; Kobelski, A.; Wedemeyer, S.; Yan, Y. Bibcode: 2017SoPh..292...88W Altcode: 2017arXiv170504766W The Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12 m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that uses the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions, we derive quiet-Sun values at disk center of 7300 K at λ =3 mm and 5900 K at λ =1.3 mm. These values have statistical uncertainties of about 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of about 25, the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range. Active regions and plages are among the hotter features, while a large sunspot umbra shows up as a depression, and filament channels are relatively cool. Prominences above the solar limb are a common feature of the single-dish images. Title: Gravitational wave signals from 3D neutrino hydrodynamics simulations of core-collapse supernovae Authors: Andresen, H.; Müller, B.; Müller, E.; Janka, H. -Th. Bibcode: 2017MNRAS.468.2032A Altcode: 2016arXiv160705199A We present gravitational wave (GW) signal predictions from four 3D multigroup neutrino hydrodynamics simulations of core-collapse supernovae of progenitors with 11.2, 20 and 27 M. GW emission in the pre-explosion phase strongly depends on whether the post-shock flow is dominated by the standing accretion shock instability (SASI) or convection and differs considerably from 2D models. SASI activity produces a strong signal component below 250 Hz through asymmetric mass motions in the gain layer and a non-resonant coupling to the proto-neutron star (PNS). Both convection- and SASI-dominated models show GW emission above 250 Hz, but with considerably lower amplitudes than in 2D. This is due to a different excitation mechanism for high-frequency l = 2 motions in the PNS surface, which are predominantly excited by PNS convection in 3D. Resonant excitation of high-frequency surface g modes in 3D by mass motions in the gain layer is suppressed compared to 2D because of smaller downflow velocities and a lack of high-frequency variability in the downflows. In the exploding 20 M model, shock revival results in enhanced low-frequency emission due to a change of the preferred scale of the convective eddies in the PNS convection zone. Estimates of the expected excess power in two frequency bands suggest that second-generation detectors will only be able to detect very nearby events, but that third-generation detectors could distinguish SASI- and convection-dominated models at distances of ∼ 10 kpc. Title: First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer Authors: GRAVITY Collaboration; Abuter, R.; Accardo, M.; Amorim, A.; Anugu, N.; Ávila, G.; Azouaoui, N.; Benisty, M.; Berger, J. P.; Blind, N.; Bonnet, H.; Bourget, P.; Brandner, W.; Brast, R.; Buron, A.; Burtscher, L.; Cassaing, F.; Chapron, F.; Choquet, É.; Clénet, Y.; Collin, C.; Coudé Du Foresto, V.; de Wit, W.; de Zeeuw, P. T.; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Derie, F.; Dexter, J.; Duvert, G.; Ebert, M.; Eckart, A.; Eisenhauer, F.; Esselborn, M.; Fédou, P.; Finger, G.; Garcia, P.; Garcia Dabo, C. E.; Garcia Lopez, R.; Gendron, E.; Genzel, R.; Gillessen, S.; Gonte, F.; Gordo, P.; Grould, M.; Grözinger, U.; Guieu, S.; Haguenauer, P.; Hans, O.; Haubois, X.; Haug, M.; Haussmann, F.; Henning, Th.; Hippler, S.; Horrobin, M.; Huber, A.; Hubert, Z.; Hubin, N.; Hummel, C. A.; Jakob, G.; Janssen, A.; Jochum, L.; Jocou, L.; Kaufer, A.; Kellner, S.; Kendrew, S.; Kern, L.; Kervella, P.; Kiekebusch, M.; Klein, R.; Kok, Y.; Kolb, J.; Kulas, M.; Lacour, S.; Lapeyrère, V.; Lazareff, B.; Le Bouquin, J. -B.; Lèna, P.; Lenzen, R.; Lévêque, S.; Lippa, M.; Magnard, Y.; Mehrgan, L.; Mellein, M.; Mérand, A.; Moreno-Ventas, J.; Moulin, T.; Müller, E.; Müller, F.; Neumann, U.; Oberti, S.; Ott, T.; Pallanca, L.; Panduro, J.; Pasquini, L.; Paumard, T.; Percheron, I.; Perraut, K.; Perrin, G.; Pflüger, A.; Pfuhl, O.; Phan Duc, T.; Plewa, P. M.; Popovic, D.; Rabien, S.; Ramírez, A.; Ramos, J.; Rau, C.; Riquelme, M.; Rohloff, R. -R.; Rousset, G.; Sanchez-Bermudez, J.; Scheithauer, S.; Schöller, M.; Schuhler, N.; Spyromilio, J.; Straubmeier, C.; Sturm, E.; Suarez, M.; Tristram, K. R. W.; Ventura, N.; Vincent, F.; Waisberg, I.; Wank, I.; Weber, J.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Wolff, B.; Yazici, S.; Ziegler, D.; Zins, G. Bibcode: 2017A&A...602A..94G Altcode: 2017arXiv170502345G GRAVITY is a new instrument to coherently combine the light of the European Southern Observatory Very Large Telescope Interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m2. The instrument comprises fiber fed integrated optics beam combination, high resolution spectroscopy, built-in beam analysis and control, near-infrared wavefront sensing, phase-tracking, dual-beam operation, and laser metrology. GRAVITY opens up to optical/infrared interferometry the techniques of phase referenced imaging and narrow angle astrometry, in many aspects following the concepts of radio interferometry. This article gives an overview of GRAVITY and reports on the performance and the first astronomical observations during commissioning in 2015/16. We demonstrate phase-tracking on stars as faint as mK ≈ 10 mag, phase-referenced interferometry of objects fainter than mK ≈ 15 mag with a limiting magnitude of mK ≈ 17 mag, minute long coherent integrations, a visibility accuracy of better than 0.25%, and spectro-differential phase and closure phase accuracy better than 0.5°, corresponding to a differential astrometric precision of better than ten microarcseconds (μas). The dual-beam astrometry, measuring the phase difference of two objects with laser metrology, is still under commissioning. First observations show residuals as low as 50 μas when following objects over several months. We illustrate the instrument performance with the observations of archetypical objects for the different instrument modes. Examples include the Galactic center supermassive black hole and its fast orbiting star S2 for phase referenced dual-beam observations and infrared wavefront sensing, the high mass X-ray binary BP Cru and the active galactic nucleus of PDS 456 for a few μas spectro-differential astrometry, the T Tauri star S CrA for a spectro-differential visibility analysis, ξ Tel and 24 Cap for high accuracy visibility observations, and η Car for interferometric imaging with GRAVITY. Title: Accretion-ejection morphology of the microquasar SS 433 resolved at sub-au scale Authors: GRAVITY Collaboration; Petrucci, P. -O.; Waisberg, I.; Le Bouquin, J. -B.; Dexter, J.; Dubus, G.; Perraut, K.; Kervella, P.; Abuter, R.; Amorim, A.; Anugu, N.; Berger, J. P.; Blind, N.; Bonnet, H.; Brandner, W.; Buron, A.; Choquet, É.; Clénet, Y.; de Wit, W.; Deen, C.; Eckart, A.; Eisenhauer, F.; Finger, G.; Garcia, P.; Garcia Lopez, R.; Gendron, E.; Genzel, R.; Gillessen, S.; Gonte, F.; Haubois, X.; Haug, M.; Haussmann, F.; Henning, Th.; Hippler, S.; Horrobin, M.; Hubert, Z.; Jochum, L.; Jocou, L.; Kok, Y.; Kolb, J.; Kulas, M.; Lacour, S.; Lazareff, B.; Lèna, P.; Lippa, M.; Mérand, A.; Müller, E.; Ott, T.; Panduro, J.; Paumard, T.; Perrin, G.; Pfuhl, O.; Ramos, J.; Rau, C.; Rohloff, R. -R.; Rousset, G.; Sanchez-Bermudez, J.; Scheithauer, S.; Schöller, M.; Straubmeier, C.; Sturm, E.; Vincent, F.; Wank, I.; Wieprecht, E.; Wiest, M.; Wiezorrek, E.; Wittkowski, M.; Woillez, J.; Yazici, S.; Zins, G. Bibcode: 2017A&A...602L..11G Altcode: 2017arXiv170502359G We present the first optical observation of the microquasar SS 433 at sub-milliarcsecond (mas) scale obtained with the GRAVITY instrument on the Very Large Telescope interferometer (VLTI). The 3.5-h exposure reveals a rich K-band spectrum dominated by hydrogen Brγand He I lines, as well as (red-shifted)emission lines coming from the jets. The K-band-continuum-emitting region is dominated by a marginally resolved point source (<1 mas) embedded inside a diffuse background accounting for 10% of the total flux. The jet line positions agree well with the ones expected from the jet kinematic model, an interpretation also supported by the consistent sign (i.e., negative/positive for the receding/approaching jet component) of the phase shifts observed in the lines. The significant visibility drop across the jet lines, together with the small and nearly identical phases for all baselines, point toward a jet that is offset by less than 0.5 mas from the continuum source and resolved in the direction of propagation, with a typical size of 2 mas. The jet position angle of ~80° is consistent with the expected one at the observation date. Jet emission so close to the central binary system would suggest that line locking, if relevant to explain the amplitude and stability of the 0.26c jet velocity, operates on elements heavier than hydrogen. The Brγprofile is broad and double peaked. It is better resolved than the continuum and the change of the phase signal sign across the line on all baselines suggests an East-West-oriented geometry similar to the jet direction and supporting a (polar) disk wind origin.

Based on observations made with VLTI/Gravity instrument. Title: VizieR Online Data Catalog: YSO candidates in the Magellanic Bridge (Chen+, 2014) Authors: Chen, C. -H. R.; Indebetouw, R.; Muller, E.; Kawamura, A.; Gordon, K. D.; Sewilo, M.; Whitney, B. A.; Fukui, Y.; Madden, S. C.; Meade, M. R.; Meixner, M.; Oliveira, J. M.; Robitaille, T. P.; Seale, J. P.; Shiao, B.; van Loon, J. Th. Bibcode: 2017yCat..17850162C Altcode: The Spitzer observations of the Bridge were obtained as part of the Legacy Program "Surveying the Agents of Galaxy Evolution in the Tidally-Stripped, Low-Metallicity Small Magellanic Cloud" (SAGE-SMC; Gordon et al. 2011AJ....142..102G). These observations included images taken at 3.6, 4.5, 5.8, and 8.0 um bands with the InfraRed Array Camera (IRAC) and at 24, 70, and 160 um bands with the Multiband Imaging Photometer for Spitzer (MIPS). The details of data processing are given in Gordon et al. (2011AJ....142..102G). To construct multi-wavelength SEDs for sources in the Spitzer catalog, we have expanded it by adding photometry from optical and NIR surveys covering the Bridge, i.e., BRI photometry from the Super COSMOS Sky Surveys (SSS; Hambly et al. 2001MNRAS.326.1279H) and JHKs photometry from the Two Micron All Sky Survey (2MASS; Skrutskie et al. 2006AJ....131.1163S, Cat. VII/233).

(5 data files). Title: SEDIGISM: Structure, excitation, and dynamics of the inner Galactic interstellar medium Authors: Schuller, F.; Csengeri, T.; Urquhart, J. S.; Duarte-Cabral, A.; Barnes, P. J.; Giannetti, A.; Hernandez, A. K.; Leurini, S.; Mattern, M.; Medina, S. -N. X.; Agurto, C.; Azagra, F.; Anderson, L. D.; Beltrán, M. T.; Beuther, H.; Bontemps, S.; Bronfman, L.; Dobbs, C. L.; Dumke, M.; Finger, R.; Ginsburg, A.; Gonzalez, E.; Henning, T.; Kauffmann, J.; Mac-Auliffe, F.; Menten, K. M.; Montenegro-Montes, F. M.; Moore, T. J. T.; Muller, E.; Parra, R.; Perez-Beaupuits, J. -P.; Pettitt, A.; Russeil, D.; Sánchez-Monge, Á.; Schilke, P.; Schisano, E.; Suri, S.; Testi, L.; Torstensson, K.; Venegas, P.; Wang, K.; Wienen, M.; Wyrowski, F.; Zavagno, A. Bibcode: 2017A&A...601A.124S Altcode: 2017arXiv170104712S Context. The origin and life-cycle of molecular clouds are still poorly constrained, despite their importance for understanding the evolution of the interstellar medium. Many large-scale surveys of the Galactic plane have been conducted recently, allowing for rapid progress in this field. Nevertheless, a sub-arcminute resolution global view of the large-scale distribution of molecular gas, from the diffuse medium to dense clouds and clumps, and of their relationshipto the spiral structure, is still missing.
Aims: We have carried out a systematic, homogeneous, spectroscopic survey of the inner Galactic plane, in order to complement the many continuum Galactic surveys available with crucial distance and gas-kinematic information. Our aim is to combine this data set with recent infrared to sub-millimetre surveys at similar angular resolutions.
Methods: The SEDIGISM survey covers 78 deg2 of the inner Galaxy (-60°≤ℓ≤ 18°, |b|≤ 0.5°) in the J = 2-1 rotational transition of 13CO. This isotopologue of CO is less abundant than 12CO by factors up to 100. Therefore, its emission has low to moderate optical depths, and higher critical density, making it an ideal tracer of the cold, dense interstellar medium. The data have been observed with the SHFI single-pixel instrument at APEX. The observational setup covers the 13CO(2-1) and C18O(2-1) lines, plus several transitions from other molecules.
Results: The observations have been completed. Data reduction is in progress, and the final data products will be made available in the near future. Here we give a detailed description of the survey and the dedicated data reduction pipeline. To illustrate the scientific potential of this survey, preliminary results based on a science demonstration field covering -20°≤ℓ ≤ -18.5° are presented. Analysis of the 13CO(2-1) data in this field reveals compact clumps, diffuse clouds, and filamentary structures at a range of heliocentric distances. By combining our data with data in the (1-0) transition of CO isotopologues from the ThrUMMS survey, we are able to compute a 3D realization of the excitation temperature and optical depth in the interstellar medium. Ultimately, this survey will provide a detailed, global view of the inner Galactic interstellar medium at an unprecedented angular resolution of 30''.

This publication is based on data acquired with the Atacama Pathfinder EXperiment (APEX) under programmes 092.F-9315(A) and 193.C-0584(A). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.Full Table 5 and Table A.1 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A124 Title: VizieR Online Data Catalog: Clouds in SEDIGISM science demonstration field (Schuller+, 2017) Authors: Schuller, F.; Csengeri, T.; Urquhart, J. S.; Duarte-Cabral, A.; Barnes, P. J.; Giannetti, A.; Hernandez, A. K.; Leurini, S.; Mattern, M.; Medina, S. -N. X.; Agurto, C.; Azagra, F.; Anderson, L. D.; Beltran, M. T.; Beuther, H.; Bontemps, S.; Bronfman, L.; Dobbs, C. L.; Dumke, M.; Finger, R.; Ginsburg, A.; Gonzalez, E.; Henning, T.; Kauffmann, J.; Mac-Auliffe, F.; Menten, K. M.; Montenegro-Montes, F. M.; Moore, T. J. T.; Muller, E.; Parra, R.; Perez-Beaupuits, J. -P.; Pettitt, A.; Russeil, D.; Sanchez-Monge, A.; Schilke, P.; Schisano, E.; Suri, S.; Testi, L.; Torstensson, K.; Venegas, P.; Wang, K.; Wienen, M.; Wyrowski, F.; Zavagno, A. Bibcode: 2017yCat..36010124S Altcode: Properties of ATLASGAL compact sources located in the SEDIGISM science demonstration field, and properties of molecular clouds and complexes extracted from the 13CO(2-1) data covering the same field. The extraction of clouds was performed using the SCIMES algorithm (Colombo et al., 2015MNRAS.454.2067C).

(2 data files). Title: The ALMA Science Archive Authors: Stoehr, F.; Manning, A.; Moins, C.; Jenkins, D.; Lacy, M.; Leon, S.; Muller, E.; Nakanishi, K.; Matthews, B.; Gaudet, S.; Murphy, E.; Ashitagawa, K.; Kawamura, A. Bibcode: 2017Msngr.167....2S Altcode: Science archives help to maximise the scientific return of astronomical facilities. After placing science archives into a slightly larger context, we describe the current status and capabilities of the ALMA Science Archive. We present the design principles and technology employed for three main contexts: query; result set display; and data download. A summary of the ALMA data flow is also presented as are access statistics to date. Title: VizieR Online Data Catalog: Galactic CHaMP. III. 12CO dense clump properties (Barnes+, Authors: Barnes, P. J.; Hernandez, A. K.; O'Dougherty, S. N.; Schap, W. J., III; Muller, E. Bibcode: 2017yCat..18310067B Altcode: In Phase II of the Mopra observing for the Census of High- and Medium-mass Protostars (CHaMP) project during 2009-12, we tuned the receiver to a central frequency of 111.3GHz and set up the Mopra Spectrometer (MOPS) digital filterbank to map all the CHaMP clumps in a second set of spectral lines at frequencies of 107-115GHz. This new set of transitions most notably includes the J=1->0 lines for the triad of CO-isotopologue species, 12CO, 13CO, and C18O.

(3 data files). Title: Supernovae from the 8-10 M_⊙ range: the first spectral models for the emission-line phase Authors: Jerkstrand, A.; Ertl, T.; Janka, H. -T.; Müller, E. Bibcode: 2017MmSAI..88..278J Altcode: Stars in the MZAMS=8-10 M_⊙ range are expected to account for about 1/3 of all core-collapse supernovae (SNe). Here we describe calculations of the first spectral models in the nebular phase (t>200d) for such SNe, and the diagnostic potential of these. Comparison of a 9 M_⊙ SN model with SN 1997D suggests that the observational class of subluminous Type IIP SNe is linked to the low-mass end of progenitors. We discuss potential diagnostics of electron capture supernovae from 58Ni lines. Title: Magnetorotational Instability in Core-collapse Supernovae Authors: Rembiasz, T.; Obergaulinger, M.; Guilet, J.; Cerdá-Durán, P.; Aloy, M. A.; Müller, E. Bibcode: 2017AcPPS..10..361R Altcode: 2017arXiv170700983R We discuss the relevance of the magnetorotational instability (MRI) in core-collapse supernovae (CCSNe). Our recent numerical studies show that in CCSNe, the MRI is terminated by parasitic instabilities of the Kelvin-Helmholtz type. To determine whether the MRI can amplify initially weak magnetic fields to dynamically relevant strengths in CCSNe, we performed three-dimensional simulations of a region close to the surface of a differentially rotating proto-neutron star in non-ideal magnetohydrodynamics with two different numerical codes. We find that under the conditions prevailing in proto-neutron stars, the MRI can amplify the magnetic field by (only) one order of magnitude. This severely limits the role of MRI channel modes as an agent amplifying the magnetic field in proto-neutron stars starting from small seed fields. Title: Radiative and mechanical feedback into the molecular gas in the Large Magellanic Cloud. I. N159W Authors: Lee, M. -Y.; Madden, S. C.; Lebouteiller, V.; Gusdorf, A.; Godard, B.; Wu, R.; Galametz, M.; Cormier, D.; Le Petit, F.; Roueff, E.; Bron, E.; Carlson, L.; Chevance, M.; Fukui, Y.; Galliano, F.; Hony, S.; Hughes, A.; Indebetouw, R.; Israel, F. P.; Kawamura, A.; Le Bourlot, J.; Lesaffre, P.; Meixner, M.; Muller, E.; Nayak, O.; Onishi, T.; Roman-Duval, J.; Sewiło, M. Bibcode: 2016A&A...596A..85L Altcode: 2016arXiv160604290L We present Herschel SPIRE Fourier Transform Spectrometer (FTS) observations of N159W, an active star-forming region in the Large Magellanic Cloud (LMC). In our observations, a number of far-infrared cooling lines, including carbon monoxide (CO) J = 4 → 3 to J = 12 → 11, [CI] 609 μm and 370 μm, and [NII] 205 μm, are clearly detected. With an aim of investigating the physical conditions and excitation processes of molecular gas, we first construct CO spectral line energy distributions (SLEDs) on 10 pc scales by combining the FTS CO transitions with ground-based low-J CO data and analyze the observed CO SLEDs using non-LTE (local thermodynamic equilibrium) radiative transfer models. We find that the CO-traced molecular gas in N159W is warm (kinetic temperature of 153-754 K) and moderately dense (H2 number density of (1.1-4.5) × 103 cm-3). To assess the impact of the energetic processes in the interstellar medium on the physical conditions of the CO-emitting gas, we then compare the observed CO line intensities with the models of photodissociation regions (PDRs) and shocks. We first constrain the properties of PDRs by modeling Herschel observations of [OI] 145 μm, [CII] 158 μm, and [CI] 370 μm fine-structure lines and find that the constrained PDR components emit very weak CO emission. X-rays and cosmic-rays are also found to provide a negligible contribution to theCO emission, essentially ruling out ionizing sources (ultraviolet photons, X-rays, and cosmic-rays) as the dominant heating source for CO in N159W. On the other hand, mechanical heating by low-velocity C-type shocks with 10 km s-1 appears sufficient enough to reproduce the observed warm CO.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.The final reduced Herschel data (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A85 Title: APSARA: A multi-dimensional unsplit fourth-order explicit Eulerian hydrodynamics code for arbitrary curvilinear grids Authors: Wongwathanarat, A.; Grimm-Strele, H.; Müller, E. Bibcode: 2016A&A...595A..41W Altcode: 2016arXiv160704272W We present a new fourth-order, finite-volume hydrodynamics code named Apsara. The code employs a high-order, finite-volume method for mapped coordinates with extensions for nonlinear hyperbolic conservation laws. Apsara can handle arbitrary structured curvilinear meshes in three spatial dimensions. The code has successfully passed several hydrodynamic test problems, including the advection of a Gaussian density profile and a nonlinear vortex and the propagation of linear acoustic waves. For these test problems, Apsara produces fourth-order accurate results in case of smooth grid mappings. The order of accuracy is reduced to first-order when using the nonsmooth circular grid mapping. When applying the high-order method to simulations of low-Mach number flows, for example, the Gresho vortex and the Taylor-Green vortex, we discover that Apsara delivers superior results to codes based on the dimensionally split, piecewise parabolic method (PPM) widely used in astrophysics. Hence, Apsara is a suitable tool for simulating highly subsonic flows in astrophysics. In the first astrophysical application, we perform implicit large eddy simulations (ILES) of anisotropic turbulence in the context of core collapse supernova (CCSN) and obtain results similar to those previously reported. Title: From ATLASGAL to SEDIGISM: Towards a Complete 3D View of the Dense Galactic Interstellar Medium Authors: Schuller, F.; Urquhart, J.; Bronfman, L.; Csengeri, T.; Bontemps, S.; Duarte-Cabral, A.; Giannetti, A.; Ginsburg, A.; Henning, T.; Immer, K.; Leurini, S.; Mattern, M.; Menten, K.; Molinari, S.; Muller, E.; Sánchez-Monge, A.; Schisano, E.; Suri, S.; Testi, L.; Wang, K.; Wyrowski, F.; Zavagno, A. Bibcode: 2016Msngr.165...27S Altcode: 2016Msngr.165...27U The ATLASGAL survey has provided the first unbiased view of the inner Galactic Plane at sub-millimetre wavelengths. This is the largest ground-based survey of its kind to date, covering 420 square degrees at a wavelength of 870 µm. The reduced data, consisting of images and a catalogue of > 104 compact sources, are available from the ESO Science Archive Facility through the Phase 3 infrastructure. The extremely rich statistics of this survey initiated several follow-up projects, including spectroscopic observations to explore molecular complexity and high angular resolution imaging with the Atacama Large Millimeter/submillimeter Array (ALMA), aimed at resolving individual protostars. The most extensive follow-up project is SEDIGISM, a 3D mapping of the dense interstellar medium over a large fraction of the inner Galaxy. Some notable results of these surveys are highlighted. Title: On the maximum magnetic field amplification by the magnetorotational instability in core-collapse supernovae Authors: Rembiasz, T.; Guilet, J.; Obergaulinger, M.; Cerdá-Durán, P.; Aloy, M. A.; Müller, E. Bibcode: 2016MNRAS.460.3316R Altcode: 2016arXiv160300466R; 2016MNRAS.tmp..888R Whether the magnetorotational instability (MRI) can amplify initially weak magnetic fields to dynamically relevant strengths in core-collapse supernovae is still a matter of active scientific debate. Recent numerical studies have shown that the first phase of MRI growth dominated by channel flows is terminated by parasitic instabilities of the Kelvin-Helmholtz type that disrupt MRI channel flows and quench further magnetic field growth. However, it remains to be properly assessed by what factor the initial magnetic field can be amplified and how it depends on the initial field strength and the amplitude of the perturbations. Different termination criteria leading to different estimates of the amplification factor were proposed within the parasitic model. To determine the amplification factor and test which criterion is a better predictor of the MRI termination, we perform three-dimensional shearing-disc and shearing-box simulations of a region close to the surface of a differentially rotating protoneutron star in non-ideal magnetohydrodynamics with two different numerical codes. We find that independently of the initial magnetic field strength, the MRI channel modes can amplify the magnetic field by, at most, a factor of 100. Under the conditions found in protoneutron stars, a more realistic value for the magnetic field amplification is of the order of 10. This severely limits the role of the MRI channel modes as an agent amplifying the magnetic field in protoneutron stars starting from small seed fields. A further amplification should therefore rely on other physical processes, such as for example an MRI-driven turbulent dynamo. Title: Shear mixing in stellar radiative zones. II. Robustness of numerical simulations Authors: Prat, V.; Guilet, J.; Viallet, M.; Müller, E. Bibcode: 2016A&A...592A..59P Altcode: 2015arXiv151204223P Context. Recent numerical simulations suggest that the model by Zahn (1992, A&A, 265, 115) for the turbulent mixing of chemical elements due to differential rotation in stellar radiative zones is valid.
Aims: We investigate the robustness of this result with respect to the numerical configuration and Reynolds number of the flow.
Methods: We compare results from simulations performed with two different numerical codes, including one that uses the shearing-box formalism. We also extensively study the dependence of the turbulent diffusion coefficient on the turbulent Reynolds number.
Results: The two numerical codes used in this study give consistent results. The turbulent diffusion coefficient is independent of the size of the numerical domain if at least three large turbulent structures fit in the box. Generally, the turbulent diffusion coefficient depends on the turbulent Reynolds number. However, our simulations suggest that an asymptotic regime is obtained when the turbulent Reynolds number is larger than 103.
Conclusions: Shear mixing in the regime of small Péclet numbers can be investigated numerically both with shearing-box simulations and simulations using explicit forcing. Our results suggest that Zahn's model is valid at large turbulent Reynolds numbers. Title: System tests and on-sky commissioning of the GRAVITY-CIAO wavefront sensors Authors: Deen, C.; Kolb, J.; Oberti, S.; Bonnet, H.; Müller, E.; Hubert, Z.; Zins, G.; Delplancke, F.; Haguenauer, P.; Pettazzi, L.; Bourget, P.; Suarez-Valles, M.; Scheithauer, S.; Huber, A.; Esselborn, M.; Clenét, Y.; Gendron, E.; Brandner, W.; Klein, R.; Lenzen, R.; Neumann, Udo; Kulas, M.; Panduro, J.; Ramos, J.; Rohloff, R. -R.; Henning, T.; Perraut, K.; Perrin, G.; Straubmeier, C.; Amorim, A.; Eisenhauer, F. Bibcode: 2016SPIE.9909E..2MD Altcode: GRAVITY is a near-infrared interferometric instrument that allows astronomers to combine the light of the four unit or four auxiliary telescopes of the ESO Very Large Telescope in Paranal, Chile. GRAVITY will deliver extremely precise relative astrometry and spatially resolved spectra. In order to study objects in regions of high extinction (e.g. the Galactic Center, or star forming regions), GRAVITY will use infrared wavefront sensors. The suite of four wavefront sensors located in the Coudé room of each of the unit telescopes are known as the Coudé Integrated Adaptive Optics (CIAO). The CIAO wavefront sensors are being constructed by the Max Planck Institute for Astronomy (MPIA) and are being installed and commissioned at Paranal between February and September of 2016. This presentation will focus on system tests performed in the MPIA adaptive optics laboratory in Heidelberg, Germany in preparation for shipment to Paranal, as well as on-sky data from the commissioning of the first instrument. We will discuss the CIAO instruments, control strategy, optimizations, and performance at the telescope. Title: Termination of the MRI via parasitic instabilities in core-collapse supernovae: influence of numerical methods Authors: Rembiasz, T.; Obergaulinger, M.; Cerdá-Durán, P.; Aloy, M. Á.; Müller, E. Bibcode: 2016JPhCS.719a2009R Altcode: 2016arXiv160505200R We study the influence of numerical methods and grid resolution on the termination of the magnetorotational instability (MRI) by means of parasitic instabilities in threedimensional shearing-disc simulations reproducing typical conditions found in core-collapse supernovae. Whether or not the MRI is able to amplify weak magnetic fields in this context strongly depends, among other factors, on the amplitude at which its growth terminates. The qualitative results of our study do not depend on the numerical scheme. In all our models, MRI termination is caused by Kelvin-Helmholtz instabilities, consistent with theoretical predictions. Quantitatively, however, there are differences, but numerical convergence can be achieved even at relatively low grid resolutions if high-order reconstruction methods are used. Title: Termination of the magnetorotational instability via parasitic instabilities in core-collapse supernovae Authors: Rembiasz, T.; Obergaulinger, M.; Cerdá-Durán, P.; Müller, E.; Aloy, M. A. Bibcode: 2016MNRAS.456.3782R Altcode: 2015arXiv150804799R The magnetorotational instability (MRI) can be a powerful mechanism amplifying the magnetic field in core-collapse supernovae. Whether initially weak magnetic fields can be amplified by this instability to dynamically relevant strengths is still a matter of debate. One of the main uncertainties concerns the process that terminates the growth of the instability. Parasitic instabilities of both Kelvin-Helmholtz and tearing-mode type have been suggested to play a crucial role in this process, disrupting MRI channel flows and quenching magnetic field amplification. We perform two-dimensional and three-dimensional sheering-disc simulations of a differentially rotating protoneutron star layer in non-ideal magnetohydrodynamics with unprecedented high numerical accuracy, finding that Kelvin-Helmholtz parasitic modes dominate tearing modes in the regime of large hydrodynamic and magnetic Reynolds numbers, as encountered close to the surface of protoneutron stars. They also determine the maximum magnetic field stress achievable during the exponential growth of the MRI. Our results are consistent with the theory of parasitic instabilities based on a local stability analysis. To simulate the Kelvin-Helmholtz instabilities properly, a very high numerical resolution is necessary. Using ninth-order spatial reconstruction schemes, we find that at least eight grid zones per MRI channel are necessary to simulate the growth phase of the MRI and reach an accuracy of ∼10 per cent in the growth rate, while more than ∼60 zones per channel are required to achieve convergent results for the value of the magnetic stress at MRI termination. Title: Candidate Filament Collision in the SMC; Energy Distribution within the SFR N66/NGC346 Authors: Muller, E.; Kempen, T.; Mizuno, N.; Kawamura, A.; Minamidani, T. Bibcode: 2015ASPC..499..251M Altcode: The N66 nebula in the SMC is associated with NGC346, the brightest, most magnificent and iconic star-forming region in the metal-poor and CO-underluminous Small Magellanic Cloud. More than half the entire SMC O-star population and 6% of the current-era starformation is located in this small ∼ 80 pc region. The little research undertaken towards N66 focuses on only measurements of the CO and continuum surface-brightness, without a detailed kinematic and energetic emphasis. We explore these aspects here, and discuss a candidate formation scenario for this astonishing, and entirely enigmatic structure in the SMC. Title: Dense Molecular Clumps Associated with the LMC Supergiant Shell LMC 4 & LMC 5 Authors: Fujii, K.; Minamidani, T.; Mizuno, N.; Onishi, T.; Kawamura, A.; Muller, E.; Dawson, J.; Fukui, Y. Bibcode: 2015ASPC..499..255F Altcode: The 12CO(J=3-2/1-0) and 13CO(J=3-2/1-0) observations with ASTE and Mopra telescopes have been carried out toward the giant molecular clouds (GMCs) in the N48/N49 regions in the Large Magellanic Cloud (LMC), which are located at the boundary of two kpc-scale Supergiant Shell (SGS) LMC 4 & LMC 5. The star formation is relatively evolved in the N48 region, which is just located at the boundary of SGSs, than in the N49 region. The clumps in the N48 show higher n(H2) and Tkin than those in the N49, but their densities are not so high as the LMC cluster forming clumps. The collision of two SGSs actually enhances the star formation but further evolution seem to be necessary for subsequent cluster formation. Title: Supernova 1987A: neutrino-driven explosions in three dimensions and light curves Authors: Utrobin, V. P.; Wongwathanarat, A.; Janka, H. -Th.; Müller, E. Bibcode: 2015A&A...581A..40U Altcode: 2014arXiv1412.4122U Context. The well-observed and well-studied type IIP Supernova 1987A (SN 1987A), produced by the explosion of a blue supergiant in the Large Magellanic Cloud, is a touchstone for the evolution of massive stars, the simulation of neutrino-driven explosions, and the modeling of light curves and spectra.
Aims: In the framework of the neutrino-driven explosion mechanism, we study the dependence of explosion properties on the structure of different blue supergiant progenitors and compare the corresponding light curves with observations of SN 1987A.
Methods: Three-dimensional (3D) simulations of neutrino-driven explosions are performed with the explicit, finite-volume, Eulerian, multifluid hydrodynamics code Prometheus, using of four available presupernova models as initial data. At a stage of almost homologous expansion, the hydrodynamical and composition variables of the 3D models are mapped to a spherically symmetric configuration, and the simulations are continued with the implicit, Lagrangian radiation-hydrodynamics code Crab to follow the blast-wave evolution into the SN outburst.
Results: All of our 3D neutrino-driven explosion models, with explosion energies compatible with SN 1987A, produce 56Ni in rough agreement with the amount deduced from fitting the radioactively powered light-curve tail. Two of our models (based on the same progenitor) yield maximum velocities of around 3000 km s-1 for the bulk of ejected 56Ni, consistent with observational data. In all of our models inward mixing of hydrogen during the 3D evolution leads to minimum velocities of hydrogen-rich matter below 100 km s-1, which is in good agreement with spectral observations. However, the explosion of only one of the considered progenitors reproduces the shape of the broad light curve maximum of SN 1987A fairly well.
Conclusions: The considered presupernova models, 3D explosion simulations, and light-curve calculations can explain the basic observational features of SN 1987A, except for those connected to the presupernova structure of the outer stellar layers. All progenitors have presupernova radii that are too large to reproduce the narrow initial luminosity peak, and the structure of their outer layers is not suitable to match the observed light curve during the first 30-40 days. Only one stellar model has a structure of the helium core and the He/H composition interface that enables sufficient outward mixing of 56Ni and inward mixing of hydrogen to produce a good match of the dome-like shape of the observed light-curve maximum, but this model falls short of the helium-core mass of 6 M inferred from the absolute luminosity of the presupernova star. The lack of an adequate presupernova model for the well-studied SN 1987A is a real and pressing challenge for the theory of the evolution of massive stars. Title: The Future of Astronomy and the ALMA Archive Authors: Stoehr, F.; Lacy, M.; Leon, S.; Muller, E.; Kawamura, A. Bibcode: 2015ASPC..495...69S Altcode: 2015adass..24...69S Astronomy is changing as the amount and complexity of data taken grows. We argue that in the future observatories will compete for astronomers to work with their data, that observatories will have to reorient themselves to from providing good data only to providing an excellent end-to-end user-experience with all its implications, that science-grade data-reduction pipelines will become an integral part of the design of a new observatory or instrument and that all this evolution will have a deep impact on how astronomers will do science. We show how ALMA's general design principles are in line with this paradigm and how the ALMA archive fits into this picture. Title: The 2014 ALMA Long Baseline Campaign: An Overview Authors: ALMA Partnership; Fomalont, E. B.; Vlahakis, C.; Corder, S.; Remijan, A.; Barkats, D.; Lucas, R.; Hunter, T. R.; Brogan, C. L.; Asaki, Y.; Matsushita, S.; Dent, W. R. F.; Hills, R. E.; Phillips, N.; Richards, A. M. S.; Cox, P.; Amestica, R.; Broguiere, D.; Cotton, W.; Hales, A. S.; Hiriart, R.; Hirota, A.; Hodge, J. A.; Impellizzeri, C. M. V.; Kern, J.; Kneissl, R.; Liuzzo, E.; Marcelino, N.; Marson, R.; Mignano, A.; Nakanishi, K.; Nikolic, B.; Perez, J. E.; Pérez, L. M.; Toledo, I.; Aladro, R.; Butler, B.; Cortes, J.; Cortes, P.; Dhawan, V.; Di Francesco, J.; Espada, D.; Galarza, F.; Garcia-Appadoo, D.; Guzman-Ramirez, L.; Humphreys, E. M.; Jung, T.; Kameno, S.; Laing, R. A.; Leon, S.; Mangum, J.; Marconi, G.; Nagai, H.; Nyman, L. -A.; Radiszcz, M.; Rodón, J. A.; Sawada, T.; Takahashi, S.; Tilanus, R. P. J.; van Kempen, T.; Vila Vilaro, B.; Watson, L. C.; Wiklind, T.; Gueth, F.; Tatematsu, K.; Wootten, A.; Castro-Carrizo, A.; Chapillon, E.; Dumas, G.; de Gregorio-Monsalvo, I.; Francke, H.; Gallardo, J.; Garcia, J.; Gonzalez, S.; Hibbard, J. E.; Hill, T.; Kaminski, T.; Karim, A.; Krips, M.; Kurono, Y.; Lopez, C.; Martin, S.; Maud, L.; Morales, F.; Pietu, V.; Plarre, K.; Schieven, G.; Testi, L.; Videla, L.; Villard, E.; Whyborn, N.; Zwaan, M. A.; Alves, F.; Andreani, P.; Avison, A.; Barta, M.; Bedosti, F.; Bendo, G. J.; Bertoldi, F.; Bethermin, M.; Biggs, A.; Boissier, J.; Brand, J.; Burkutean, S.; Casasola, V.; Conway, J.; Cortese, L.; Dabrowski, B.; Davis, T. A.; Diaz Trigo, M.; Fontani, F.; Franco-Hernandez, R.; Fuller, G.; Galvan Madrid, R.; Giannetti, A.; Ginsburg, A.; Graves, S. F.; Hatziminaoglou, E.; Hogerheijde, M.; Jachym, P.; Jimenez Serra, I.; Karlicky, M.; Klaasen, P.; Kraus, M.; Kunneriath, D.; Lagos, C.; Longmore, S.; Leurini, S.; Maercker, M.; Magnelli, B.; Marti Vidal, I.; Massardi, M.; Maury, A.; Muehle, S.; Muller, S.; Muxlow, T.; O'Gorman, E.; Paladino, R.; Petry, D.; Pineda, J. E.; Randall, S.; Richer, J. S.; Rossetti, A.; Rushton, A.; Rygl, K.; Sanchez Monge, A.; Schaaf, R.; Schilke, P.; Stanke, T.; Schmalzl, M.; Stoehr, F.; Urban, S.; van Kampen, E.; Vlemmings, W.; Wang, K.; Wild, W.; Yang, Y.; Iguchi, S.; Hasegawa, T.; Saito, M.; Inatani, J.; Mizuno, N.; Asayama, S.; Kosugi, G.; Morita, K. -I.; Chiba, K.; Kawashima, S.; Okumura, S. K.; Ohashi, N.; Ogasawara, R.; Sakamoto, S.; Noguchi, T.; Huang, Y. -D.; Liu, S. -Y.; Kemper, F.; Koch, P. M.; Chen, M. -T.; Chikada, Y.; Hiramatsu, M.; Iono, D.; Shimojo, M.; Komugi, S.; Kim, J.; Lyo, A. -R.; Muller, E.; Herrera, C.; Miura, R. E.; Ueda, J.; Chibueze, J.; Su, Y. -N.; Trejo-Cruz, A.; Wang, K. -S.; Kiuchi, H.; Ukita, N.; Sugimoto, M.; Kawabe, R.; Hayashi, M.; Miyama, S.; Ho, P. T. P.; Kaifu, N.; Ishiguro, M.; Beasley, A. J.; Bhatnagar, S.; Braatz, J. A., III; Brisbin, D. G.; Brunetti, N.; Carilli, C.; Crossley, J. H.; D'Addario, L.; Donovan Meyer, J. L.; Emerson, D. T.; Evans, A. S.; Fisher, P.; Golap, K.; Griffith, D. M.; Hale, A. E.; Halstead, D.; Hardy, E. J.; Hatz, M. C.; Holdaway, M.; Indebetouw, R.; Jewell, P. R.; Kepley, A. A.; Kim, D. -C.; Lacy, M. D.; Leroy, A. K.; Liszt, H. S.; Lonsdale, C. J.; Matthews, B.; McKinnon, M.; Mason, B. S.; Moellenbrock, G.; Moullet, A.; Myers, S. T.; Ott, J.; Peck, A. B.; Pisano, J.; Radford, S. J. E.; Randolph, W. T.; Rao Venkata, U.; Rawlings, M. G.; Rosen, R.; Schnee, S. L.; Scott, K. S.; Sharp, N. K.; Sheth, K.; Simon, R. S.; Tsutsumi, T.; Wood, S. J. Bibcode: 2015ApJ...808L...1A Altcode: 2015arXiv150404877P A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ∼15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from 2014 September to late November, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C 138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at ∼350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy.

. Title: Three-dimensional simulations of core-collapse supernovae: from shock revival to shock breakout Authors: Wongwathanarat, A.; Müller, E.; Janka, H. -Th. Bibcode: 2015A&A...577A..48W Altcode: 2014arXiv1409.5431W We present three-dimensional hydrodynamic simulations of the evolution of core-collapse supernovae (SN) from blast-wave initiation by the neutrino-driven mechanism to shock breakout from the stellar surface, using an axis-free Yin-Yang grid and considering two 15 M red supergiants (RSG) and two blue supergiants (BSG) of 15 M and 20 M. We demonstrate that the metal-rich ejecta in homologous expansion still carry fingerprints of asymmetries at the beginning of the explosion, but the final metal distribution is massively affected by the detailed progenitor structure. The most extended and fastest metal fingers and clumps are correlated with the biggest and fastest-rising plumes of neutrino-heated matter, because these plumes most effectively seed the growth of Rayleigh-Taylor (RT) instabilities at the C+O/He and He/H composition-shell interfaces after the passage of the SN shock. The extent of radial mixing, global asymmetry of the metal-rich ejecta, RT-induced fragmentation of initial plumes to smaller-scale fingers, and maximum Ni and minimum H velocities depend not only on the initial asphericity and explosion energy (which determine the shock and initial Ni velocities), but also on the density profiles and widths of C+O core and He shell and on the density gradient at the He/H transition, which leads to unsteady shock propagation and the formation of reverse shocks. Both RSG explosions retain a large global metal asymmetry with pronounced clumpiness and substructure, deep penetration of Ni fingers into the H-envelope (with maximum velocities of 4000-5000 km s-1 for an explosion energy around 1.5 bethe) and efficient inward H-mixing. While the 15 M BSG shares these properties (maximum Ni speeds up to ~3500 km s-1), the 20 M BSG develops a much more roundish geometry without pronounced metal fingers (maximum Ni velocities only ~2200 km s-1) because of reverse-shock deceleration and insufficient time for strong RT growth and fragmentation at the He/H interface. Title: Erratum: “The Herschel Inventory of the Agents of Galaxy Evolution (Heritage) in the Magellanic Clouds, a Herschel Open Time Key Program” (2013, AJ, 146, 62) Authors: Meixner, M.; Panuzzo, P.; Roman-Duval, J.; Engelbracht, C.; Babler, B.; Seale, J.; Hony, S.; Montiel, E.; Sauvage, M.; Gordon, K.; Misselt, K.; Okumura, K.; Chanial, P.; Beck, T.; Bernard, J. -P.; Bolatto, A.; Bot, C.; Boyer, M. L.; Carlson, L. R.; Clayton, G. C.; Chen, C. -H. R.; Cormier, D.; Fukui, Y.; Galametz, M.; Galliano, F.; Hora, J. L.; Hughes, A.; Indebetouw, R.; Israel, F. P.; Kawamura, A.; Kemper, F.; Kim, S.; Kwon, E.; Lebouteiller, V.; Li, A.; Long, K. S.; Madden, S. C.; Matsuura, M.; Muller, E.; Oliveira, J. M.; Onishi, T.; Otsuka, M.; Paradis, D.; Poglitsch, A.; Reach, W. T.; Robitaille, T. P.; Rubio, M.; Sargent, B.; Sewiło, M.; Skibba, R.; Smith, L. J.; Srinivasan, S.; Tielens, A. G. G. M.; van Loon, J. Th.; Whitney, B. Bibcode: 2015AJ....149...88M Altcode: No abstract at ADS Title: Modulating magnetar emission by magneto-elastic oscillations Authors: Gabler, M.; Cerdá-Durán, P.; Font, J. A.; Stergioulas, N.; Müller, E. Bibcode: 2014AN....335..240G Altcode: We present a new numerical tool to calculate the emission of highly magnetized neutron stars (magnetars) and apply it to describe the quasi-periodic oscillations (QPOs) observed in magnetar giant flares. In previous work we have developed a model of magneto-elastic oscillations of magnetars that allows to reproduce the observed frequencies. These QPOs can couple to the star's exterior through the magnetic field and induce currents in the magnetosphere that provide scattering targets for resonant cyclotron scattering of the photons. The scattering is calculated with a Monte-Carlo approach and it is coupled to a code that calculates the momentum distribution of the charge carriers as an one-dimensional accelerator problem. As a first test of the method we calculate the modulation of the quiescent emission of the neutron star by the magneto-elastic QPOs for a prescribed momentum distribution of the charge carriers. The necessary amplitudes of the QPOs at the surface of the star to modulate the emission significantly are {⪉ 1} km. Title: Hydrodynamic simulations of the interaction of supernova shock waves with a clumpy environment: the case of the RX J0852.0-4622 (Vela Jr) supernova remnant Authors: Obergaulinger, M.; Iyudin, A. F.; Müller, E.; Smoot, G. F. Bibcode: 2014MNRAS.437..976O Altcode: 2013MNRAS.tmp.2632O; 2014arXiv1408.0895O Observations in all electromagnetic bands show that many supernova remnants (SNRs) have a very aspherical shape. This can be the result of asymmetries in the supernova explosion or a clumpy circumstellar medium. We study the generation of inhomogeneities and the mixing of elements arising from these two sources in multidimensional hydrodynamic simulations of the propagation of a supernova blast wave into a cloudy environment. We model a specific SNR, Vela Jr (RX J0852.0-4622). By comparing our results with recent observations, we can constrain the properties of the explosion. We find that a very energetic explosion of several 1051 erg occurring roughly about 800 years ago is consistent with the shape and emission of the SNR, as well as a supernova with an energy closer to the canonical value of 1051 erg a few thousand years ago. Title: MALT90: The Millimetre Astronomy Legacy Team 90 GHz Survey Authors: Jackson, J. M.; Rathborne, J. M.; Foster, J. B.; Whitaker, J. S.; Sanhueza, P.; Claysmith, C.; Mascoop, J. L.; Wienen, M.; Breen, S. L.; Herpin, F.; Duarte-Cabral, A.; Csengeri, T.; Longmore, S. N.; Contreras, Y.; Indermuehle, B.; Barnes, P. J.; Walsh, A. J.; Cunningham, M. R.; Brooks, K. J.; Britton, T. R.; Voronkov, M. A.; Urquhart, J. S.; Alves, J.; Jordan, C. H.; Hill, T.; Hoq, S.; Finn, S. C.; Bains, I.; Bontemps, S.; Bronfman, L.; Caswell, J. L.; Deharveng, L.; Ellingsen, S. P.; Fuller, G. A.; Garay, G.; Green, J. A.; Hindson, L.; Jones, P. A.; Lenfestey, C.; Lo, N.; Lowe, V.; Mardones, D.; Menten, K. M.; Minier, V.; Morgan, L. K.; Motte, F.; Muller, E.; Peretto, N.; Purcell, C. R.; Schilke, P.; Bontemps, Schneider-N.; Schuller, F.; Titmarsh, A.; Wyrowski, F.; Zavagno, A. Bibcode: 2013PASA...30...57J Altcode: 2013arXiv1310.1131J The Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey aims to characterise the physical and chemical evolution of high-mass star-forming clumps. Exploiting the unique broad frequency range and on-the-fly mapping capabilities of the Australia Telescope National Facility Mopra 22 m single-dish telescope 1 , MALT90 has obtained 3' × 3' maps towards ~2 000 dense molecular clumps identified in the ATLASGAL 870 μm Galactic plane survey. The clumps were selected to host the early stages of high-mass star formation and to span the complete range in their evolutionary states (from prestellar, to protostellar, and on to H II regions and photodissociation regions). Because MALT90 mapped 16 lines simultaneously with excellent spatial (38 arcsec) and spectral (0.11 km s-1) resolution, the data reveal a wealth of information about the clumps' morphologies, chemistry, and kinematics. In this paper we outline the survey strategy, observing mode, data reduction procedure, and highlight some early science results. All MALT90 raw and processed data products are available to the community. With its unprecedented large sample of clumps, MALT90 is the largest survey of its type ever conducted and an excellent resource for identifying interesting candidates for high-resolution studies with ALMA. Title: The HERSCHEL Inventory of The Agents of Galaxy Evolution in the Magellanic Clouds, a Herschel Open Time Key Program Authors: Meixner, M.; Panuzzo, P.; Roman-Duval, J.; Engelbracht, C.; Babler, B.; Seale, J.; Hony, S.; Montiel, E.; Sauvage, M.; Gordon, K.; Misselt, K.; Okumura, K.; Chanial, P.; Beck, T.; Bernard, J. -P.; Bolatto, A.; Bot, C.; Boyer, M. L.; Carlson, L. R.; Clayton, G. C.; Chen, C. -H. R.; Cormier, D.; Fukui, Y.; Galametz, M.; Galliano, F.; Hora, J. L.; Hughes, A.; Indebetouw, R.; Israel, F. P.; Kawamura, A.; Kemper, F.; Kim, S.; Kwon, E.; Lebouteiller, V.; Li, A.; Long, K. S.; Madden, S. C.; Matsuura, M.; Muller, E.; Oliveira, J. M.; Onishi, T.; Otsuka, M.; Paradis, D.; Poglitsch, A.; Reach, W. T.; Robitaille, T. P.; Rubio, M.; Sargent, B.; Sewiło, M.; Skibba, R.; Smith, L. J.; Srinivasan, S.; Tielens, A. G. G. M.; van Loon, J. Th.; Whitney, B. Bibcode: 2013AJ....146...62M Altcode: We present an overview of the HERschel Inventory of The Agents of Galaxy Evolution (HERITAGE) in the Magellanic Clouds project, which is a Herschel Space Observatory open time key program. We mapped the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) at 100, 160, 250, 350, and 500 μm with the Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer (PACS) instruments on board Herschel using the SPIRE/PACS parallel mode. The overriding science goal of HERITAGE is to study the life cycle of matter as traced by dust in the LMC and SMC. The far-infrared and submillimeter emission is an effective tracer of the interstellar medium (ISM) dust, the most deeply embedded young stellar objects (YSOs), and the dust ejected by the most massive stars. We describe in detail the data processing, particularly for the PACS data, which required some custom steps because of the large angular extent of a single observational unit and overall the large amount of data to be processed as an ensemble. We report total global fluxes for the LMC and SMC and demonstrate their agreement with measurements by prior missions. The HERITAGE maps of the LMC and SMC are dominated by the ISM dust emission and bear most resemblance to the tracers of ISM gas rather than the stellar content of the galaxies. We describe the point source extraction processing and the criteria used to establish a catalog for each waveband for the HERITAGE program. The 250 μm band is the most sensitive and the source catalogs for this band have ~25,000 objects for the LMC and ~5500 objects for the SMC. These data enable studies of ISM dust properties, submillimeter excess dust emission, dust-to-gas ratio, Class 0 YSO candidates, dusty massive evolved stars, supernova remnants (including SN1987A), H II regions, and dust evolution in the LMC and SMC. All images and catalogs are delivered to the Herschel Science Center as part of the community support aspects of the project. These HERITAGE images and catalogs provide an excellent basis for future research and follow up with other facilities. Title: The CoCoNuT code: from neutron star oscillations to supernova explosions Authors: Cerdá-Durán, P.; Gabler, M.; Müller, E.; Font, J. A.; Stergioulas, N.; Obergaulinger, M.; Aloy, M. A.; DeBrye, N.; Cordero-Carrión, I.; Ibáñez, J. M. Bibcode: 2013hsa7.conf..940C Altcode: CoCoNuT is a numerical code, that evolves the General relativistic magneto-hydrodynamics equations coupled to the Einstein equations in the CFC approximation. Its main purpose is to simulate astrophysical scenarios in which strong gravity is important such as the collapse of massive stars and the evolution of neutron stars. I review recent results of the numerical code regarding neutron star oscillations and core collapse supernova and its observational consequences. Title: Modulating magnetar emission by magneto-elastic oscillations Authors: Gabler, M.; Cerdá-Durán, P.; Font, J.; Stergioulas, N.; Müller, E. Bibcode: 2013ffep.confE..23G Altcode: No abstract at ADS Title: Three-dimensional neutrino-driven supernovae: Neutron star kicks, spins, and asymmetric ejection of nucleosynthesis products Authors: Wongwathanarat, A.; Janka, H. -Th.; Müller, E. Bibcode: 2013A&A...552A.126W Altcode: 2012arXiv1210.8148W We present three-dimensional (3D) simulations of supernova explosions of nonrotating stars, triggered by the delayed neutrino-heating mechanism with a suitable choice of the core-neutrino luminosity. Our results show that asymmetric mass ejection caused by hydrodynamic instabilities can accelerate the neutron star (NS) up to recoil velocities of more than 700 km s-1 by the "gravitational tug-boat mechanism", which is sufficient to explain most observed pulsar space velocities. The associated NS spin periods for our nonrotating progenitors are about 100 ms to 8000 ms without any obvious correlation between spin and kick magnitudes or directions. This suggests that faster spins and a possible spin-kick alignment might require angular momentum in the progenitor core prior to collapse. Our simulations for the first time demonstrate a clear correlation between the size of the NS kick and anisotropic production and distribution of heavy elements created by explosive burning behind the shock. In the case of large pulsar kicks, the explosion is significantly stronger opposite to the kick vector. Therefore the bulk of the explosively fused iron-group elements, in particular nickel, are ejected mostly in large clumps against the kick direction. This contrasts with the case of low recoil velocity, where the nickel-rich lumps are more isotropically distributed. Explosively produced intermediate-mass nuclei heavier than 28Si (like 40Ca and 44Ti) also exhibit significant enhancement in the hemisphere opposite to the direction of fast NS motion, while the distribution of 12C, 16O, and 20Ne is not affected, and that of 24Mg only marginally. Mapping the spatial distribution of the heavy elements in supernova remnants with identified pulsar motion may offer an important diagnostic test of the kick mechanism. Unlike kick scenarios based on anisotropic neutrino emission, our hydrodynamical acceleration model predicts enhanced ejection of iron-group elements and of their nuclear precursors in the opposite direction to the NS recoil. Title: Resolved Schmidt-Kennicutt Relation for Star Forming Regions in the Galaxy and Magellanic Clouds Authors: Chen, C. -H. R.; Indebetouw, R.; Muller, E.; Messineo, M.; Menten, K. M.; SAGE-SMC Team Bibcode: 2013IAUS..292..307C Altcode: The relationship between star formation rate (SFR) and the gas surface density (Σgas) is one of the most critical links between star formation and galaxy evolution. The observed SFR- Σgas relation, the "Schmidt-Kennicutt (S-K) law", is tight when properties are averaged over kpc, but breaks down at the scale of giant molecular clouds (GMCs). To understand the physics governing the variations at GMC scales and the tight correlation at kpc scales, spatially and temporally resolved data covering a wide range of linear scale are needed. We have used the Spitzer surveys of the Large Magellanic Cloud and Magellanic Bridge to identify massive young stellar objects (YSOs), estimate "instantaneous" SFRs, and compare them to the S-K relation. These instantaneous SFRs are further compared to that estimated from integrated Hα and 24 μm luminosities to examine how SFRs vary on 10 Myr timescales. We have also used SINFONI near-IR integral field spectra of two Galactic mini-starbursts W31 and W43 to determine their underlying massive stellar content, estimate the SFRs, and compare to the S-K relation. To investigate evironmental effects on star formation, we have used complete YSO samples in the LMC and the Bridge to estimate global star formation efficiencies (SFE) in these two systems. Title: Comet 168P/Hergenrother Authors: Hergenrother, C. W.; Mueller, E. A.; Sekanina, Z. Bibcode: 2012CBET.3318....1H Altcode: Carl W. Hergenrother, Lunar and Planetary Laboratory, University of Arizona, reports the detection of an additional companion (denoted G) to those announced on CBET 3295. Co-added R-band images were obtained with the Kitt Peak 2.1-m reflector by Yanga Fernandez and Emily Kramer (University of Central Florida); the data were made available by Beatrice E. A. Mueller (Planetary Science Institute). Companion G was detected at the following separations and position angles from the central condensation of the primary: Nov. 11.35 UT, 9".7, 168.0 deg; Nov. 12.29, 9".8, 163.9 deg. On Nov. 11.35, the companion was diffuse with no apparent central condensation and elongated towards the anti-solar direction with dimensions of 2".4 by 1".8. On Nov. 12.29, the companion appeared fainter, with dimensions of 1".8 x 1".5, elongated towards the anti-solar direction. Z. Sekanina, Jet Propulsion Laboratory, reports that the motion of this additional fragment G is consistent with the separation from the primary nucleus A at the beginning of September, with a very low velocity of about 0.1 m/s. The fragment was subjected to a nongravitational deceleration of 15 +/- 1 units of 10**-5} solar attraction. Although the accuracy of the results is not high, it appears that this is the only fragment whose separation dates back to the first outburst and must have survived for at least 10 weeks. In terms of the nongravitational deceleration, this is the only fragment that rivals fragment B. Predicted separation distances of component G from component A and position angles at 0 h ET: Nov. 29, 12".0, 167 deg; Dec. 9, 12".8, 170 deg; Dec. 19, 13".2, 176 deg; Dec. 29, 13".5, 183 deg. Title: Giant Molecular Clouds and Star Formation in the Tidal Molecular Arm of NGC 4039 Authors: Espada, D.; Komugi, S.; Muller, E.; Nakanishi, K.; Saito, M.; Tatematsu, K.; Iguchi, S.; Hasegawa, T.; Mizuno, N.; Iono, D.; Matsushita, S.; Trejo, A.; Chapillon, E.; Takahashi, S.; Su, Y. N.; Kawamura, A.; Akiyama, E.; Hiramatsu, M.; Nagai, H.; Miura, R. E.; Kurono, Y.; Sawada, T.; Higuchi, A. E.; Tachihara, K.; Saigo, K.; Kamazaki, T. Bibcode: 2012ApJ...760L..25E Altcode: 2012arXiv1211.0767E The properties of tidally induced arms provide a means to study molecular cloud formation and the subsequent star formation under environmental conditions which, in principle, are different from quasi-stationary spiral arms. We report the properties of a newly discovered molecular gas arm of likely tidal origin at the south of NGC 4039 and the overlap region in the Antennae galaxies, with a resolution of 1farcs68 × 0farcs85, using the Atacama Large Millimeter/submillimeter Array science verification CO(2-1) data. The arm extends 3.4 kpc (34'') and is characterized by widths of lsim200 pc (2'') and velocity widths of typically ΔV ~= 10-20 km s-1. About 10 clumps are strung out along this structure, most of them unresolved, with average surface densities of Σgas ~= 10-100 M pc-2, and masses of (1-8)×106 M . These structures resemble the morphology of beads on a string, with an almost equidistant separation between the beads of about 350 pc, which may represent a characteristic separation scale for giant molecular associations. We find that the star formation efficiency at a resolution of 6''(600 pc) is in general a factor of 10 higher than in disk galaxies and other tidal arms and bridges. This arm is linked, based on the distribution and kinematics, to the base of the western spiral arm of NGC 4039, but its morphology is different to that predicted by high-resolution simulations of the Antennae galaxies. Title: Comet 168P/Hergenrother Authors: Mueller, E. A.; Stevenson, R. A.; Bauer, J. M.; Masiero, J. R.; Mainzer, A. K.; Sekanina, Z.; Sostero, G.; Hergenrother, C. W. Bibcode: 2012CBET.3295....5M Altcode: Hergenrother also reports four separate companions to 168P observed in data taken between Oct. 26.42 and Nov. 8.29 UT. The data for all dates from the Kitt Peak 2.1-m reflector were obtained by Yanga Fernandez and Emily Kramer and made available by Beatrice E. A. Mueller. Data from the Faulkes 2.0-m reflector were obtained by Sostero et al. (see above) on Oct. 26, by the Dollar Academy and Queen's College on Nov. 2, and by the Maui Community College on Nov. 3 as part of Faulkes Telescope Education project. Date UT P.A. Sep. Comp. Telescope/ 2012 (deg) (") measurer Oct. 26.42 191.1 2.1 B Faulkes/Hergenrother Nov. 2.44 167.4 3.3 B Faulkes/Hergenrother 3.28 165.3 3.1 B Faulkes/Hergenrother 6.28 160.9 3.3 B Faulkes/Hergenrother 6.30 164.8 3.6 B Kitt Peak/Hergenrother 7.30 162.4 3.6 B Kitt Peak/Hergenrother 7.32 165.6 3.5 B Kitt Peak/Hergenrother Oct. 26.42 139.8 3.8 C Faulkes/Hergenrother Nov. 2.44 133.7 5.8 C Faulkes/Hergenrother 3.28 131.7 6.4 C Faulkes/Hergenrother Nov. 2.44 159.3 5.2 E Kitt Peak/Hergenrother 3.28 151.0 5.0 E Kitt Peak/Hergenrother 7.31 159.1 6.0 E Kitt Peak/Hergenrother 8.27 164.0 5.7 E Kitt Peak/Hergenrother 8.29 165.3 5.7 E Kitt Peak/Hergenrother Nov. 6.28 148.3 9.1 F Kitt Peak/Hergenrother 6.30 149.1 9.3 F Kitt Peak/Hergenrother 7.31 143.9 9.5 F Kitt Peak/Hergenrother R. A. Stevenson, J. M. Bauer, J. R. Masiero, and A. K. Mainzer, Jet Propulsion Laboratory, report CCD observations of comet 168P taken from the Gemini-North telescope atop Mauna Kea, Hawaii, following the report by Sostero et al. (see above) of the outburst and detection of a fragement on Oct. 26.4 UT. Fragment B was detected 2".4 from the primary nuclear condensation on Oct. 28.4 at a position angle of 172.9 deg using 10-s exposures; the brightness of the fragment is 29 percent of the brightest region, which is presumed to be the location of the nucleus. Two additional fragments were detected in 30-s (unstacked) exposures taken on Nov. 2.3: Fragment B was detected 2".9 from the primary nuclear condensation at a position angle of 162.5 deg, with a relative brightness of 27 percent with respect to the nucleus-centered region. Fragment C was detected 6".2 from the nucleus- centered region at a position angle of 132.1 deg with a brightness of 25 percent relative to the nucleus-centered region. Fragment D was detected 11".4 from the nuclear condensation at a position angle of 145.1 deg with a relative brightness of 9 percent to the nucleus-centered region. All fragments appear diffuse and without central condensations. Brightnesses were measured using sky-subtracted aperture photometry; apertures were 1".022 in radius (with projected on-sky radii of 399 and 422 km for Oct. 28 and Nov. 2, respectively). Fragment B is separating from the primary nuclear condensation with a projected on-sky velocity of 0.6 +/- 0.1 m/s (1-sigma uncertainty), measured using r-band (630 nm) data from the 8-m Gemini-North telescope (Oct. 28.4 and Nov. 2.3) and J-band (1.25-micron) and H-band (1.651-micron) images from the 3.5-m WIYN telescope (Oct. 29.2, 30.1, and Nov. 1.1). Z. Sekanina, Jet Propulsion Laboratory, reports that four of the five companions apparently broke off from the primary nucleus A. Based on 9 offsets from Oct. 26-Nov. 7, companion B was found to have separated on Sept. 17.5 +/- 2.5 UT with a velocity of 0.18 +/- 0.05 m/s and was subjected to a nongravitational deceleration of 15 +/- 3 units of 10**-5} solar attraction. Very similar solutions were obtained on the assumption that the separation of B coincided with the onset of an outburst on Sept. 22. For companion C, from four offsets between Oct. 26 and Nov. 3, Sekanina derived a separation on Oct. 7.0 +/- 1.5 UT, with a velocity of 0.3 +/- 0.1 m/s, and a deceleration of 53 +/- 12 units. Very similar solutions resulted assuming that the separation of C coincided with the onset of another outburst, on October 1. For companion D, the offset from Nov. 2 gave only very approximate parameters, a separation around Sept. 28 (probably coinciding with the same outburst as the separation of C) and a deceleration of 70 units. Companion E does not appear to have derived from A, but it may have split off from B within days after B broke off from A. Companion F was found to have separated from A on Sept. 24 (again at about the time of the outburst of Sept. 22) and was subjected to a deceleration of about 40 units. As the mass of material moved in the direction in which fragment C also appeared, and fragment C split off around the time of the Oct. 1 outburst, the mass of material was also a product of that same outburst. The apparent tendency of some companions to grow elongated with time suggests that they already represent clusters of subfragments subjected to a range of decelerations, thus entering an advanced phase of disintegration. Because all the companions appear to be short-lived (as also implied by their high decelerations), the following ephemerides are terminated by the end of November. Predicted separation distances from nucleus A and position angles at 0h ET: Nov. 9, 3".9, 163 deg (B); 8".4, 133 deg (C); 15".2, 144 deg (D); 6".1, 159 deg (E); 10".1, 147 deg (F); Nov. 19, 5".2, 160 deg (B); 12".0, 133 deg (C); 20".6, 144 deg (D); 8".0, 157 deg (E); 13".4, 146 deg (F); Nov. 29, 6".2, 161 deg (B); 15".1, 135 deg (C); 25".0, 146 deg (D); 9".5, 158 deg (E); 16'.0, 148 deg (F). Title: On multigrid solution of the implicit equations of hydrodynamics. Experiments for the compressible Euler equations in general coordinates Authors: Kifonidis, K.; Müller, E. Bibcode: 2012A&A...544A..47K Altcode:
Aims: We describe and study a family of new multigrid iterative solvers for the multidimensional, implicitly discretized equations of hydrodynamics. Schemes of this class are free of the Courant-Friedrichs-Lewy condition. They are intended for simulations in which widely differing wave propagation timescales are present. A preferred solver in this class is identified. Applications to some simple stiff test problems that are governed by the compressible Euler equations, are presented to evaluate the convergence behavior, and the stability properties of this solver. Algorithmic areas are determined where further work is required to make the method sufficiently efficient and robust for future application to difficult astrophysical flow problems.
Methods: The basic equations are formulated and discretized on non-orthogonal, structured curvilinear meshes. Roe's approximate Riemann solver and a second-order accurate reconstruction scheme are used for spatial discretization. Implicit Runge-Kutta (ESDIRK) schemes are employed for temporal discretization. The resulting discrete equations are solved with a full-coarsening, non-linear multigrid method. Smoothing is performed with multistage-implicit smoothers. These are applied here to the time-dependent equations by means of dual time stepping.
Results: For steady-state problems, our results show that the efficiency of the present approach is comparable to the best implicit solvers for conservative discretizations of the compressible Euler equations that can be found in the literature. The use of red-black as opposed to symmetric Gauss-Seidel iteration in the multistage-smoother is found to have only a minor impact on multigrid convergence. This should enable scalable parallelization without having to seriously compromise the method's algorithmic efficiency. For time-dependent test problems, our results reveal that the multigrid convergence rate degrades with increasing Courant numbers (i.e. time step sizes). Beyond a Courant number of nine thousand, even complete multigrid breakdown is observed. Local Fourier analysis indicates that the degradation of the convergence rate is associated with the coarse-grid correction algorithm. An implicit scheme for the Euler equations that makes use of the present method was, nevertheless, able to outperform a standard explicit scheme on a time-dependent problem with a Courant number of order 1000.
Conclusions: For steady-state problems, the described approach enables the construction of parallelizable, efficient, and robust implicit hydrodynamics solvers. The applicability of the method to time-dependent problems is presently restricted to cases with moderately high Courant numbers. This is due to an insufficient coarse-grid correction of the employed multigrid algorithm for large time steps. Further research will be required to help us to understand and overcome the observed multigrid convergence difficulties for time-dependent problems. Title: Magneto-elastic Oscillations and Magnetar QPOs Authors: Stergioulas, N.; Gabler, M.; Cerdá-Durán, P.; Font, J. A.; Müller, E. Bibcode: 2012ASPC..459..167S Altcode: The origin of the quasi-periodic oscillations (QPOs) observed in the giant flares of soft gamma-ray repeaters (SGRs) remains uncertain. Current models explore the idea that long-term quasi-periodic oscillations are trapped at the turning points of the continuum of torsional magneto-elastic oscillations in the magnetar's interior. After reviewing recent work in this field, we describe our latest efforts using two-dimensional, general-relativistic, magneto-hydrodynamical simulations, coupled to evolutions of shear waves in the solid crust, in order to explore the viability of this model when a purely dipolar magnetic field is assumed. We demonstrate the existence of three different regimes (a) B < 5 × 1013 G, where crustal shear modes dominate the evolution; (b) 5 × 1013 G < B < 1015 G, where Alfvén QPOs are mainly confined to the core of the star and the crustal shear modes are damped very efficiently; and (c) B > 1015 G, where magneto-elastic oscillations reach the surface and approach the behavior of purely Alfvén QPOs. Our results do not leave much room for a crustal-mode interpretation of observed QPOs in SGR giant flares, in the case of a purely dipolar magnetic field. On the other hand, the observed QPOs could originate from Alfvén-like, global, turning-point QPOs in models with dipolar magnetic field strengths in the narrow range of 5 × 1015 G ≤ B ≤ 1.4 × 1016 G. To agree with estimates for magnetic field strengths in known magnetars, a more complicated magnetic field structure or superfluidity of the neutrons and superconductivity of the protons should be taken into account. Title: Three-dimensional Core-Collapse Supernova Simulations on the Yin-Yang Grid Authors: Wongwathanarat, A.; Janka, H.; Müller, E. Bibcode: 2012ASPC..453...95W Altcode: We perform a set of neutrino-driven core collapse supernova simulations in three dimensions studying the hydrodynamical neutron star (NS) kick mechanism. The computational cost is reduced significantly with the help of an axis-free overlapping grid technique in spherical geometry called the “Yin-Yang” grid. Our simulations follow the evolution of core collapse supernovae from 15 ms after bounce until approximately 1.4 s later. For the first time in three dimensions, our results produce neutron star kick velocities up to ∼600 km/s. Such a high kick velocity results from the highly asymmetric mass distribution in the post-shock region exerting a net gravitational pull on the proto-neutron star on a timescale of a few seconds. With this kick scenario proposed by Scheck et al., NS recoil velocities larger than ∼1000 km/s might as well be possible but require a larger set of models for statistical reasons (connected with the stochastic development of asymmetries). Our simulations also confirm an enhanced production of heavy elements in the direction roughly opposite to the NS recoil direction. This produces a detectable hemispheric asymmetry in the distribution of heavy elements which can be used to constrain the NS kick mechanism. Title: 2012 LT7 = 2009 MH1 Authors: Fuse, T.; Miyazaki, S.; Spencer, J. R.; Tholen, D. J.; Toshida, F.; Buie, M. W.; Borncamp, D. M.; Gay, P. L.; Wasserman, L. H.; Karoji, H.; Kinoshita, D.; Yanagisawa, T.; Furusawa, H.; Yoshida, F.; Yamashida, T.; Tajitsu, A.; Little, P.; McMahon, C.; Lee, A.; Scheulen, F.; Sauro, C.; Robinson, C.; Berry, S.; Abbate, T.; Abrahamson, T.; Adam, M.; Adamson, J.; Agbedor, A.; Alexander, B.; Allan, U.; Alldredge, X.; Allen, A. M. H.; Alton, D.; Alves, M. P.; Alves, V. S.; Amerongen, O.; Anderson, W. L.; Andrews, J.; Anstett, M.; Applebaum, K.; Arrington, J.; Ashton, E. T. F.; Astl, W.; Atkins, L. G.; Badker, K.; Badnaruk, B.; Baeten, E.; Bailey, R. C.; Balick, R.; Ball, J. L.; Barnett, B. E.; Bartel, J. S.; Bartholomew, C.; Baumgaertner, P.; Becker, A.; Bedard, E.; Beer, I.; Begg, J.; Begonja, J.; Bel, P.; Bevc, J.; Bezugly, V. A.; Bianchini, G.; Biel, M.; Bigelow, B.; Billiani, M.; Bishop, J.; Blanaru, M. C.; Blystone, S.; Boden, G.; Boesch, T.; Bohnes, R.; Boland, C.; Bomeny, F.; Borck, J.; Boschat, M.; Boscher, G. P. A.; Boutilier, M. A.; Boyd, S.; Bradford, N. B.; Bratcher, S.; Brayshaw, P.; Brinkmann, A.; Brittain, C.; Brogan, D.; Brooks, R.; Browne, D.; Brydon, T.; Burluraux, D.; Butler, C.; Caado, P.; Cairns, N. G.; Callebout, F.; Cameron, D.; Campbell, P.; Campos, J.; Candeias, J.; Caracciolo, A.; Carlino, S.; Carpenter, A.; Carrascal, C.; Carruthers, J.; Carsenty, U.; Castro, F.; Chadwick, L. D.; Chaghafi, E.; Chamberlain, B.; Champion, K.; Chandler, C.; Cheng, J. K. H.; Chestnov, D.; Chinery, C.; Chisholm, J.; CIvinskas, A.; Clark, A.; Cleaver, D.; Cline, M.; Clingenpeel, S.; Collins, B.; Conseil, E.; Corfield, S.; Costello, R.; Costin, R.; Cotton, M.; Craddock, C.; Crosio, M.; Cross, J. A.; Crossland, B.; Crowe, C.; Cruze, S.; Damerell-Moss, R.; Danker, J.; Darcy, M.; David, G.; Dawey, J. M. A.; De A Barreto, V. P.; De Grandis, C.; de Vries, D.; de Witt, S.; Dekker, K.; Delille, S.; Demers, J.; Dether, A.; Devine, K.; Dias, W. A.; Diecks, S.; Dimitrova, E.; Doll, K. M.; Dowden, P.; Duggan, P. N.; Dumitriu, A.; Duncan, L. M.; Dungworth, G.; Dunlea, P.; Dzierwa, D.; Edwards, A.; Elidoro, C.; Ellinger, P.; Elsnau, L. J.; Elustondo, M.; Emery, Y. A.; Evans, H. F.; Evans, J.; Evdokimova, S.; Eve, A.; Fakahany, A.; Farmer, A.; Farrelly, K.; Fazekas, P.; Felsenstein, A.; Fequet, N.; Finney, S.; Fisher, T.; Fletcher, M. S.; Flippo, K.; Fonseca, J. P. B.; Foote, C.; Fox, K.; Fromm, D. C.; Fronczak, S.; Fuchs, R.; Fukushi, H.; Furskog, M.; Gaebel, M.; Gagliano, R.; Gash, D.; Ghegoiu, S.; Gilbert, B.; Gilbertson, J.; Gill, R.; Gillis, A.; Glover, R.; Gonano, V.; Gonzaga, S.; Goodman, S. J.; Gorton, A.; Goznell, L.; Grady, H.; Green, T.; Greutmann, P.; Griffing, C.; Gronowski, P.; Guerreiro, R.; Gutierrez Gomez, E.; Gutler, D.; Guttau, C.; Gwenn, P.; Gyarmati, L.; Hackl, L.; Hager, T.; Hall, E.; Haller, J.; Hantel, T.; Harkin, J.; Harlander, A.; Hartel, C.; Hartmeijer, E.; Harvey, R. F.; Hatwood, A.; Heikes, R.; Heilman, H.; Helk, F.; Helmersen, E.; Hendricks, R.; Hennessey, S.; Hensley, B.; Herentrey, B.; Herr, M.; Herridge, J.; Higgins, J. F.; Hignell, S.; Hodge, T.; Hoffman, T.; Hollerung, T.; Horvath, T.; Hrdlicka, D.; Huefner, M.; Huerta-Martin, A. E.; Hughes, P.; Hui, M. -T.; Hunt, C.; Hutchinson, C.; Ihle, N.; Imp, B.; Ivanchenko, S.; Izakovic, K.; Jackson, P.; Jammer, W.; Jamulla, J. D.; Janssen, N.; Jaureguiberry, A.; Jaworski, D.; Jennings, P.; Jewell, R.; Johnson, W.; Jones, L. F.; Kaczmarek, S. L.; Kaczmarowski, A.; Kaluzny, M.; Kaminski, N.; Kamp, M.; Kanegae, K.; Karge, S.; Karl, A.; Karthikeyan, D.; Kastengren, A.; Kavalli, S.; Kaylor, N.; Kelly, B.; Kendall, C.; Kennedy, A.; Kerr, B.; Kidner, S.; Kidulich, M.; King, R.; Kirschenmann, B.; Klouwen, J. H.; Klug, K.; Koester, K.; Kolling, M.; Korber, R.; Kostrzewa, P.; Kracht, R.; Krawczyk, H.; Krikken, R.; Krol, P.; Kumar, H.; Kumrucu-Lohmiller, M.; Kyriakides, P.; Lactin, D. J.; Lamperti, A.; Lander, J.; Larson, M.; Laurentiu, F.; Le Garff, C.; Le Gendre, P.; Le Tourneau, K.; Ledin, P.; Leegwater, D. V.; Lenke, N.; Leon, P. A.; Levin, A. V.; Lindberg, D.; Lipinski, J.; Lloyd, C.; Loeffler, V. P., III; Lopez-Fabrega, R.; Luchinat, E.; Luers, S.; Lummus, J.; Lunn, P. J.; Lysiak, A.; Macmillan, C.; Macumber, A.; Madala, R.; Madsen, K. L. P.; Magee, S.; Maherjinqiu, R.; Mangili, C.; Mankevich, A.; Manning, B.; Marion, D.; Martin, A.; Martinez, D.; Martins, J. A.; Massuda, M. H.; Matter, B.; Mays, C.; Mazouzi, I.; Mazowiecka, K.; Mazzucato, M. T.; McClure, R.; McDaniel, B.; McGarry, P.; McKee, G. D.; McMillan, D.; Mellor, R.; Mellors, P.; Merc, J.; Mercer, S.; Miller, K.; Mimeev, A.; Mitchell, G.; Moe, J. L.; Mohr, G.; Molders, B. B.; Moldoveanu, R. M.; Moody, E.; Mooney, C.; Moreno-Martinez, C.; Morford, C.; Morgan, A.; Morrill, K.; Mottino, V.; Moyant, B.; Muehlisch, W.; Muller, E.; Myllymaki, T.; Napier, S.; Naujok, J.; Neely, C.; Negus, M.; Nelson, D.; Nembrini, S.; Nethercott, J.; Newgrosh, B.; Newman, C.; Nica, O.; Nicholson, J.; Nissinen, M.; Nordnes, J.; Norris, A. G.; North, O.; Nuber, K.; Nuta, M. -C.; O'Callaghan, G.; Oikkonen, A.; Olejarski, R.; Orsval, R.; Ostler, J.; Ozga, K.; Paklin, N. N.; Pandey, A.; Pani, M.; Pantoni, P.; Pearsall, E. R.; Pedersen, J. K.; Peixoto, J.; Pemberton, S.; Perello, C.; Perlmutter, P. R. G.; Perozzi, E.; Perry, B.; Pettitt, D.; Phillips, M.; Pidgley, K.; Piekarska, N.; Pierce, R.; Piroddu, F.; Playle, T.; Plewinska, M.; Poffel, L.; Pogrebenko, S.; Pollard, T.; Poole, C. W.; Post, A.; Preston, D. L. M.; Pulokas, T.; Purontakanen, J.; Pusch, E.; Pyne, S.; Quinn, J.; Quiroga-Rodriguez, E.; Raab, H.; Radford, C. A.; Rahimi, V. M.; Ravasi, C. E.; Regan, I.; Reisch, F.; Renz, M.; Replogle, B.; Richmond, J.; Rike, E.; Ringsak, Q.; Ringwald, F.; Rojas, A. E. M.; Ronsen, J. P.; Roovers, K.; Ros, J.; Rossman, J.; Roubroeks, S. L.; Rounds, T.; Roynon, G.; Ruedinger, C.; Ruh, M.; Rutledge, N.; Salinas, G. F.; Sanislav, O.; Sankala, H.; Saracino, L.; Savels, M.; Sayle, J. A.; Schafer, T.; Scheuss, U.; Schindler, M.; Schmalz, S.; Schmida, K.; Scholze, T.; Schulz, P.; Schupper, L.; Scott, J.; Scott, M.; Sejpka, J.; Selig, G.; Shaw, B. M.; Shearwater, G.; Sheldon, L.; Shelton, J.; Sheppard, A.; Shirvanian, A.; Shockley, M.; Siddall, K. L.; Sijens, M. J.; Silva, P.; Simister, D. J.; Simmons, M.; Skillman, D.; Slivka, R.; Smith, I. A.; Smith, M.; Smith, R.; Snyder, J.; Sobczuk, B.; Somsikova, L. L.; Souders, M.; Spanjaard, M.; Springer, A.; Stallone, T.; Stano, M.; Stelter, D.; Stephan, R. W.; Stevens, R.; Stewart, P. D.; Stoca, A. D.; Stuart, J.; Sue, J.; Summerlin, P. S.; Taylor, S. R.; Tepper, M.; Tertnes, R.; Thebarge, J.; Thomaidis, P.; Thornton, J.; Tomic, D.; Tompkins, J.; Tormanen, T.; Torsa, A.; Triltzsch, G.; Truog, D., II; Tukendorf, D.; Turaev, T.; Uhl, I.; Unger, C.; van Boven, C.; Van Der Hilst, R.; Van Grijfland, P.; Veillette, M.; Velthuis, R. H. B.; Verdelis, P.; Verga, M.; Verhoeven, G.; Vertinskis, A.; Vigil, P.; Volkel, D.; Vorley, T.; Vorobjov, T.; Vorochilov, V.; Wah, L. L. W.; Walravens, E.; Ward, D.; Ward, S.; Warner, J. D.; Wartenberg, J.; Washbourn, G.; Waterfield, P.; Wegert, S.; Wegner-Kaminski, A.; Weilant, D.; Westbrook, D.; Wheat, J.; Wheeldon, N.; Whitfield, D.; Wille, A.; Winkle, M. V.; Wollenhaupt, G.; Woodhams, D.; Wrobel, A.; Yandle, C.; Zeddam, J.; Zeigler, D. R.; Zinke, L.; Zinn, B.; Zormpa, I.; Mas, J. G.; Williams, G. V. Bibcode: 2012MPEC....F..109F Altcode: No abstract at ADS Title: VizieR Online Data Catalog: The Magellanic Mopra Assessment (MAGMA). I. (Wong+, 2011) Authors: Wong, T.; Hughes, A.; Ott, J.; Muller, E.; Pineda, J. L.; Bernard, J. -P.; Chu, Y. -H.; Fukui, Y.; Gruendl, R. A.; Henkel, C.; Kawamura, A.; Klein, U.; Looney, L. W.; Maddison, S.; Mizuno, Y.; Paradis, D.; Seale, J.; Daniel, E. W. Bibcode: 2012yCat..21970016W Altcode: Observations were performed with the Australia Telescope National Facility (ATNF) Mopra 22m telescope from 2005 May to 2010 October.

(3 data files). Title: Parametrized 3D models of neutrino-driven supernova explosions. Neutrino emission asymmetries and gravitational-wave signals Authors: Müller, E.; Janka, H. -Th.; Wongwathanarat, A. Bibcode: 2012A&A...537A..63M Altcode: 2011arXiv1106.6301M Time-dependent and direction-dependent neutrino and gravitational-wave (GW) signatures are presented for a set of three-dimensional (3D) hydrodynamic models of parametrized, neutrino-driven supernova explosions of non-rotating 15 and 20 M stars. We employed an approximate treatment of neutrino transport based on a gray spectral description and a ray-by-ray treatment of multi-dimensional effects. Owing to the excision of the high-density core of the proto-neutron star (PNS) and the use of an axis-free (Yin-Yang) overset grid, the models can be followed from the post-bounce accretion phase through the onset of the explosion into more than one second of the early cooling evolution of the PNS without imposing any symmetry restrictions and covering a full sphere. Gravitational waves and neutrino emission exhibit the generic time-dependent features already known from 2D (axi-symmetric) models. Violent non-radial hydrodynamic mass motions in the accretion layer and their interaction with the outer layers of the proto-neutron star together with anisotropic neutrino emission give rise to a GW signal with an amplitude of ~5-20 cm in the frequency range of 100-500 Hz. The GW emission from mass motions usually reaches a maximum before the explosion sets in. After the onset of the explosion the GW signal exhibits a low-frequency modulation, in some cases describing a quasi-monotonic growth, associated with the non-spherical expansion of the explosion shock wave and the large-scale anisotropy of the escaping neutrino flow. Variations of the mass-quadrupole moment caused by convective activity inside the nascent neutron star add a high-frequency component to the GW signal during the post-explosion phase. The GW signals exhibit strong variability between the two polarizations, different explosion simulations and different observer directions, and besides common basic features do not possess any template character. The neutrino emission properties (fluxes and effective spectral temperatures) show fluctuations over the neutron star surface on spatial and temporal scales that reflect the different types of non-spherical mass motions in the supernova core, i.e., post-shock overturn flows and proto-neutron star convection. However, because very prominent, quasi-periodic sloshing motions of the shock caused by the standing accretion-shock instability are absent and the emission from different surface areas facing an observer adds up incoherently, the modulation amplitudes of the measurable neutrino luminosities and mean energies are significantly lower than predicted by 2D simulations. Title: A New Stellar Mixing Process Operating below Shell Convection Zones Following Off-center Ignition Authors: Mocák, M.; Meakin, Casey A.; Müller, E.; Siess, L. Bibcode: 2011ApJ...743...55M Altcode: 2011arXiv1108.4433M During most stages of stellar evolution the nuclear burning of lighter to heavier elements results in a radial composition profile which is stabilizing against buoyant acceleration, with light material residing above heavier material. However, under some circumstances, such as off-center ignition, the composition profile resulting from nuclear burning can be destabilizing and characterized by an outwardly increasing mean molecular weight. The potential for instabilities under these circumstances and the consequences that they may have on stellar structural evolution remain largely unexplored. In this paper we study the development and evolution of instabilities associated with unstable composition gradients in regions that are initially stable according to linear Schwarzschild and Ledoux criteria. In particular, we study the development of turbulent flow under a variety of stellar evolution conditions with multi-dimensional hydrodynamic simulation; the phases studied include the core helium flash in a 1.25 M star, the core carbon flash in a 9.3 M star, and oxygen shell burning in a 23 M star. The results of our simulations reveal a mixing process associated with regions having outwardly increasing mean molecular weight that reside below convection zones. The mixing is not due to overshooting from the convection zone, nor is it due directly to thermohaline mixing which operates on a timescale several orders of magnitude larger than the simulated flows. Instead, the mixing appears to be due to the presence of a wave field induced in the stable layers residing beneath the convection zone which enhances the mixing rate by many orders of magnitude and allows a thermohaline type mixing process to operate on a dynamical, rather than thermal, timescale. The mixing manifests itself in the form of overdense and cold blob-like structures originating from density fluctuations at the lower boundary of convective shell and "shooting" down into the core. They are enriched with nuclearly processed material, hence leaving behind traces of higher mean molecular weight. In these regions, we find that initially smooth composition gradients steepen into stair-step-like profiles in which homogeneous, mixed regions are separated by composition jumps. These step-like profiles are then seen to evolve by a process of interface migration driven by turbulent entrainment. We discuss our results in terms of related laboratory phenomena and associated theoretical developments. We also discuss the degree to which the simulated mixing rates depend on the numerical resolution, and what future steps can be taken to capture the mixing rates accurately. Title: Surveying the Agents of Galaxy Evolution in the Tidally Stripped, Low Metallicity Small Magellanic Cloud (SAGE-SMC). I. Overview Authors: Gordon, K. D.; Meixner, M.; Meade, M. R.; Whitney, B.; Engelbracht, C.; Bot, C.; Boyer, M. L.; Lawton, B.; Sewiło, M.; Babler, B.; Bernard, J. -P.; Bracker, S.; Block, M.; Blum, R.; Bolatto, A.; Bonanos, A.; Harris, J.; Hora, J. L.; Indebetouw, R.; Misselt, K.; Reach, W.; Shiao, B.; Tielens, X.; Carlson, L.; Churchwell, E.; Clayton, G. C.; Chen, C. -H. R.; Cohen, M.; Fukui, Y.; Gorjian, V.; Hony, S.; Israel, F. P.; Kawamura, A.; Kemper, F.; Leroy, A.; Li, A.; Madden, S.; Marble, A. R.; McDonald, I.; Mizuno, A.; Mizuno, N.; Muller, E.; Oliveira, J. M.; Olsen, K.; Onishi, T.; Paladini, R.; Paradis, D.; Points, S.; Robitaille, T.; Rubin, D.; Sandstrom, K.; Sato, S.; Shibai, H.; Simon, J. D.; Smith, L. J.; Srinivasan, S.; Vijh, U.; Van Dyk, S.; van Loon, J. Th.; Zaritsky, D. Bibcode: 2011AJ....142..102G Altcode: 2011arXiv1107.4313G The Small Magellanic Cloud (SMC) provides a unique laboratory for the study of the lifecycle of dust given its low metallicity (~1/5 solar) and relative proximity (~60 kpc). This motivated the SAGE-SMC (Surveying the Agents of Galaxy Evolution in the Tidally Stripped, Low Metallicity Small Magellanic Cloud) Spitzer Legacy program with the specific goals of studying the amount and type of dust in the present interstellar medium, the sources of dust in the winds of evolved stars, and how much dust is consumed in star formation. This program mapped the full SMC (30 deg2) including the body, wing, and tail in seven bands from 3.6 to 160 μm using IRAC and MIPS on the Spitzer Space Telescope. The data were reduced and mosaicked, and the point sources were measured using customized routines specific for large surveys. We have made the resulting mosaics and point-source catalogs available to the community. The infrared colors of the SMC are compared to those of other nearby galaxies and the 8 μm/24 μm ratio is somewhat lower than the average and the 70 μm/160 μm ratio is somewhat higher than the average. The global infrared spectral energy distribution (SED) shows that the SMC has approximately 1/3 the aromatic emission/polycyclic aromatic hydrocarbon abundance of most nearby galaxies. Infrared color-magnitude diagrams are given illustrating the distribution of different asymptotic giant branch stars and the locations of young stellar objects. Finally, the average SED of H II/star formation regions is compared to the equivalent Large Magellanic Cloud average H II/star formation region SED. These preliminary results will be expanded in detail in subsequent papers. Title: Multidimensional hydrodynamic simulations of the hydrogen injection flash Authors: Mocák, M.; Siess, L.; Müller, E. Bibcode: 2011A&A...533A..53M Altcode: 2011arXiv1106.3260M Context. The injection of hydrogen into the convection shell powered by helium burning during the core helium flash is commonly encountered during the evolution of metal-free and extremely metal-poor low-mass stars. Multidimensional hydrodynamic simulations indicate that the hydrogen injection may also occur in more metal-rich stars due to turbulent entrainment that accelerates the growth of the shell convection zone and increases its size. However, one-dimensional stellar models cast doubts that helium-flash hydrogen mixing does occur as it requires the crossing of an entropy barrier at the helium-hydrogen interface.
Aims: With specifically designed multidimensional hydrodynamic simulations, we aim to prove that an entropy barrier is no obstacle to the growth of the helium-burning shell convection zone in the helium core of a metal-rich Population I star, i.e. convection can penetrate into the hydrogen-rich layers for these stars, too. We study whether this is also possible in one-dimensional stellar evolutionary calculations.
Methods: We artificially shift the hydrogen-rich layer closer to the outer edge of the helium-burning shell convection zone in a Population I star with a mass of 1.25 M, and simulate the subsequent evolution in two and three dimensions, respectively. We also perform stellar evolutionary calculations of the core helium flash in metal-rich stars implementing turbulent entrainment by means of a simple prescription. These simulations were performed with the Eulerian hydrodynamical code HERAKLES and the stellar evolution code STAREVOL, respectively.
Results: Our hydrodynamical simulations show that the helium-burning shell convection zone in the helium core moves across the entropy barrier and reaches the hydrogen-rich layers. This leads to a mixing of protons into the hotter layers of the core and to a rapid increase in the nuclear energy production at the upper edge of the helium-burning convection shell - the hydrogen injection flash. As a result, a second convection zone appears in the hydrogen-rich layers. In contrast to one-dimensional models, the entropy barrier separating the two convective shells from each other is largely permeable to chemical transport when allowing for multidimensional flow and consequently hydrogen is continuously mixed deep into the helium core. We find it difficult to replicate this behavior using one-dimensional stellar evolutionary calculations. Title: Influence of thermonuclear effects on the collapse of supermassive stars Authors: Montero, Pedro J.; Janka, H. -T.; Müller, E.; Müller, B. Bibcode: 2011JPhCS.314a2077M Altcode: We present results of general relativistic simulations of collapsing supermassive stars using the two-dimensional general relativistic numerical code Nada, which solves the Einstein equations written in the BSSN formalism and the general relativistic hydrodynamic equations with high resolution shock capturing schemes. These numerical simulations use a tabulated equation of state which includes effects of radiation and gas pressure, and those associated with the electron-positron pairs. We also take into account the effect of thermonuclear energy released by hydrogen and helium burning. We find that objects with mass ≈ 5 × 105M and initial metallicity greater than ZCNO ≈ 0.004 do explode if non-rotating, while the threshold metallicity for an explosion is reduced to ZCNO ≈ 0.002 for objects uniformly rotating. Title: Hydromagnetic instabilities and magnetic field amplification in core collapse supernovae Authors: Cerdá-Durán, P.; Obergaulinger, M.; Aloy, M. A.; Font, J. A.; Müller, E. Bibcode: 2011JPhCS.314a2079C Altcode: Some of the most violent events in the universe, the gamma ray burst, could be related to the gravitational collapse of massive stellar cores. The recent association of long GRBs to some class of type Ic supernova seems to support this view. In such scenario fast rotation, strong magnetic fields and general relativistic effects are key ingredients. It is thus important to understand the mechanism that amplifies the magnetic field under that conditions. I present global simulations of the magneto-rotational collapse of stellar cores in general relativity and semi-global simulations of hydromagnetic instabilities under core collapse conditions. I discuss effect of the magneto-rotational instability and the magnetic field amplification during the collapse, the uncertainties in this process and the dynamical effects in the supernova explosion. Title: High-order methods for the simulation of hydromagnetic instabilities in core-collapse supernovae Authors: Rembiasz, T.; Obergaulinger, M.; Aloy, M. Angel; Cerdá-Durán, P.; Müller, E. Bibcode: 2011IAUS..274..479R Altcode: We present an assessment of the accuracy of a recently developed MHD code used to study hydromagnetic flows in supernovae and related events. The code, based on the constrained transport formulation, incorporates unprecedented ultra-high-order methods (up to 9th order) for the reconstruction and the most accurate approximate Riemann solvers. We estimate the numerical resistivity of these schemes in tearing instability simulations. Title: The CO Isotope Ratio of the Large Magellanic Cloud Authors: Wyss, Sarah; Ott, J.; Meier, D.; Wong, T.; Hughes, A.; Pineda, J.; Muller, E. Bibcode: 2011AAS...21725126W Altcode: 2011BAAS...4325126W Giant molecular clouds (GMCs) are the home of star formation, yet are difficult to observe and thus their physical characteristics remain largely unknown. The proximity, size, inclination and star-forming properties of the Large Magellanic Cloud (LMC, distance 50kpc) present a perfect opportunity for a comprehensive, high-spectral-resolution and high-spatial-resolution survey of these clouds. Using the 12CO (1-0) and 13CO (1-0) Magellanic Mopra Assessment (MAGMA) data, we study over 155 giant molecular clouds distributed throughout the LMC at 8pc resolution. The 13CO (1-0) transition is detected at or above the level of significance in all clouds examined. The intensity ratio of the 13CO (1-0) to 12CO (1-0) transitions is found to be highly uniform across the LMC, not varying strongly with GMC evolutionary state, galactocentric regions, star formation rate or interaction with the Milky Way. We discover an unexplained correlation between 12CO average brightness temperature and the isotope intensity ratio. We produce galaxy-wide spectra in 12CO (1-0) and 13CO (1-0) and examine the galaxy-wide 13CO (1-0) to 12CO (1-0) ratio, simulating observations of similar, more distant galaxies. Comparison of this ratio with the ratio measured locally from individual clouds yields an overall 13CO (1-0) filling factor of 0.3 of 12CO(1-0). Title: Spitzer View of Massive Star Formation at Reduced Metallicity Environment Authors: Chen, C. H. Rosie; Indebetouw, R.; Chu, Y.; Gruendl, R.; Muller, E.; Fukui, Y.; Kawamura, A.; Testor, G.; Gordon, K.; Heitsch, F.; Leroy, A.; Meixner, M.; Seale, J.; Sewilo, M.; Sloan, G.; Whitney, B.; SAGE Team Bibcode: 2011AAS...21725828C Altcode: 2011BAAS...4325828C Recent Spitzer mid-IR observations have revealed a large number of individually resolved massive young stellar objects (YSOs) in the Magellanic clouds, providing an excellent opportunity to study massive star formation with metallicity and galactic environment different from the Milky Way. Using Spitzer IRAC/MIPS data from SAGE survey and complementary high-resolution ground-based optical/near-IR data, we have identified YSOs in HII complexes in the Large and Small Magellanic Cloud (LMC and SMC) and a large area in the Magellanic Bridge. These systems span a metallicity range of 1/3-1/8 Zo, and different galactic environments with star formation modes from mainly self-propagating in the LMC to tidally disrupted in the Bridge. We have modeled spectral energy distributions of the YSOs and found that they have masses ranging from 4 to 45 Mo in the LMC and SMC, while the most massive ones in the Bridge are < 10 Mo. YSOs in these three systems are found to span a wide range of evolutionary stages from highly embedded to surrounded by remnant material, though for the same mass range YSOs in the Bridge appear less embedded as almost all of them are visible at optical, opposed to only a small fraction in the LMC. The smaller extinction may be due to Bridge's lower dust content in either the CO clouds or circumstellar envelopes, or both. Using surveys in Hα, CO, and HI of these three systems, we further investigate the causal relationship between gas and stars. Examination of individual regions shows that massive YSOs tend to be found near ionized gas, i.e., where massive stars formed a few Myr ago, and the correlation is strongest for O-type YSOs. It appears that energy feedback plays a significant role in massive star formation. Star formation efficiencies in regions in these three systems are comparable, < 1/100-1/1000. Title: The core helium flash revisited. III. From Population I to Population III stars Authors: Mocák, M.; Campbell, S. W.; Müller, E.; Kifonidis, K. Bibcode: 2010A&A...520A.114M Altcode: 2010arXiv1003.3646M Context. Degenerate ignition of helium in low-mass stars at the end of the red giant branch phase leads to dynamic convection in their helium cores. One-dimensional (1D) stellar modeling of this intrinsically multi-dimensional dynamic event is likely to be inadequate. Previous hydrodynamic simulations imply that the single convection zone in the helium core of metal-rich Pop I stars grows during the flash on a dynamic timescale. This may lead to hydrogen injection into the core and to a double convection zone structure as known from one-dimensional core helium flash simulations of low-mass Pop III stars.
Aims: We perform hydrodynamic simulations of the core helium flash in two and three dimensions to better constrain the nature of these events. To this end we study the hydrodynamics of convection within the helium cores of a 1.25 M_⊙ metal-rich Pop I star (Z = 0.02), and, for the first time, a 0.85 M_⊙ metal-free Pop III star (Z = 0) near the peak of the flash. These models possess single and double convection zones, respectively.
Methods: We use 1D stellar models of the core helium flash computed with state-of-the-art stellar evolution codes as initial models for our multidimensional hydrodynamic study, and simulate the evolution of these models with the Riemann solver based hydrodynamics code Herakles, which integrates the Euler equations coupled with source terms corresponding to gravity and nuclear burning.
Results: The hydrodynamic simulation of the Pop I model involving a single convection zone covers 27 h of stellar evolution, while the hydrodynamic simulations of a double convection zone, in the Pop III model, span 1.8 h of stellar life. We find differences between the predictions of mixing length theory and our hydrodynamic simulations. The simulation of the single convection zone in the Pop I model shows a strong growth of the size of the convection zone due to turbulent entrainment. We therefore predict that for the Pop I model a hydrogen injection phase (i.e., hydrogen injection into the helium core) will commence after about 23 days, which should eventually lead to a double convection zone structure known from 1D stellar modeling of low-mass Pop III stars. Our two and three-dimensional hydrodynamic simulations of the double (Pop III) convection zone model show that the velocity field in the convection zones is different from that given by stellar evolutionary calculations. The simulations suggest that the double convection zone decays quickly, the flow eventually being dominated by internal gravity waves. The decay could be an artefact caused by the mapping of the initial stellar model to the numerical grid of our hydrodynamics code. Title: Simulations of the Magneto-rotational Instability in Core-Collapse Supernovae Authors: Obergaulinger, M.; Cerdá-Durán, P.; Müller, E.; Aloy, M. A. Bibcode: 2010ASPC..429..136O Altcode: 2009arXiv0911.3222O We assess the importance of the magneto-rotational instability in core-collapse supernovae by an analysis of the growth rates of unstable modes in typical post-collapse systems and by numerical simulations of simplified models. The interplay of differential rotation and thermal stratification defines different instability regimes which we confirm in our simulations. We investigate the termination of the growth of the MRI by parasitic instabilities, establish scaling laws characterising the termination amplitude, and study the long-term evolution of the saturated turbulent state. Title: Physical properties of giant molecular clouds in the Large Magellanic Cloud Authors: Hughes, A.; Wong, T.; Ott, J.; Muller, E.; Pineda, J. L.; Mizuno, Y.; Bernard, J. -P.; Paradis, D.; Maddison, S.; Reach, W. T.; Staveley-Smith, L.; Kawamura, A.; Meixner, M.; Kim, S.; Onishi, T.; Mizuno, N.; Fukui, Y. Bibcode: 2010MNRAS.406.2065H Altcode: 2010arXiv1004.2094H; 2010MNRAS.tmp..873H The Magellanic Mopra Assessment (MAGMA) is a high angular resolution 12CO (J = 1 -> 0) mapping survey of giant molecular clouds (GMCs) in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud using the Mopra Telescope. Here we report on the basic physical properties of 125 GMCs in the LMC that have been surveyed to date. The observed clouds exhibit scaling relations that are similar to those determined for Galactic GMCs, although LMC clouds have narrower linewidths and lower CO luminosities than Galactic clouds of a similar size. The average mass surface density of the LMC clouds is 50 Msolarpc-2, approximately half that of GMCs in the inner Milky Way. We compare the properties of GMCs with and without signs of massive star formation, finding that non-star-forming GMCs have lower peak CO brightness than star-forming GMCs. We compare the properties of GMCs with estimates for local interstellar conditions: specifically, we investigate the HI column density, radiation field, stellar mass surface density and the external pressure. Very few cloud properties demonstrate a clear dependence on the environment; the exceptions are significant positive correlations between (i) the HI column density and the GMC velocity dispersion, (ii) the stellar mass surface density and the average peak CO brightness and (iii) the stellar mass surface density and the CO surface brightness. The molecular mass surface density of GMCs without signs of massive star formation shows no dependence on the local radiation field, which is inconsistent with the photoionization-regulated star formation theory proposed by McKee. We find some evidence that the mass surface density of the MAGMA clouds increases with the interstellar pressure, as proposed by Elmegreen, but the detailed predictions of this model are not fulfilled once estimates for the local radiation field, metallicity and GMC envelope mass are taken into account. Title: The Arecibo L-band Feed Array Zone of Avoidance Survey. I. Precursor Observations Through the Inner and Outer Galaxy Authors: Henning, P. A.; Springob, C. M.; Minchin, R. F.; Momjian, E.; Catinella, B.; McIntyre, T.; Day, F.; Muller, E.; Koribalski, B.; Rosenberg, J. L.; Schneider, S.; Staveley-Smith, L.; van Driel, W. Bibcode: 2010AJ....139.2130H Altcode: 2010arXiv1002.2933H The Arecibo L-band Feed Array (ALFA) is being used to conduct a low-Galactic latitude survey, to map the distribution of galaxies and large-scale structures behind the Milky Way through detection of galaxies' neutral hydrogen (H I) 21 cm emission. This Zone of Avoidance (ZOA) survey finds new H I galaxies which lie hidden behind the Milky Way, and also provides redshifts for partially obscured galaxies known at other wavelengths. Before the commencement of the full survey, two low-latitude precursor regions were observed, totaling 138 deg2, with 72 H I galaxies detected. Detections through the inner Galaxy generally have no cataloged counterparts in any other waveband, due to the heavy extinction and stellar confusion. Detections through the outer Galaxy are more likely to have Two Micron All Sky Survey counterparts. We present the results of these precursor observations, including a catalog of the detected galaxies, with their H I parameters. The survey sensitivity is well described by a flux- and linewidth-dependent signal-to-noise ratio of 6.5. ALFA ZOA galaxies, which also have H I measurements in the literature, show good agreement between our measurements and previous work. The inner Galaxy precursor region was chosen to overlap the H I Parkes Zone of Avoidance Survey, so ALFA performance could be quickly assessed. The outer Galaxy precursor region lies north of the Parkes sky. Low-latitude large-scale structure in this region is revealed, including an overdensity of galaxies near ell = 183° and between 5000-6000 km s-1 in the ZOA. The full ALFA ZOA survey will be conducted in two phases: a shallow survey using the observing techniques of the precursor observations, and also a deep phase with much longer integration time, with thousands of galaxies predicted for the final catalog. Title: Local simulations of the magnetized Kelvin-Helmholtz instability in neutron-star mergers Authors: Obergaulinger, M.; Aloy, M. A.; Müller, E. Bibcode: 2010A&A...515A..30O Altcode: 2010arXiv1003.6031O Context. Global magnetohydrodynamic simulations show the growth of Kelvin-Helmholtz instabilities at the contact surface of two merging neutron stars. That region has been identified as the site of efficient amplification of magnetic fields. However, these global simulations, due to numerical limitations, were unable to determine the saturation level of the field strength, and thus the possible back-reaction of the magnetic field onto the flow.
Aims: We investigate the amplification of initially weak magnetic fields in Kelvin-Helmholtz unstable shear flows, and the back-reaction of the field onto the flow.
Methods: We use a high-resolution finite-volume ideal MHD code to perform 2D and 3D local simulations of hydromagnetic shear flows, both for idealized systems and simplified models of merger flows.
Results: In 2D, the magnetic field is amplified on time scales of less than 0.01 ms until it reaches locally equipartition with the kinetic energy. Subsequently, it saturates due to resistive instabilities that disrupt the Kelvin-Helmholtz unstable vortex and decelerate the shear flow on a secular time scale. We determine scaling laws of the field amplification with the initial field strength and the grid resolution. In 3D, the hydromagnetic mechanism seen in 2D may be dominated by purely hydrodynamic instabilities leading to less filed amplification. We find maximum magnetic fields ~1016 G locally, and rms maxima within the box ~1015 G. However, due to the fast decay of the shear flow such strong fields exist only for a short period (<0.1 ms). In the saturated state of most models, the magnetic field is mainly oriented parallel to the shear flow for rather strong initial fields, while weaker initial fields tend to lead to a more balanced distribution of the field energy among the components. In all models the flow shows small-scale features. The magnetic field is at most in energetic equipartition with the decaying shear flow.
Conclusions: The magnetic field may be amplified efficiently to very high field strengths, the maximum field energy reaching values of the order of the kinetic energy associated with the velocity components transverse to the interface between the two neutron stars. However, the dynamic impact of the field onto the flow is limited to the shear layer, and it may not be adequate to produce outflows, because the time during which the magnetic field stays close to its maximum value is short compared to the time scale for launching an outflow (i.e., a few milliseconds). Title: An axis-free overset grid in spherical polar coordinates for simulating 3D self-gravitating flows Authors: Wongwathanarat, A.; Hammer, N. J.; Müller, E. Bibcode: 2010A&A...514A..48W Altcode: 2010arXiv1003.1633W
Aims: Three dimensional explicit hydrodynamic codes based on spherical polar coordinates using a single spherical polar grid suffer from a severe restriction of the time step size due to the convergence of grid lines near the poles of the coordinate system. More importantly, numerical artifacts are encountered at the symmetry axis of the grid where boundary conditions have to be imposed that flaw the flow near the axis. The first problem can be eased and the second one avoided by applying an overlapping grid technique.
Methods: A type of overlapping grid in spherical coordinates is adopted. This so called “Yin-Yang” grid is a two-patch overset grid proposed by Kageyama and Sato for geophysical simulations. Its two grid patches contain only the low-latitude regions of the usual spherical polar grid and are combined together in a simple manner. This property of the Yin-Yang grid greatly simplifies its implementation into a 3D code already employing spherical polar coordinates. It further allows for a much larger time step in 3D simulations using high angular resolution (⪉1°) than that required in 3D simulations using a regular spherical grid with the same angular resolution.
Results: The Yin-Yang grid is successfully implemented into a 3D version of the explicit Eulerian grid-based code PROMETHEUS including self-gravity. The modified code successfully passed several standard hydrodynamic tests producing results which are in very good agreement with analytic solutions. Moreover, the solutions obtained with the Yin-Yang grid exhibit no peculiar behaviour at the boundary between the two grid patches. The code has also been successfully used to model astrophysically relevant situations, namely equilibrium polytropes, a Taylor-Sedov explosion, and Rayleigh-Taylor instabilities. According to our results, the usage of the Yin-Yang grid greatly enhances the suitability and efficiency of 3D explicit Eulerian codes based on spherical polar coordinates for astrophysical flows. Title: Three-dimensional Simulations of Mixing Instabilities in Supernova Explosions Authors: Hammer, N. J.; Janka, H. -Th.; Müller, E. Bibcode: 2010ApJ...714.1371H Altcode: 2009arXiv0908.3474H We present the first three-dimensional (3D) simulations of the large-scale mixing that takes place in the shock-heated stellar layers ejected in the explosion of a 15.5 M sun blue supergiant star. The blast is initiated and powered by neutrino-energy deposition behind the stalled shock by means of choosing sufficiently high neutrino luminosities from the contracting, nascent neutron star, whose high-density core is excised and replaced by a retreating inner grid boundary. The outgoing supernova shock is followed beyond its breakout from the stellar surface more than 2 hr after the core collapse. Violent convective overturn in the post-shock layer causes the explosion to start with significant large-scale asphericity, which acts as a trigger of the growth of Rayleigh-Taylor instabilities at the composition interfaces of the exploding star. Despite the absence of a strong Richtmyer-Meshkov instability at the H/He interface, which only a largely deformed shock could instigate, deep inward mixing of hydrogen is found as well as fast-moving, metal-rich clumps penetrating with high velocities far into the hydrogen envelope of the star as observed, for example, in the case of Supernova 1987A. Also individual clumps containing a sizeable fraction of the ejected iron-group elements (up to several 10-3 M sun) are obtained in some models. The metal core of the progenitor is partially turned over with nickel-dominated fingers overtaking oxygen-rich bullets and both nickel and oxygen moving well ahead of the material from the carbon layer. Comparing with corresponding two-dimensional (axially symmetric; 2D) calculations, we determine the growth of the Rayleigh-Taylor fingers to be faster, the deceleration of the dense metal-carrying clumps in the helium and hydrogen layers to be reduced, the asymptotic clump velocities in the hydrogen shell to be higher (up to ~4500 km s-1 for the considered progenitor and an explosion energy of 1051 erg, instead of lsim2000 km s-1 in 2D), and the outward radial mixing of heavy elements and inward mixing of hydrogen to be more efficient in 3D than in 2D. We present a simple argument that explains these results as a consequence of the different action of drag forces on moving objects in the two geometries. Title: Characterizing the Low-Mass Molecular Component in the Northern Small Magellanic Cloud Authors: Muller, E.; Ott, J.; Hughes, A.; Pineda, J. L.; Wong, T.; Mizuno, N.; Kawamura, A.; Mizuno, Y.; Fukui, Y.; Onishi, T.; Rubio, M. Bibcode: 2010ApJ...712.1248M Altcode: 2010arXiv1001.4757M We present here the first results from a high-resolution survey of the 12CO(J = 1-0) emission across the northern part of the poorly enriched Small Magellanic Cloud (SMC), made with the ATNF Mopra telescope. Three molecular complexes detected in the lower resolution NANTEN survey are mapped with a beam FWHM of ~42'', to sensitivities of approximately 210 mK per 0.9 km s-1 channel, resolving each complex into 4-7 small clouds of masses in the range of M vir ~ 103-104 M sun and with radii no larger than 16 pc. The northern SMC CO clouds follow similar empirical relationships to the southern SMC population, yet they appear relatively under-luminous for their size, suggesting that the star-forming environment in the SMC is not homogeneous. Our data also suggests that the CO cloud population has little or no extended CO envelope on scales gsim30 pc, further evidence that the weak CO component in the north SMC is being disassociated by penetrating UV radiation. The new high-resolution data provide evidence for a variable correlation of the CO integrated brightness with integrated H I and 160 μm emission; in particular CO is often, but not always, found coincident with peaks of 160 μm emission, verifying the need for matching-resolution 160 μm and H I data for a complete assessment of the SMC H2 mass. Title: Molecular and Atomic Gas in the Large Magellanic Cloud. II. Three-dimensional Correlation Between CO and H I Authors: Fukui, Y.; Kawamura, A.; Wong, T.; Murai, M.; Iritani, H.; Mizuno, N.; Mizuno, Y.; Onishi, T.; Hughes, A.; Ott, J.; Muller, E.; Staveley-Smith, L.; Kim, S. Bibcode: 2009ApJ...705..144F Altcode: 2009arXiv0909.0382F We compare the CO (J = 1-0) and H I emission in the Large Magellanic Cloud in three dimensions, i.e., including a velocity axis in addition to the two spatial axes, with the aim of elucidating the physical connection between giant molecular clouds (GMCs) and their surrounding H I gas. The CO J = 1-0 data set is from the second NANTEN CO survey and the H I data set is from the merged Australia Telescope Compact Array (ATCA) and Parkes Telescope surveys. The major findings of our analysis are as follows: (1) GMCs are associated with an envelope of H I emission, (2) in GMCs [average CO intensity] vprop [average H I intensity]1.1±0.1, and (3) the H I intensity tends to increase with the star formation activity within GMCs, from Type I to Type III. An analysis of the H I envelopes associated with GMCs shows that their average line width is 14 km s-1 and the mean density in the envelope is 10 cm-3. We argue that the H I envelopes are gravitationally bound by GMCs. These findings are consistent with a continual increase in the mass of GMCs via H I accretion at an accretion rate of 0.05 M sun yr-1 over a timescale of 10 Myr. The growth of GMCs is terminated via dissipative ionization and/or stellar-wind disruption in the final stage of GMC evolution. Title: The core helium flash revisited. II. Two and three-dimensional hydrodynamic simulations Authors: Mocák, M.; Müller, E.; Weiss, A.; Kifonidis, K. Bibcode: 2009A&A...501..659M Altcode: 2008arXiv0811.4083M Context: We study turbulent convection during the core helium flash close to its peak by comparing the results of two and three-dimensional hydrodynamic simulations.
Aims: In a previous study we found that the temporal evolution and the properties of the convection inferred from two-dimensional hydrodynamic studies are similar to those predicted by quasi-hydrostatic stellar evolutionary calculations. However, as vorticity is conserved in axisymmetric flows, two-dimensional simulations of convection are characterized by incorrect dominant spatial scales and exaggerated velocities. Here, we present three-dimensional simulations that eliminate the restrictions and flaws of two-dimensional models and that provide a geometrically unbiased insight into the hydrodynamics of the core helium flash. In particular, we study whether the assumptions and predictions of stellar evolutionary calculations based on the mixing-length theory can be confirmed by hydrodynamic simulations.
Methods: We used a multidimensional Eulerian hydrodynamics code based on state-of-the-art numerical techniques to simulate the evolution of the helium core of a 1.25 M Pop I star.
Results: Our three-dimensional hydrodynamic simulations of the evolution of a star during the peak of the core helium flash do not show any explosive behavior. The convective flow patterns developing in the three-dimensional models are structurally different from those of the corresponding two-dimensional models, and the typical convective velocities are lower than those found in their two-dimensional counterparts. Three-dimensional models also tend to agree more closely with the predictions of mixing length theory. Our hydrodynamic simulations show the turbulent entrainment that leads to a growth of the convection zone on a dynamic time scale. In contrast to mixing length theory, the outer part of the convection zone is characterized by a subadiabatic temperature gradient. Title: Molecular and Atomic Gas in the Large Magellanic Cloud. I. Conditions for CO Detection Authors: Wong, T.; Hughes, A.; Fukui, Y.; Kawamura, A.; Mizuno, N.; Ott, J.; Muller, E.; Pineda, J. L.; Welty, D. E.; Kim, S.; Mizuno, Y.; Murai, M.; Onishi, T. Bibcode: 2009ApJ...696..370W Altcode: 2009arXiv0902.1578W We analyze the conditions for detection of CO(1-0) emission in the Large Magellanic Cloud, using the recently completed second NANTEN CO survey. In particular, we investigate correlations between CO integrated intensity and H I integrated intensity, peak brightness temperature, and line width at a resolution of 2farcm6 (~40 pc). We find that significant H I column density (exceeding ~1021 cm-2) and peak brightness temperature (exceeding ~20 K) are necessary but not sufficient conditions for CO detection, with many regions of strong H I emission not associated with molecular clouds. The large scatter in CO intensities for a given H I intensity persists even when averaging on scales of >200 pc, indicating that the scatter is not solely due to local conversion of H I into H2 near GMCs. We focus on two possibilities to account for this scatter: either there exist spatial variations in the I(CO) to N(H2) conversion factor, or a significant fraction of the atomic gas is not involved in molecular cloud formation. A weak tendency for CO emission to be suppressed for large H I linewidths supports the second hypothesis, insofar as large linewidths may be indicative of warm H I, and calls into question the likelihood of forming molecular clouds from colliding H I flows. We also find that the ratio of molecular to atomic gas shows no significant correlation (or anticorrelation) with the stellar surface density, though a correlation with midplane hydrostatic pressure Ph is found when the data are binned in Ph . The latter correlation largely reflects the increasing likelihood of CO detection at high H I column density. Title: Molecular line mapping of the giant molecular cloud associated with RCW 106 - III. Multimolecular line mapping Authors: Lo, N.; Cunningham, M. R.; Jones, P. A.; Bains, I.; Burton, M. G.; Wong, T.; Muller, E.; Kramer, C.; Ossenkopf, V.; Henkel, C.; Deragopian, G.; Donnelly, S.; Ladd, E. F. Bibcode: 2009MNRAS.395.1021L Altcode: 2009arXiv0902.2452L; 2009MNRAS.tmp..403L We present multimolecular line maps obtained with the Mopra telescope towards the southern giant molecular cloud (GMC) complex G333, associated with the H ii region RCW 106. We have characterized the GMC by decomposing the 3D data cubes with gaussclumps, and investigated spatial correlations among different molecules with principal component analysis (PCA). We find no correlation between clump size and linewidth, but a strong correlation between emission luminosity and linewidth. PCA classifies molecules into high- and low-density tracers, and reveals that HCO+ and N2H+ are anticorrelated. Title: Semi-global simulations of the magneto-rotational instability in core collapse supernovae Authors: Obergaulinger, M.; Cerdá-Durán, P.; Müller, E.; Aloy, M. A. Bibcode: 2009A&A...498..241O Altcode: 2008arXiv0811.1652O Context: Possible effects of magnetic fields in core collapse supernovae rely on an efficient amplification of the weak pre-collapse fields. It has been suggested that the magneto-rotational instability (MRI) leads to a rapid growth for these weak seed fields. Although plenty of MRI studies exist for accretion disks, the application of their results to core collapse supernovae is inhibited as the physics of supernova cores is substantially different from that of accretion discs.
Aims: We address the problem of growth and saturation of the MRI in core collapse supernovae by studying its evolution by means of semi-global simulations, which combine elements of global and local simulations by taking the presence of global background gradients into account and using a local computational grid. We investigate, in particular, the termination of the growth of the MRI and the properties of the turbulence in the saturated state.
Methods: We analyze the dispersion relation of the MRI to identify different regimes of the instability. This analysis is complemented by semi-global ideal MHD simulations, where we consider core matter in a local computational box (size ∼ 1 km) rotating at sub-Keplerian velocity and where we allow for the presence of a radial entropy gradient, but neglect neutrino radiation.
Results: We identify six regimes of the MRI depending on the ratio of the entropy and angular velocity gradient. Our numerical models confirm the instability criteria and growth rates for all regimes relevant to core-collapse supernovae. The MRI grows exponentially on time scales of milliseconds, the flow and magnetic field geometries being dominated by channel flows. We find MHD turbulence and efficient transport of angular momentum. The MRI growth ceases once the channels are disrupted by resistive instabilities (stemming from to the finite conductivity of the numerical code), and MHD turbulence sets in. From an analysis of the growth rates of the resistive instabilities, we deduce scaling laws for the termination amplitude of the MRI, which agree well with our numerical models. We determine the dependence of the development of large-scale coherent flow structures in the saturated state on the aspect ratio of the simulation boxes.
Conclusions: The MRI can grow rapidly under the conditions considered here, i.e., a rapidly rotating core in hydrostatic equilibrium, possibly endowed with a nonvanishing entropy gradient, leading to fields exceeding 1015~G. More investigations are required to cover the parameter space more comprehensively and to include more physical effects. Title: Relativistic Simulations of Magneto-rotational Core Collapse Authors: Font, J. A.; Cerdá-Durán, P.; Müller, E.; Antón, L. Bibcode: 2009ASPC..406...86F Altcode: We introduce and discuss the basic features of a new numerical code designed to handle ideal MHD flows in dynamical spacetimes in general relativity, and particularly designed to investigate the gravitational collapse of the core of massive stars leading to neutron stars or black holes. After introducing the mathematical framework for the general relativistic MHD equations and the Einstein equations (within the so-called conformal flat condition) we present results from two representative simulations of magneto-rotational stellar core collapse. Our simulations highlight the importance of genuine magnetic effects such as the magneto-rotational instability on the dynamics of the process. Title: Early results from the SAGE-SMC Spitzer legacy Authors: Gordon, Karl D.; Meixner, M.; Blum, R. D.; Reach, W.; Whitney, B. A.; Harris, J.; Indebetouw, R.; Bolatto, A. D.; Bernard, J. -P.; Sewilo, M.; Babler, B. L.; Block, M.; Bot, C.; Bracker, S.; Carlson, L.; Churchwell, E.; Clayton, G. C.; Cohen, M.; Engelbracht, C. W.; Fukui, Y.; Gorjian, V.; Hony, S.; Hora, J. L.; Israel, F.; Kawamura, A.; Leroy, A. K.; Li, A.; Madden, S.; Marble, A. R.; Markwick-Kemper, F.; Meade, M.; Misselt, K. A.; Mizuno, A.; Mizuno, N.; Muller, E.; Oliveira, J. M.; Olsen, K.; Onishi, T.; Paladini, R.; Paradis, D.; Points, S.; Robitaille, T.; Rubin, D.; Sandstrom, K. M.; Sato, S.; Shibai, H.; Simon, J. D.; Smith, L. J.; Srinivasan, S.; Tielens, A. G. G. M.; Vijh, U. P.; van Dyk, S.; van Loon, J. Th.; Volk, K.; Zaritsky, D. Bibcode: 2009IAUS..256..184G Altcode: Early results from the SAGE-SMC (Surveying the Agents of Galaxy Evolution in the tidally-disrupted, low-metallicity Small Magellanic Cloud) Spitzer legacy program are presented. These early results concentrate on the SAGE-SMC MIPS observations of the SMC Tail region. This region is the high H i column density portion of the Magellanic Bridge adjacent to the SMC Wing. We detect infrared dust emission and measure the gas-to-dust ratio in the SMC Tail and find it similar to that of the SMC Body. In addition, we find two embedded cluster regions that are resolved into multiple sources at all MIPS wavelengths. Title: Equation-of-state dependent features in shock-oscillation modulated neutrino and gravitational-wave signals from supernovae Authors: Marek, A.; Janka, H. -T.; Müller, E. Bibcode: 2009A&A...496..475M Altcode: 2008arXiv0808.4136M We present two-dimensional (axisymmetric) neutrino-hydrodynamic simulations of the long-time accretion phase of a 15 M_⊙ progenitor star after core bounce and before the launch of a supernova explosion, when non-radial hydrodynamic instabilities like convection occur in different regions of the collapsing stellar core and the standing accretion shock instability (SASI) leads to large-amplitude oscillations of the stalled shock with a period of tens of milliseconds. Our simulations were performed with the Prometheus-Vertex code, which includes a multi-flavor, energy-dependent neutrino transport scheme and employs an effective relativistic gravitational potential. Testing the influence of a stiff and a soft equation of state for hot neutron star matter, we find that the non-radial mass motions in the supernova core impose a time variability on the neutrino and gravitational-wave signals with larger amplitudes, as well as higher frequencies in the case of a more compact nascent neutron star. After the prompt shock-breakout burst of electron neutrinos, a more compact accreting remnant produces higher neutrino luminosities and higher mean neutrino energies. The observable neutrino emission in the SASI sloshing direction exhibits a modulation of several ten percent in the luminosities and around 1 MeV in the mean energies with most power at typical SASI frequencies between roughly 20 and 100 Hz. The modulation is caused by quasi-periodic variations in the mass accretion rate of the neutron star in each hemisphere. At times later than ~50-100 ms after bounce, the gravitational-wave amplitude is dominated by the growing low-frequency (⪉200 Hz) signal associated with anisotropic neutrino emission. A high-frequency wave signal results from nonradial gas flows in the outer layers of the anisotropically accreting neutron star. Right after bounce such nonradial mass motions occur due to prompt post-shock convection in both considered cases and contribute mostly to the early wave production around 100 Hz. Later they are instigated by the SASI and by convective overturn that vigorously stir the neutrino-heating and cooling layers, and also by convective activity developing below the neutrinosphere. The gravitational-wave power then peaks at about 300-800 Hz, connected to changes in the mass quadrupole moment on a timescale of milliseconds. Distinctively higher spectral frequencies originate from the more compact and more rapidly contracting neutron star. Both the neutrino and gravitational-wave emission therefore carry information that is characteristic of the properties of the nuclear equation of state in the hot remnant. The detectability of the SASI effects in the neutrino and gravitational-wave signals is briefly discussed. Title: Cool Gas in the Magellanic Stream Authors: Matthews, D.; Staveley-Smith, L.; Dyson, P.; Muller, E. Bibcode: 2009ApJ...691L.115M Altcode: 2009arXiv0901.3415M We present the first direct detection of cold atomic gas in the Magellanic Stream, through 21 cm line absorption toward a background radio source, J0119-6809, using the Australia Telescope Compact Array. Two absorption components were identified at heliocentric velocities 218.6 km s-1 and 227.0 km s-1, with optical depths of τ ≈ 0.02. The corresponding H I emission region has a column density in excess of 2 × 1020 cm-2. The inferred spin temperature of the emitting gas is ~70 K. We failed to find cool gas in observations of three other radio continuum sources. Although we have definitively detected cool gas in the Stream, its spin temperature is higher than similar components in the LMC, SMC, and Bridge, and its contribution to the total H I density is probably lower. No corresponding 12CO(J = 1→ 0) or dust appears to be associated with the cool gas, suggesting that the cloud is not forming stars. Title: Cluster magnetic fields from galactic outflows Authors: Donnert, J.; Dolag, K.; Lesch, H.; Müller, E. Bibcode: 2009MNRAS.392.1008D Altcode: 2008arXiv0808.0919D We performed cosmological, magnetohydrodynamical simulations to follow the evolution of magnetic fields in galaxy clusters, exploring the possibility that the origin of the magnetic seed fields is galactic outflows during the starburst phase of galactic evolution. To do this, we coupled a semi-analytical model for magnetized galactic winds as suggested by Bertone, Vogt & Enßlin to our cosmological simulation. We find that the strength and structure of magnetic fields observed in galaxy clusters are well reproduced for a wide range of model parameters for the magnetized, galactic winds and do only weakly depend on the exact magnetic structure within the assumed galactic outflows. Although the evolution of a primordial magnetic seed field shows no significant differences to that of galaxy cluster fields from previous studies, we find that the magnetic field pollution in the diffuse medium within filaments is below the level predicted by scenarios with pure primordial magnetic seed field. We therefore conclude that magnetized galactic outflows and their subsequent evolution within the intracluster medium can fully account for the observed magnetic fields in galaxy clusters. Our findings also suggest that measuring cosmological magnetic fields in low-density environments such as filaments is much more useful than observing cluster magnetic fields to infer their possible origin. Title: The Dust-to-Gas Ratio in the Small Magellanic Cloud Tail Authors: Gordon, K. D.; Bot, C.; Muller, E.; Misselt, K. A.; Bolatto, A.; Bernard, J. -P.; Reach, W.; Engelbracht, C. W.; Babler, B.; Bracker, S.; Block, M.; Clayton, G. C.; Hora, J.; Indebetouw, R.; Israel, F. P.; Li, A.; Madden, S.; Meade, M.; Meixner, M.; Sewilo, M.; Shiao, B.; Smith, L. J.; van Loon, J. Th.; Whitney, B. A. Bibcode: 2009ApJ...690L..76G Altcode: 2008arXiv0811.2789G The Tail region of the Small Magellanic Cloud (SMC) was imaged using the MIPS instrument on the Spitzer Space Telescope as part of the SAGE-SMC Spitzer Legacy. Diffuse infrared emission from dust was detected in all the MIPS bands. The Tail gas-to-dust ratio was measured to be 1200 ± 350 using the MIPS observations combined with existing IRAS and H I observations. This gas-to-dust ratio is higher than the expected 500-800 from the known Tail metallicity indicating possible destruction of dust grains. Two cluster regions in the Tail were resolved into multiple sources in the MIPS observations and local gas-to-dust ratios were measured to be ~ 440 and ~ 250 suggest dust formation and/or significant amounts of ionized gas in these regions. These results support the interpretation that the SMC Tail is a tidal Tail recently stripped from the SMC that includes gas, dust, and young stars. Title: A new general relativistic magnetohydrodynamics code for dynamical spacetimes Authors: Cerdá-Durán, P.; Font, J. A.; Antón, L.; Müller, E. Bibcode: 2008A&A...492..937C Altcode: 2008arXiv0804.4572C We present a new numerical code that solves the general relativistic magneto-hydrodynamical (GRMHD) equations coupled to the Einstein equations for the evolution of a dynamical spacetime within a conformally-flat approximation. This code has been developed with the main objective of studying astrophysical scenarios in which both, high magnetic fields and strong gravitational fields appear, such as the magneto-rotational collapse of stellar cores, the collapsar model of GRBs, and the evolution of neutron stars. The code is based on an existing and thoroughly tested purely hydrodynamical code and on its extension to accommodate weakly magnetized fluids (passive magnetic-field approximation). These codes have been applied in the past to simulate the aforementioned scenarios with increasing levels of sophistication in the input physics. The numerical code we present here is based on high-resolution shock-capturing schemes to solve the GRMHD equations, which are cast in first-order, flux-conservative hyperbolic form, together with the flux constraint transport method to ensure the solenoidal condition of the magnetic field. Since the astrophysical applications envisaged do not deviate significantly from spherical symmetry, the conformal flatness condition approximation is used for the formulation of the Einstein equations; this has repeatedly shown to yield very good agreement with full general relativistic simulations of core-collapse supernovae and the evolution of isolated neutron stars. In addition, the code can handle several equations of state, from simple analytical expressions to microphysical tabulated ones. In this paper we present stringent tests of our new GRMHD numerical code, which show its ability to handle all aspects appearing in the astrophysical scenarios for which the code is intended, namely relativistic shocks, highly magnetized fluids, and equilibrium configurations of magnetized neutron stars. As an application, magneto-rotational core-collapse simulations of a realistic progenitor are presented and the results compared with our previous findings in the passive magnetic-field approximation. Title: The core helium flash revisited. I. One and two-dimensional hydrodynamic simulations Authors: Mocák, M.; Müller, E.; Weiss, A.; Kifonidis, K. Bibcode: 2008A&A...490..265M Altcode: 2008arXiv0805.1355M Context: We investigate the hydrodynamics of the core helium flash close to its peak. Past research concerned with the dynamics of this event is inconclusive. However, the most recent multidimensional hydrodynamic studies suggest a quiescent behavior and seem to rule out an explosive scenario.
Aims: Depending on initial conditions, turbulence models, grid resolution, and dimensionality of the simulation, previous work indicated that the core helium flash could lead either to the disruption of a low-mass star or to a quiescent quasi-hydrostatic evolution. We attempt to clarify this issue by simulating the evolution with advanced numerical methods and detailed microphysics.
Methods: Assuming spherical or axial symmetry, we simulate the evolution of the helium core of a 1.25~M star with a metallicity Z=0.02 during the core helium flash at its peak with a grid-based hydrodynamical code.
Results: We find that the core helium flash neither rips the star apart, nor significantly alters its structure, since convection plays a crucial role in keeping the star in hydrostatic equilibrium. In addition, our simulations indicate the presence of overshooting, which implies new predictions concerning mixing of chemical species in red giants. Title: Exploring the relativistic regime with Newtonian hydrodynamics. II. An effective gravitational potential for rapid rotation Authors: Müller, B.; Dimmelmeier, H.; Müller, E. Bibcode: 2008A&A...489..301M Altcode: 2008arXiv0802.2459M We present the generalization of a recently introduced

modified gravitational potential for self-gravitating fluids. The

use of this potential allows for an accurate approximation of

general relativistic effects in an otherwise Newtonian hydrodynamics

code also in cases of rapid rotation. We test this approach in

numerical simulations of astrophysical scenarios related to compact

stars, like supernova core collapse with both a simplified and

detailed microphysical description of matter, and rotating neutron

stars in equilibrium. We assess the quality of the new potential,

and demonstrate that it provides a significant improvement compared

to previous formulations for such potentials. Newtonian simulations

of compact objects employing such an effective relativistic

potential predict inaccurate pulsation frequencies despite the

excellent agreement of the collapse dynamics and structure of the

compact objects with general relativistic results. We analyze and

discuss the reason for this behavior. Title: The ALFA Zone of Avoidance Survey Authors: Henning, P. A.; Springob, C. M.; Day, F.; Minchin, R.; Momjian, E.; Catinella, B.; Muller, E.; Koribalski, B.; Masters, K.; Pantoja, C.; Putman, M.; Rosenberg, J. L.; Schneider, S.; Staveley-Smith, L. Bibcode: 2008AIPC.1035..246H Altcode: The Arecibo L-Band Feed Array (ALFA) Zone of Avoidance (ZOA) team is mapping the distribution of low-Galactic-latitude galaxies and large-scale structures through detection of galaxies'21-cm emission with ALFA. This ZOA survey finds new HI galaxies which lie hidden behind the Milky Way, and also provides redshifts for partially-obscured galaxies known at other wavelengths. Two precursor regions which straddle the Galactic plane have been observed to date, totalling 140 square degrees, with 72 HI galaxies detected. Detections through the inner Galaxy generally have no cataloged counterparts in any other waveband, due to the heavy extinction and stellar confusion. Detections through the outer Galaxy are more likely to have 2MASS counterparts, and we provide redshifts for these galaxies. A third region, through the Taurus molecular cloud, has also been observed. The full ALFA ZOA survey will reveal more previously unknown galaxies and map low-latitude large-scale structures. Title: The ALFA Zone of Avoidance Survey: Results from the Precursor Observations Authors: Springob, C. M.; Henning, P. A.; Catinella, B.; Day, F.; Minchin, R.; Momjian, E.; Koribalski, B.; Masters, K. L.; Muller, E.; Pantoja, C.; Putman, M.; Rosenberg, J. L.; Schneider, S.; Staveley-Smith, L. Bibcode: 2008IAUS..244..383S Altcode: 2007IAUS..244..383S; 2007arXiv0708.1724S The Arecibo L-band Feed Array Zone of Avoidance Survey (ALFA ZOA) will map 1350-1800 deg2 at low Galactic latitude, providing HI spectra for galaxies in regions of the sky where our knowledge of local large scale structure remains incomplete, owing to obscuration from dust and high stellar confusion near the Galactic plane. Because of these effects, a substantial fraction of the galaxies detected in the survey will have no optical or infrared counterparts. However, near infrared follow up observations of ALFA ZOA sources found in regions of lowest obscuration could reveal whether some of these sources could be objects in which little or no star formation has taken place (“dark galaxies”). We present here the results of ALFA ZOA precursor observations on two patches of sky totaling 140 deg2 (near l = 40°, and l = 192°). We have measured HI parameters for detections from these observations, and cross-correlated with the NASA/IPAC Extragalactic Database (NED). A significant fraction of the objects have never been detected at any wavelength. For those galaxies that have been previously detected, a significant fraction have no previously known redshift, and no previous HI detection. Title: The Arecibo Galaxy Environment Survey Potential for finding Dark Galaxies and Results so far Authors: Minchin, R. F.; Auld, R.; Cortese, L.; Davies, J. I.; Momjian, E.; Taylor, R.; Catinella, B.; Henning, P.; Linder, S.; Muller, E.; O'Neil, K.; Rosenberg, J.; Sabatini, S.; Schneider, S. E.; Stage, M.; van Driel, W.; van Driel Bibcode: 2008IAUS..244..112M Altcode: 2007IAUS..244..112M The Arecibo Galaxy Environment Survey is a blind neutral hydrogen survey using the ALFA multibeam receiver at Arecibo Observatory to reach unprecedented sensitivities in a number of selected fields in the local Universe. When completed the survey will cover 200 square degrees out to a distance of at least 270 Mpc. If a population of gas-rich dark galaxies exists, then this survey is in a prime position to uncover that population.

So far 20 square degrees have been covered in the regions of Abell 1367, the Virgo Cluster, the NGC 7332/9 galaxy pair and the isolated galaxy NGC 1156. Over 200 sources have been found, including a number that have no obvious optical counterparts. We discuss here the potential of AGES for uncovering more such objects and the characteristics of the dark sources identified to date. Title: Large Scale Structure and Turbulence: The Mopra G333 Survey Authors: Cunningham, M.; Lo, N.; Kramer, C.; Bains, I.; Jones, P.; Burton, M.; Muller, E.; Ossenkopf, V. Bibcode: 2008EAS....31....9C Altcode: We have used the new broadband capabilities of the Mopra telescope to map the distribution of 26 different molecular transitions in an approximately 1 degree square region of the southern Galactic plane (the G333/RCW106 giant molecular cloud complex). The aim is to addresss observationally some of the key questions about the dynamical processes surrounding massive star formation (e.g. massive stellar winds and large-scale galactic flows) and their relative importance in regulating the star formation process. These dynamical processes help drive the turbulent motions, which are ubiquitous in giant molecular clouds (GMCs). The multi-molecular line nature of this survey is what distinguishes it from similar surveys and is crucial for gaining a clear picture of the energetics and dynamics of the gas. Investigating and understanding the chemistry of this region is a necessary part of the project if the molecular line observations are to be interpreted physically. Title: Atomic Gas Associated with GMCs in the LMC Authors: Hughes, Annie; Wong, T.; Ott, J.; Muller, E.; Pineda, J. L.; Mizuno, Y. Bibcode: 2008ASSP....5..293H Altcode: 2008glv..book..293H No abstract at ADS Title: An Observational Study of the GMCs in the Magellanic Clouds in Millimeter and Submillimeter Wavelengths Authors: Minamidani, T.; Mizuno, N.; Mizuno, Y.; Kawamura, A.; Onishi, T.; Hasegawa, T.; Tatematsu, K.; Ikeda, M.; Moriguchi, Y.; Yamaguchi, N.; Ott, J.; Wong, T.; Muller, E.; Pineda, J. L.; Hughes, A.; Staveley-Smith, L.; Klein, U.; Mizuno, A.; Nikolić, S.; Booth, R. S.; Heikkilä, A.; Nyman, L. -Å.; Lerner, M.; Garay, G.; Kim, S.; Rubio, M.; Fukui, Y. Bibcode: 2008ASSP....5..311M Altcode: 2008glv..book..311M No abstract at ADS Title: Multidimensional hydrodynamic simulations of the core helium flash . Authors: Mocak, M.; Müller, E.; Weiss, A.; Kifonidis, K. Bibcode: 2008MmSAI..79..729M Altcode: Using an initial model, which is obtained from the evolution of a 1.25 M star with a metallicity of 0.02 computed with the Garching stellar evolution code, we investigate the hydrodynamics of the core helium flash near its peak. Past research concerned with the dynamics of the core helium flash is inconclusive. Its results range from a confirmation of the standard picture, where the star remains in hydrostatic equilibrium during the flash \citet{deu96}, up to a disruption of the star \citet{edw69}. However, the most recent multidimensional hydrodynamic study \citet{dea06} suggests a quiescent behavior during the flash and seems to rule out an explosive scenario. Here we present the first results of a new comprehensive study of the core helium flash, which seem to confirm this qualitative behavior. Title: Hα Emission from the Magellanic Bridge Authors: Muller, E.; Parker, Q. A. Bibcode: 2007PASA...24...69M Altcode: 2007arXiv0706.4037M We present here a preliminary report and commentary of recently processed observations of Hα emission towards the Magellanic Bridge. These data have been analysed in an attempt to quantify the extent to which the stellar population is capable of reshaping the local ISM. We find that the Hα emission regions are small, weak and sparsely distributed, consistent with a relatively quiescent and inactive ISM where radiative and collisional ionisation is inefficient and sporadic. This suggests that energetic processes at the small scale (i.e. ~tens of pc) do not dominate the energy balance within the ISM of the Bridge, which therefore hosts a pristine turbulent structure, otherwise inaccessible within our own Galaxy. We find Hα emission that is well correlated with detected 12CO(1-0) line emission (a proxy for molecular hydrogen), as well as other easily identified ring-like Hi features. Title: Generic Gravitational-Wave Signals from the Collapse of Rotating Stellar Cores Authors: Dimmelmeier, H.; Ott, C. D.; Janka, H. -T.; Marek, A.; Müller, E. Bibcode: 2007PhRvL..98y1101D Altcode: 2007astro.ph..2305D We perform general relativistic (GR) simulations of stellar core collapse to a protoneutron star, using a microphysical equation of state (EOS) and an approximation of deleptonization. We show that for a wide range of rotation rates and profiles the gravitational-wave (GW) burst signals from the core bounce are generic, known as type I. In our systematic study, using both GR and Newtonian gravity, we identify and quantify the influence of rotation, the EOS, and deleptonization on this result. Such a generic type of signal templates will facilitate a more efficient search in current and future GW detectors of both interferometric and resonant type. Title: The Arecibo Galaxy Environments Survey - Description of the Survey and Early Results Authors: Minchin, R. F.; Auld, R.; Davies, J. I.; Catinella, B.; Cortese, L.; Linder, S.; Momjian, E.; Muller, E.; O'Neil, K.; Rosenberg, J.; Sabatini, S.; Schneider, S. E.; Stage, M.; van Driel, W.; AGES Team Bibcode: 2007IAUS..235..227M Altcode: 2006astro.ph.10629M; 2006IAUS..235E.284M The Arecibo Galaxy Envrionments Survey (AGES) is a 2000-hour neutral hydrogen survey using the new Arecibo L-band Feed Array multibeam instrument at Arecibo Observatory. It covers 200 square degrees of sky, sampling a range of environments from the Local Void through to the Virgo Cluster with higher sensitivity, spatial resolution and velocity resolution than previous neutral hydrogen surveys. AGES will address a number of scientific objectives, including: 1. The HI mass function in different environments. 2. Baryonic mass density. 3. HVCs, dwarf galaxies etc. 4. Tidal features. 5. Dynamical masses. 6. Low column density HI. 7. Isolated HI clouds - dark galaxies. 8. HI and QSO absorption features. 9. Spatial distribution of HI selected galaxies The first field to be covered, 5 square degrees centred on the optically-isolated galaxy NGC 1156, has revealed at least two new companions to NGC 1156, one of which may be interacting with the galaxy. This field also contains 51 definite detections in the volume beyond NGC 1156, including one with no optical counterpart. A further 30 candidates have been identified for follow-up observations. Title: Convective processes and hydromagnetic instabilities in core collapse supernova simulations Authors: Obergaulinger, M.; Hammer, N. J.; Müller, E. Bibcode: 2007IAUS..239..323O Altcode: No abstract at ADS Title: Internal shocks in relativistic outflows: collisions of magnetized shells Authors: Mimica, P.; Aloy, M. A.; Müller, E. Bibcode: 2007A&A...466...93M Altcode: 2006astro.ph.11765M Aims: We study the collision of magnetized irregularities (shells) in relativistic outflows in order to explain the origin of the generic phenomenology observed in the non-thermal emission of both blazars and gamma-ray bursts. We focus on the influence of the magnetic field on the collision dynamics, and we investigate how the properties of the observed radiation depend on the strength of the initial magnetic field and on the initial internal energy density of the flow.
Methods: The collisions of magnetized shells and the radiation resulting from these collisions are calculated using the 1D relativistic magnetohydrodynamics code MRGENESIS. The interaction of the shells with the external medium prior to their collision is also determined using an exact solver for the corresponding 1D relativistic magnetohydrodynamic Riemann problem. In both cases we assume that the magnetic field is oriented perpendicular to the flow direction.
Results: Our simulations show that two magnetization parameters - the ratio of magnetic energy density and thermal energy density, αB, and the ratio of magnetic energy density and mass-energy density, σ - play an important role in the pre-collision phase, while the dynamics of the collision and the properties of the light curves depend mostly on the magnetization parameter σ. Comparing synthetic light curves computed from hydrodynamic and magnetohydrodynamic models we find that the assumption commonly made in the former models that the magnetization parameter αB is constant and uniform, holds rather well, if αB < 0.01. The interaction of the shells with the external medium changes the flow properties at their edges prior to the collision. For sufficiently dense shells moving at large Lorentz factors (≳25) these properties depend only on the magnetization parameter σ. Internal shocks in GRBs may reach maximum efficiencies of conversion of kinetic into thermal energy between 6% and 10%, while in case of blazars, the maximum efficiencies are ~2%. Title: Analysis of the Neutrino Antineutrino Annihilation near Accreting Stellar Black Holes Authors: Birkl, R.; Aloy, M. A.; Janka, H. -Th.; Müller, E. Bibcode: 2007sgrb.conf...11B Altcode: We investigate the deposition of energy and momentum due to the annihilation of neutrinos (ν) and antineutrinos (barν) in the vicinity of steady, axisymmetric accretion tori around stellar-mass black holes (BHs). This process is widely considered as an energy source for driving ultrarelativistic outflows with the potential to produce gamma-ray bursts. We analyze the influence of general relativistic (GR) effects in combination with different neutrinosphere properties on the νbarν-annihilation efficiency and spatial distribution of the energy deposition rate. Assuming axial symmetry, we numerically compute the annihilation rate 4-vector. For this purpose, we construct the local neutrino distribution by ray-tracing neutrino trajectories in a Kerr space-time using null geodesics. We vary the value of the dimensionless specific angular momentum a of the central BH, which provides the gravitational field in our models. We also study different shapes of the neutrinospheres, spheres, thin disks, and thick accretion tori, whose structure ranges from idealized tori to equilibrium non-selfgravitating matter distributions. Furthermore, we compute Newtonian models where the influence of the gravitational field on the annihilation process is neglected. Results: Compared to Newtonian calculations, GR effects increase the total annihilation rate measured by an observer at infinity by a factor of two when the neutrinosphere is a thin disk, but the increase is only ≈25% for toroidal and spherical neutrinospheres. Comparing cases with similar luminosities, thin disk models yield the highest energy deposition rates by νbarν-annihilation, and spherical neutrinospheres the lowest ones, independently of whether GR effects are included. Increasing a from 0 to 1 enhances the energy deposition rate measured by an observer at infinity by roughly a factor of 2 due to the change of the inner radius of the neutrinosphere. General relativity and rotation cause important differences in the spatial distri bution of the energy deposition rate by νbarν-annihilation. Title: Commission 35: Stellar Constitution Authors: Dziembowski, Wojciech A.; D'Antona, Francesca; Charbonnel, C.; Christensen-Dalsgaard, J.; Guzik, J.; Langer, N.; Larson, R.; Liebert, J.; Meynet, G.; Müller, E.; Saio, H.; Vandenberg, D. Bibcode: 2007IAUTA..26..205D Altcode: Ihe triennial report from Commission 35 covers its organizational activities and highlights accomplishments in various topics of stellar interior physics. Title: Neutrino pair annihilation near accreting, stellar-mass black holes Authors: Birkl, R.; Aloy, M. A.; Janka, H. -Th.; Müller, E. Bibcode: 2007A&A...463...51B Altcode: 2006astro.ph..8543B Context: We investigate the deposition of energy and momentum due to the annihilation of neutrinos (ν) and antineutrinos (barν) in the vicinity of steady, axisymmetric accretion tori around stellar-mass black holes (BHs). This process is widely considered as an energy source for driving ultrarelativistic outflows with the potential to produce gamma-ray bursts.
Aims: We analyze the influence of general relativistic (GR) effects in combination with different neutrinosphere properties on the νbarν-annihilation efficiency and spatial distribution of the energy deposition rate.
Methods: Assuming axial symmetry, we numerically compute the annihilation rate 4-vector. For this purpose, we construct the local neutrino distribution by ray-tracing neutrino trajectories in a Kerr space-time using null geodesics. We vary the value of the dimensionless specific angular momentum a of the central BH, which provides the gravitational field in our models. We also study different shapes of the neutrinospheres, spheres, thin disks, and thick accretion tori, whose structure ranges from idealized tori to equilibrium non-selfgravitating matter distributions. Furthermore, we compute Newtonian models where the influence of the gravitational field on the annihilation process is neglected.
Results: Compared to Newtonian calculations, GR effects increase the total annihilation rate measured by an observer at infinity by a factor of two when the neutrinosphere is a thin disk, but the increase is only ≈25% for toroidal and spherical neutrinospheres. Comparing cases with similar luminosities, thin disk models yield the highest energy deposition rates by νbarν-annihilation, and spherical neutrinospheres the lowest ones, independently of whether GR effects are included. Increasing a from 0 to 1 enhances the energy deposition rate measured by an observer at infinity by roughly a factor of 2 due to the change of the inner radius of the neutrinosphere. General relativity and rotation cause important differences in the spatial distribution of the energy deposition rate by νbarν-annihilation. Title: Turbulence in the G333 molecular cloud Authors: Jones, P. A.; Cunningham, M. R.; Bains, I.; Muller, E.; Wong, T.; Burton, M. G. Bibcode: 2007IAUS..237..429J Altcode: 2006IAUS..237E.138J We present some first results of the analysis of turbulence in the G333 molecular cloud complex. Observations were obtained for 3-mm transitions of ^ 13CO, C^18O, CS and C^34S with the Mopra telescope, with a resolution around 35 arcsec. Up to 16 other transitions will be mapped simultaneously in the 2006 season. An area 1 x 1.5 degree was mapped in ^13CO, and the other weaker tracers mapped in the dense regions to obtain complementary information from tracers of different critical density. Here we present some results from power spectra and velocity-component analysis. Title: The Arecibo galaxy environment survey - a sensitive survey for neutral hydrogen in the local Universe Authors: Minchin, R.; Auld, R.; Cortese, L.; Davies, J.; Momjian, E.; Taylor, R.; Catinella, B.; Henning, P.; Linder, S.; Muller, E.; O'Neil, K.; Rosenberg, J.; Sabatini, S.; Schneider, S.; Stage, M.; van Driel, W. Bibcode: 2007mru..confE..27M Altcode: 2007PoS....52E..27M No abstract at ADS Title: The ALFA Zone of Avoidance Survey: Results from the Precursor Observations Authors: Springob, Chris M.; Henning, P. A.; Catinella, B.; Day, F.; Minchin, R.; Momjian, E.; Koribalski, B.; Masters, K. L.; Muller, E.; Pantoja, C.; Putman, M.; Rosenberg, J. L.; Schneider, S.; Staveley-Smith, L. Bibcode: 2006AAS...209.9504S Altcode: 2006BAAS...38Q1034S We present new extragalactic 21 cm observations in the Galactic Plane region. These observations are a precursor to a large scale, extragalactic, zone of avoidance survey with the Arecibo L-band Feed Array (ALFA). The data for this survey are being taken concurrently with a Galactic survey and a pulsar survey. Full survey observations, which will begin in 2007, will reveal local large scale structure in a part of the extragalactic sky that is relatively unexplored due to the obscuration of optical light by dust in our Galaxy. One of these surveys will have an integration time of 268 seconds per point in the inner Galaxy and 134 seconds in the outer Galaxy, covering |b|<5 degrees, while the other will have an integration time of only 5 seconds per point, covering |b|<10 degrees with an rms of roughly 6 mJy. No other extragalactic ALFA survey will cover these latitudes. Precursor observations have been taken using the latter observational setup on two patches of sky totaling 140 square degrees (one near l=40 degrees, and the other near l=192 degrees). We have measured HI parameters for detections from these observations, and cross-correlated with the NASA/IPAC Extragalactic Database. A significant fraction of the objects are new, having never been detected at any wavelength. For those galaxies that have been previously detected, the majority have no previously known redshift, and and no previous HI detection. This research was performed while C.M.S. held a National Research Council Research Associateship Award at the Naval Research Laboratory. Basic research in astronomy at the Naval Research Laboratory is funded by the Office of Naval Research. P.A.H. acknowledges support from NSF grant AST-0506676. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation. Title: Earthwalk Authors: Muller, E. Bibcode: 2006AGUFMED11A1183M Altcode: When the weather is nice, I like to take my students on a walk to the center of the earth. Earthwalk is a hands-on and feet-on activity that gets students outdoors, having fun, moving and learning about the structures of the earth. Earthwalk is a lesson to help students visualize our planets size and scale. This activity has students calculate the ratio of a scaled 100m cross-sectional earth, mark the boundaries between major planetary layers, walk from the center of the earth to the surface and draw proportional manmade and natural surface features (mountains, building, mine shafts, etc). This lesson effectively integrates content and pedagogy while touching on skills and topics such as math, measurement, science, writing skills (they have to take notes), reading, listening and group dynamics. This activity fits well into the earth science curriculum by introducing basic seismology; tectonic, geochemistry and heat transfer concepts. Besides showcasing this lesson, a limited number of Earth Anatomy posters will be distributed. Title: The Arecibo Galaxy Environment Survey: precursor observations of the NGC 628 group Authors: Auld, R.; Minchin, R. F.; Davies, J. I.; Catinella, B.; van Driel, W.; Henning, P. A.; Linder, S.; Momjian, E.; Muller, E.; O'Neil, K.; Sabatini, S.; Schneider, S.; Bothun, G.; Cortese, L.; Disney, M.; Hoffman, G. L.; Putman, M.; Rosenberg, J. L.; Baes, M.; de Blok, W. J. G.; Boselli, A.; Brinks, E.; Brosch, N.; Irwin, J.; Karachentsev, I. D.; Kilborn, V. A.; Koribalski, B.; Spekkens, K. Bibcode: 2006MNRAS.371.1617A Altcode: 2006MNRAS.tmp..953A; 2006astro.ph..7452A The Arecibo Galaxy Environment Survey (AGES) is one of several HI surveys utilizing the new Arecibo L-band Feed Array (ALFA) fitted to the 305-m radio telescope at Arecibo.a The survey is specifically designed to investigate various galactic environments to higher sensitivity, higher velocity resolution and higher spatial resolution than previous fully sampled, 21-cm multibeam surveys. The emphasis is on making detailed observations of nearby objects although the large system bandwidth (100MHz) will allow us to quantify the HI properties over a large instantaneous velocity range.

In this paper, we describe the survey and its goals and present the results from the precursor observations of a 5 × 1-deg2 region containing the nearby (~10Mpc) NGC 628 group. We have detected all the group galaxies in the region including the low-mass (MHI ~107Msolar) dwarf, dw0137+1541. The fluxes and velocities for these galaxies compare well with previously published data. There is no intragroup neutral gas detected down to a limiting column density of 2 × 1018cm-2.

In addition to the group galaxies we have detected 22 galaxies beyond the NGC 628 group, nine of which are previously uncatalogued. We present the HI data for these objects and also SuperCOSMOS images for possible optical galaxies that might be associated with the HI signal. We have used V/Vmax analysis to model how many galaxies beyond 1000kms-1 should be detected and compare this with our results. The predicted number of detectable galaxies varies depending on the HI mass function (HIMF) used in the analysis. Unfortunately the precursor survey area is too small to determine whether this is saying anything fundamental about the HIMF or simply highlighting the effect of low number statistics. This is just one of many questions that will be addressed by the complete AGES survey. Title: Axisymmetric simulations of magnetorotational core collapse: approximate inclusion of general relativistic effects Authors: Obergaulinger, M.; Aloy, M. A.; Dimmelmeier, H.; Müller, E. Bibcode: 2006A&A...457..209O Altcode: 2006astro.ph..2187O We continue our investigations of the magnetorotational collapse of stellar cores by discussing simulations performed with a modified Newtonian gravitational potential that mimics general relativistic effects. The approximate TOV gravitational potential used in our simulations captures several basic features of fully relativistic simulations quite well. In particular, it is able to correctly reproduce the behavior of models that show a qualitative change both of the dynamics and the gravitational wave signal when switching from Newtonian to fully relativistic simulations. For models where the dynamics and gravitational wave signals are already captured qualitatively correctly by a Newtonian potential, the results of the Newtonian and the approximate TOV models differ quantitatively. The collapse proceeds to higher densities with the approximate TOV potential, allowing for a more efficient amplification of the magnetic field by differential rotation. The strength of the saturation fields (∼ 1015 ~ G at the surface of the inner core) is a factor of two to three higher than in Newtonian gravity. Due to the more efficient field amplification, the influence of magnetic fields is considerably more pronounced than in the Newtonian case for some of the models. As in the Newtonian case, sufficiently strong magnetic fields slow down the core's rotation and trigger a secular contraction phase to higher densities. More clearly than in Newtonian models, the collapsed cores of these models exhibit two different kinds of shock generation. Due to magnetic braking, a first shock wave created during the initial centrifugal bounce at subnuclear densities does not suffice for ejecting any mass, and the temporarily stabilized core continues to collapse to supranuclear densities. Another stronger shock wave is generated during the second bounce as the core exceeds nuclear matter density. The gravitational wave signal of these models does not fit into the standard classification. Therefore, in the first paper of this series we introduced a new type of gravitational wave signal, which we call type IV or “magnetic type”. This signal type is more frequent for the approximate relativistic potential than for the Newtonian one. Most of our weak-field models are marginally detectable with the current LIGO interferometer for a source located at a distance of 10 kpc. Strongly magnetized models emit a substantial fraction of their GW power at very low frequencies. A flat spectrum between 10 Hz and ⪉ 100 kHz denotes the generation of a jet-like hydromagnetic outflow. Title: Multidimensional supernova simulations with approximative neutrino transport. I. Neutron star kicks and the anisotropy of neutrino-driven explosions in two spatial dimensions Authors: Scheck, L.; Kifonidis, K.; Janka, H. -Th.; Müller, E. Bibcode: 2006A&A...457..963S Altcode: 2006astro.ph..1302S We study hydrodynamic instabilities during the first seconds of core-collapse supernovae by means of 2D simulations with approximative neutrino transport and boundary conditions that parameterize the effects of the contracting neutron star and allow us to obtain sufficiently strong neutrino heating and, hence, neutrino-driven explosions. Confirming more idealised studies, as well as supernova simulations with spectral transport, we find that random seed perturbations can grow by hydrodynamic instabilities to a globally asymmetric mass distribution in the region between the nascent neutron star and the accretion shock, leading to a dominance of dipole (l=1) and quadrupole (l=2) modes in the explosion ejecta, provided the onset of the supernova explosion is sufficiently slower than the growth time scale of the low-mode instability. By gravitational and hydrodynamic forces, the anisotropic mass distribution causes an acceleration of the nascent neutron star, which lasts for several seconds and can propel the neutron star to velocities of more than 1000 km s-1. Because the explosion anisotropies develop chaotically and change by small differences in the fluid flow, the magnitude of the kick varies stochastically. No systematic dependence of the average neutron star velocity on the explosion energy or the properties of the considered progenitors is found. Instead, the anisotropy of the mass ejection, and hence of the kick, seems to increase when the nascent neutron star contracts more quickly, and thus low-mode instabilities can grow more rapidly. Our more than 70 models separate into two groups, one with high and the other with low neutron star velocities and accelerations after one second of post-bounce evolution, depending on whether the l=1 mode is dominant in the ejecta or not. This leads to a bimodality of the distribution when the neutron star velocities are extrapolated to their terminal values. Establishing a link to the measured distribution of pulsar velocities, however, requires a much larger set of calculations and ultimately 3D modelling. Title: Non-spherical core collapse supernovae. II. The late-time evolution of globally anisotropic neutrino-driven explosions and their implications for SN 1987 A Authors: Kifonidis, K.; Plewa, T.; Scheck, L.; Janka, H. -Th.; Müller, E. Bibcode: 2006A&A...453..661K Altcode: 2005astro.ph.11369K Two-dimensional simulations of strongly anisotropic supernova explosions of a nonrotating 15 M blue supergiant progenitor are presented, which follow the hydrodynamic evolution from times shortly after shock formation until hours later. It is shown that explosions which around the time of shock revival are dominated by low-order unstable modes (i.e. by a superposition of the l=2 and l=1 modes, in which the former is strongest), are consistent with all major observational features of SN 1987 A, in contrast to models which show high-order mode perturbations only and were published in earlier work. Among other items, the low-mode models exhibit final iron-group velocities of up to ∼ 3300 km s-1, strong mixing at the He/H composition interface, with hydrogen being mixed downward in velocity space to only 500 km s-1, and a final prolate anisotropy of the inner ejecta with a major to minor axis ratio of about 1.6. The success of low-mode explosions with an energy of about 2×1051 erg to reproduce these observed features is based on two effects: the (by 40%) larger initial maximum velocities of metal-rich clumps compared to our high-mode models, and the initial global deformation of the shock. The first effect protects the (fastest) clumps from interacting with the strong reverse shock that forms below the He/H composition interface, by keeping their propagation timescale through the He-core shorter than the reverse shock formation time. This ensures that the outward motion of the clumps remains always subsonic, and that thus their energy dissipation is minimal (in contrast to the supersonic case). The second effect is responsible for the strong inward mixing of hydrogen: the aspherical shock deposits large amounts of vorticity into the He/H interface layer at early times (around t = 100 s). This triggers the growth of a strong Richtmyer-Meshkov instability that results in a global anisotropy of the inner ejecta at late times (i.e. around t = 10 000 s), although the shock itself has long become spherical by then. The simulations suggest a coherent picture, which explains the observational data of SN 1987 A within the framework of the neutrino-driven explosion mechanism using a minimal set of assumptions. It is therefore argued that other paradigms, which are based on (more) controversial physics, may not be required to explain this event. Title: Surveying The Zone Of Avoidance With The Arecibo L-band Feed Array Authors: Henning, Patricia A.; Springob, C. M.; Catinella, B.; Momjian, E.; Koribalski, B.; Masters, K.; Muller, E.; Pantoja, C.; Putman, M.; Rosenberg, J. L.; Schneider, S.; Staveley-Smith, L. Bibcode: 2006AAS...208.5304H Altcode: 2006BAAS...38..133H We are conducting 21-cm surveys with the Arecibo L-Band Feed Array, searching for HI galaxies at low galactic latitudes, where optical obscuration and infrared confusion preclude the mapping of galaxies and large-scale structures in those wavebands. Galaxies which contain HI are detected by these blind surveys, and their Doppler shifted emission locates them in 3 dimensions.The first survey will be of the inner Galaxy accessible to Arecibo (l=30-75 degrees), within 10 degrees of the Galactic equator, and will be relatively shallow (effective integration time of 8-10 seconds per beam, with rms about 6 mJy). We have completed two small regions using this observing mode (near l=40 degrees, and l=192 degrees). The catalog of HI detections will be presented, and future expectations for the full survey will be discussed.We will also be conducting very deep, pointed observations, with dwell times expected to be more than 260 seconds per pointing, over all longitudes accessible to Arecibo. Our expectations for this very deep low Galactic latitude survey will be presented. Both the shallow and deep surveys are conducted in "commensal" modes with other surveys on the telescope, a Galactic HI survey, and a pulsar survey, respectively.P.A.H. acknowledges support from NSF grant AST-0506676. Title: Detection of Molecular Clouds in the Magellanic Bridge: Candidate Star Formation Sites in a Nearby Low-Metallicity System Authors: Mizuno, N.; Muller, E.; Maeda, H.; Kawamura, A.; Minamidani, T.; Onishi, T.; Mizuno, A.; Fukui, Y. Bibcode: 2006ApJ...643L.107M Altcode: We present the results of a new, wide-field, and broad-ranging survey for 12CO (1-0) emission regions in the nearest and brightest tidal structure: the Magellanic Bridge. We have detected seven sites of 12CO (1-0) emission using the NANTEN telescope in addition to the one detected previously. The integrated CO brightness for these detections ranges between 30 and 140 mK km s-1, corresponding to an estimated molecular mass of (1-7) × 103 Msolar [assuming the CO-to-H2 conversion factor (X-factor) of ~1.4×1021 cm-2 (K km s-1)-1]. The positions of the CO emission regions are generally coincident with sites of bright 100 μm emission, where I100μm>2.6 MJy sr-1, and have narrow line widths of <~2 km s-1, indicating gas in a cold and rather quiescent state. The velocity centroids of the CO spectra are generally consistent with those of the H I spectra, and we suggest that CO clouds are formed after the tidal encounter, rather than being extracted from the SMC. This is supported by the small typical lifetime of CO clouds, which is as short as ~107 yr and much less than the estimated 200 Myr age of the Bridge itself. Title: First Results from the Arecibo Galaxy Environment Survey Authors: Minchin, Robert F.; Auld, R.; Davies, J. I.; Catinella, B.; Linder, S.; Momjian, E.; Muller, E.; Sabatini, S.; Schneider, S. E.; Stage, M. D.; van Driel, W.; AGES Team Bibcode: 2006AAS...208.5306M Altcode: 2006BAAS...38R.134M The Arecibo Galaxy Environment Survey (AGES) is one of several HI surveys using the new Arecibo L-band Feed Array (ALFA) at Arecibo. Over the next few years, it will cover fields in a wide variety of environments, ranging from the Local Void through isolated galaxies, galaxy pairs and galaxy groups to the Virgo Cluster, with higher sensitivity, higher velocity resolution and higher spatial resolution than previous HI surveys. This will enable the environmental dependance of the HI Mass Function (HIMF) to be determined and will also allow low HI-mass, and high HI-mass to light ratio objects to be discovered. Here we present an overview of the survey and initial results from the first survey field, observed in January 2006.The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation Title: Axisymmetric simulations of magneto-rotational core collapse: dynamics and gravitational wave signal Authors: Obergaulinger, M.; Aloy, M. A.; Müller, E. Bibcode: 2006A&A...450.1107O Altcode: 2005astro.ph.10184O Aims.We have performed a comprehensive parameter study of the collapse of rotating, strongly magnetized stellar cores in axisymmetry to determine their gravitational wave signature based on the Einstein quadrupole formula.
Methods: .We use a Newtonian explicit magnetohydrodynamic Eulerian code based on the relaxing-TVD method for the solution of the ideal MHD equations, and apply the constraint-transport method to guarantee a divergence-free evolution of the magnetic field. We neglect effects due to neutrino transport and employ a simplified equation of state. The initial models are polytropes in rotational equilibrium with a prescribed degree of differential rotation and rotational energy. The initial magnetic fields are purely poloidal the field strength ranging from 1010~G to 1013~G. The evolution of the core is followed until a few ten milliseconds past core bounce.
Results: .The initial magnetic fields are amplified mainly by the differential rotation of the core giving rise to a strong toroidal field component with an energy comparable to the rotational energy. The poloidal field component grows by compression during collapse, but does not change significantly after core bounce. In large parts of the simulated cores the growth time of the magneto-rotational instability (MRI) is of the order of a few milliseconds. The saturation field strengths that can be reached both via a pure Ω dynamo or the MRI are of the order of 1015~G at the surface of the core. Sheet-like circulation flows which produce a strong poloidal field component transporting angular momentum outwards develop due to MRI, provided the initial field is not too weak. Weak initial magnetic fields (⪉1011~G) have no significant effect on the dynamics of the core and the gravitational wave signal. Strong initial fields (⪆1012~G) cause considerable angular momentum transport whereby rotational energy is extracted from the collapsed core which loses centrifugal support and enters a phase of secular contraction. The gravitational wave amplitude at bounce changes by up to a few ten percent compared to the corresponding non-magnetic model. If the angular momentum losses are large, the post-bounce model. If the angular momentum losses are large the post-bounce equilibrium state of the core changes from a centrifugally to a pressure supported one. This transition imprints in the gravitational wave signal a reduction of the amplitude of the large-scale oscillations characteristic of cores bouncing due to centrifugal forces. In some models the quasi-periodic large-scale oscillations are replaced by higher frequency irregular oscillations. This pattern defines a new signal type which we call a type IV gravitational wave signal. Collimated bipolar outflows give rise to a unique feature that may allow their detection by means of gravitational wave astronomy: a large positive quadrupole wave amplitude of similar size as that of the bounce signal.
Title: Exploring the relativistic regime with Newtonian hydrodynamics: an improved effective gravitational potential for supernova simulations Authors: Marek, A.; Dimmelmeier, H.; Janka, H. -Th.; Müller, E.; Buras, R. Bibcode: 2006A&A...445..273M Altcode: 2005astro.ph..2161M We investigate the possibility approximating relativistic effects in hydrodynamical simulations of stellar core collapse and post-bounce evolution by using a modified gravitational potential in an otherwise standard Newtonian hydrodynamic code. Different modifications of a previously introduced effective relativistic potential are discussed. Corresponding hydrostatic solutions are compared with solutions of the TOV equations, and hydrodynamic simulations with two different codes are compared with fully relativistic results. One code is applied for one- and two-dimensional calculations with a simple equation of state, and employs either the modified effective relativistic potential in a Newtonian framework or solves the general relativistic field equations under the assumption of the conformal flatness condition (CFC) for the three-metric. The second code allows for full-scale supernova runs including a microphysical equation of state and neutrino transport based on the solution of the Boltzmann equation and its moments equations. We present prescriptions for the effective relativistic potential for self-gravitating fluids to be used in Newtonian codes, which produce excellent agreement with fully relativistic solutions in spherical symmetry, leading to significant improvements compared to previously published approximations. Moreover, they also approximate qualitatively well relativistic solutions for models with rotation. Title: How to blow up a star. Authors: Hillebrandt, W.; Janka, H. -T.; Mueller, E. Bibcode: 2006SciAm.295d..42H Altcode: No abstract at ADS Title: ARPS: an Advanced Radio Isotope Power Subsystem for ExoMars Geophysical Package (GEP) Authors: Mimoun, D.; Biele, J.; Lenoir, B.; Dauscher, A.; Müller, E. Bibcode: 2005AGUFM.P51C0935M Altcode: Within the framework of the ESA Aurora initiative , IPGP, DLR and an international consortium of laboratories launched an initiative aiming at adding on board the ExoMars mission a long life geophysical observatory, called "GEP" (Geophysical package) or "Mars Long Lived Surface Package". The feasibility study of this "geophysical package", carried out with the CNES support, showed the need for studying an alternative source of power to solar panels. Developments related to RTG technologies have been restricted for a long time to the United States and Russian industries. However, the exploration of the remote solar system (in the frame of the ESA Cosmic Vision) as well as long duration planetary missions (such as ExoMars Geophysical Package GEP ) exclude de facto the use of solar panels. A possible solution would be to associate to a radioisotope heat source of Russian origin (of Angel type) a thermo-electrical conversion system of European design. A European consortium of laboratories, including LPM, IPG and DLR (WF and RS) was thus constituted, in order to validate by a study the assumptions on the electric subsystem for the preliminary sizing of the geophysical package. The power of this Advanced radio-isotopic power system (ARPS) should be between 3 and 4 W, and the proposed mass limited to about 3 to 4 kg. This study will be undertaken in collaboration between the LPM, IPGP, DLR-WF and DLR-RS. A preliminary iteration of the GEP power subsystem will be presented, and main trade-off will be considered. Title: Ca II K observations of QSOs in the line-of-sight to the Magellanic Bridge Authors: Smoker, J. V.; Keenan, F. P.; Thompson, H. M. A.; Brüns, C.; Muller, E.; Lehner, N.; Lee, J. -K.; Hunter, I. Bibcode: 2005A&A...443..525S Altcode: 2005astro.ph.10507S We describe medium-resolution spectroscopic observations taken with the ESO Multi-Mode Instrument (emmi) in the Ca ii K line (λ_air=3933.661 Å) towards 7 QSOs located in the line-of-sight to the Magellanic Bridge. At a spectral resolution R = λ/Δλ = 6000, five of the sightlines have a signal-to-noise (S/N) ratio of 20 or higher. Definite Ca absorption due to Bridge material is detected towards 3 objects, with probable detection towards two other sightlines. Gas-phase Ca ii K Bridge and Milky Way abundances or lower limits for the all sightlines are estimated by the use of Parkes 21-cm H i emission line data. These data only have a spatial resolution of 14 arcmin compared with the optical observations which have milli-arcsecond resolution. With this caveat, for the three objects with sound Ca ii K detections, we find that the ionic abundance of Ca ii K relative to H i, A=log(N(Ca K)/N(H i)) for low-velocity Galactic gas ranges from -8.3 to -8.8 dex, with H i column densities varying from 3-6×1020 cm-2. For Magellanic Bridge gas, the values of A are 0.5 dex higher, ranging from -7.8 to -8.2 dex, with N(H i) = 1{-}5×1020 cm-2. Higher values of A correspond to lower values of N(H i), although numbers are small. For the sightline towards B 0251-675, the Bridge gas has two different velocities, and in only one of these is Ca ii tentatively detected, perhaps indicating gas of a different origin or present-day characteristics (such as dust content), although this conclusion is uncertain and there is the possibility that one of the components could be related to the Magellanic Stream. Higher signal-to-noise Ca ii K data and higher resolution H i data are required to determine whether A changes with N(H i) over the Bridge and if the implied difference in the metalicity of the two Bridge components towards B 0251-675 is real. Title: Which physical parameters can be inferred from the emission variability of relativistic jets? Authors: Mimica, P.; Aloy, M. A.; Müller, E.; Brinkmann, W. Bibcode: 2005A&A...441..103M Altcode: 2005astro.ph..6636M We present results of a detailed numerical study and theoretical analysis of the dynamics of internal shocks in relativistic jets and the non-thermal flares associated with these shocks. In our model internal shocks result from collisions of density inhomogeneities (shells) in relativistic jet flows. We find that the merged shell resulting from the inelastic collision of shells has a complicated internal structure due to the non-linear dynamics of the interaction. Furthermore, the instantaneous efficiency for converting kinetic energy into thermal energy is found to be almost twice as high as theoretically expected during the period of significant emission. The Lorentz factors of the internal shocks are correlated with the initial inertial masses of the shells. Because of the complexity of the non-linear evolution the merged shell becomes very inhomogeneous and simple one-zone models are inadequate to extract physical parameters of the emitting region from the resulting light curves. In order to improve on these one-zone approximations, we propose a novel way of analyzing the space-time properties of the emission. Based on these properties we construct an analytic model of non-thermal flares which can be used to constrain some (unobservable) physical parameters of the internal shocks. These are the ratio of the Lorentz factors between the forward and the reverse shock (caused by the shell collision), and the shell crossing times of these shocks. The analytic model is validated by applying it to the synthetic light curves computed from our models. It can equally well be applied to observations. Title: Supernova Asymmetries and Pulsar Kicks --- Views on Controversial Issues Authors: Janka, H. -Th.; Scheck, L.; Kifonidis, K.; Müller, E.; Plewa, T. Bibcode: 2005ASPC..332..363J Altcode: 2004astro.ph..8439J; 2005ASPC..332..372J Two- and three-dimensional simulations demonstrate that hydrodynamic instabilities can lead to low-mode (l=1, 2) asymmetries of the fluid flow in the neutrino-heated layer behind the supernova shock. This provides a natural explanation for aspherical mass ejection and for pulsar recoil velocities even in excess of 1000 km/s. We propose that the bimodality of the pulsar velocity distribution might be a consequence of a dominant l=1 mode in case of the fast component, while higher-mode anisotropy characterizes the postshock flow and SN ejecta during the birth of the slow neutron stars. We argue that the observed large asymmetries of supernovae and the measured high velocities of young pulsars therefore do not imply rapid rotation of the iron core of the progenitor star, nor do they require strong magnetic fields to play a crucial role in the explosion. Anisotropic neutrino emission from accretion contributes to the neutron star acceleration on a minor level, and pulsar kicks do not make a good case for non-standard neutrino physics in the nascent neutron star. Title: CFC+: improved dynamics and gravitational waveforms from relativistic core collapse simulations Authors: Cerdá-Durán, P.; Faye, G.; Dimmelmeier, H.; Font, J. A.; Ibáñez, J. M.; Müller, E.; Schäfer, G. Bibcode: 2005A&A...439.1033C Altcode: 2004astro.ph.12611C Core collapse supernovae are a promising source of detectable gravitational waves. Most of the existing (multidimensional) numerical simulations of core collapse in general relativity were done using approximations of the Einstein field equations. As recently shown by Dimmelmeier et al. (2002a, A&A, 388, 917), Dimmelmeier et al. (2002b, A&A, 393, 523), one of the most interesting such approximations is the so-called conformal flatness condition (CFC) of Isenberg, Wilson; and Mathews. Building on this previous work we present new results from numerical simulations of relativistic rotational core collapse in axisymmetry, with the aim of improving the dynamics and gravitational waveforms. The computer code used for these simulations models the evolution of the coupled system of metric and fluid equations using the 3 + 1 formalism, specialized to a new framework for the gravitational field equations we call CFC+. In this approach we add new degrees of freedom to the original CFC equations, which extend them by terms of second post-Newtonian order. The resulting metric equations are still of elliptic type, but the number of equations is significantly augmented in comparison to the original CFC approach. The hydrodynamic evolution and the CFC spacetime metric are calculated with the code developed by Dimmelmeier et al.(2002a, A&A, 388, 917), which has been conveniently extended to account for the additional CFC+ equations. The corrections included in CFC+ are computed by solving a system of elliptic linear equations. The new formalism is assessed with time evolutions of both rotating neutron stars in equilibrium and gravitational core collapse of rotating polytropes. Gravitational wave signals for a comprehensive sample of collapse models are extracted using either the quadrupole formula or directly from the metric. We discuss our results on the dynamics and the gravitational wave emission through a detailed comparison between CFC and CFC+ simulations. The main conclusion is that, for the neutron star spacetimes analyzed in the present work, no significant differences are found among CFC, CFC+, and full general relativity, which highlights the suitability of the former. Title: Relativistic outflows from remnants of compact object mergers and their viability for short gamma-ray bursts Authors: Aloy, M. A.; Janka, H. -T.; Müller, E. Bibcode: 2005A&A...436..273A Altcode: 2004astro.ph..8291A We present the first general relativistic hydrodynamic models of the launch and evolution of relativistic jets and winds, driven by thermal energy deposition, possibly due to neutrino-antineutrino annihilation, in the close vicinity of black hole-accretion torus systems. The latter are considered to be the remnants of compact object mergers. Our two-dimensional simulations establish the link between models of such mergers and future observations of short gamma-ray bursts by the SWIFT satellite. They show that ultrarelativistic outflow with maximum terminal Lorentz factors around 1000 develops for polar energy deposition rates above some 1048 erg s-1 per steradian, provided the merger environment has a sufficiently low baryon density. By the interaction with the dense accretion torus the ultrarelativistic outflow with Lorentz factors Γ above 100 is collimated into a sharp-edged cone that is embedded laterally by a wind with steeply declining Lorentz factor. The typical semi-opening angles of the Γ > 100 cone are 5°-10°, corresponding to about 0.4-1.5% of the hemisphere and apparent isotropized energies (kinetic plus internal) up to ≈1051 erg although at most 10-30% of the deposited energy is transferred to the outflow with Γ > 100. The viability of post-merger black hole-torus systems as engines of short, hard gamma-ray bursts is therefore confirmed. The annihilation of neutrino-antineutrino pairs radiated from the hot accretion torus appears as a suitable energy source for powerful axial outflow even if only ≈1049 erg are deposited within a cone of 45° half-opening angle around the system axis. Although the torus lifetimes are expected to be only between some 0.01 s and several 0.1 s, our models can explain the durations of all observed short gamma-ray bursts, because different propagation velocities of the front and rear ends will lead to a radial stretching of the ultrarelativistic fireball before transparency is reached. The ultrarelativistic flow reveals a highly non-uniform structure caused by the action of Kelvin-Helmholtz instabilities that originate at the fireball-torus interface. Large radial variations of the baryon density (up to several orders of magnitude) are uncorrelated with moderate variations of the Lorentz factor (factors of a few) and fluctuations of the gently declining radiation-dominated pressure. In the angular direction the Lorentz factor reveals a nearly flat plateau-like maximum with values of several hundreds, that can be located up to 7° off the symmetry axis, and a steep decrease to less than 10 for polar angles larger than 15°-20°. Lateral expansion of the ultrarelativistic core of the flow is prevented by a subsonic velocity component of about 0.05c towards the symmetry axis, whereas the moderately relativistic wings show a subsonic sideways inflation with less than 0.07c (measured in the frame comoving with the radial flow). Title: Relativistic MHD simulations of extragalactic jets Authors: Leismann, T.; Antón, L.; Aloy, M. A.; Müller, E.; Martí, J. M.; Miralles, J. A.; Ibáñez, J. M. Bibcode: 2005A&A...436..503L Altcode: We have performed a comprehensive parameter study of the morphology and dynamics of axisymmetric, magnetized, relativistic jets by means of numerical simulations. The simulations have been performed with an upgraded version of the GENESIS code which is based on a second-order accurate finite volume method involving an approximate Riemann solver suitable for relativistic ideal magnetohydrodynamic flows, and a method of lines. Starting from pure hydrodynamic models we consider the effect of a magnetic field of increasing strength (up to β ≡ |b|2/2p ≈ 3.3 times the equipartition value) and different topology (purely toroidal or poloidal). We computed several series of models investigating the dependence of the dynamics on the magnetic field in jets of different beam Lorentz factor and adiabatic index. We find that the inclusion of the magnetic field leads to diverse effects which contrary to Newtonian magnetohydrodynamics models do not always scale linearly with the (relative) strength of the magnetic field. The relativistic models show, however, some clear trends. Axisymmetric jets with toroidal magnetic fields produce a cavity which consists of two parts: an inner one surrounding the beam which is compressed by magnetic forces, and an adjacent outer part which is inflated due to the action of the magnetic field. The outer border of the outer part of the cavity is given by the bow-shock where its interaction with the external medium takes place. Toroidal magnetic fields well below equipartition (β = 0.05) combined with a value of the adiabatic index of 4/3 yield extremely smooth jet cavities and stable beams. Prominent nose cones form when jets are confined by toroidal fields and carry a high Poynting flux (σ≡ |b|2/ρ>0.01 and β≥ 1). In contrast, none of our models possessing a poloidal field develops such a nose cone. The size of the nose cone is correlated with the propagation speed of the Mach disc (the smaller the speed the larger is the size). If two models differ only by the adiabatic index, jets having smaller adiabatic indices tend to develop smaller nose cones. Title: Producing short GRBs from coalescing compact binaries Authors: Aloy, M. A.; Janka, H. -Th.; Müller, E. Bibcode: 2005NCimC..28..399A Altcode: We present some of the results of a series of relativistic hydrodynamic simulations of compact binary mergers as potential candidates to be progenitors of short gamma-ray bursts. We discuss some of the generic conditions under which a short gamma-ray burst can be initiated in this kind of progenitor and the main characteristics of the resulting outflow. Title: The Parkes H I Survey of the Magellanic System Authors: Brüns, C.; Kerp, J.; Staveley-Smith, L.; Mebold, U.; Putman, M. E.; Haynes, R. F.; Kalberla, P. M. W.; Muller, E.; Filipovic, M. D. Bibcode: 2005A&A...432...45B Altcode: 2004astro.ph.11453B We present the first fully and uniformly sampled, spatially complete HI survey of the entire Magellanic System with high velocity resolution (Δ v = 1.0 km s-1), performed with the Parkes Telescope. Approximately 24 percent of the southern sky was covered by this survey on a ≈5´ grid with an angular resolution of HPBW = 14.1 arcmin. A fully automated data-reduction scheme was developed for this survey to handle the large number of HI spectra (1.5×106). The individual Hanning smoothed and polarization averaged spectra have an rms brightness temperature noise of σ = 0.12 K. The final data-cubes have an rms noise of σrms ≈ 0.05 K and an effective angular resolution of ≈16´. In this paper we describe the survey parameters, the data-reduction and the general distribution of the HI gas. The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are associated with huge gaseous features - the Magellanic Bridge, the Interface Region, the Magellanic Stream, and the Leading Arm - with a total HI mass of M(HI) = 4.87×108 M [d/55 kpc]2, if all HI gas is at the same distance of 55 kpc. Approximately two thirds of this HI gas is located close to the Magellanic Clouds (Magellanic Bridge and Interface Region), and 25% of the HI gas is associated with the Magellanic Stream. The Leading Arm has a four times lower HI mass than the Magellanic Stream, corresponding to 6% of the total HI mass of the gaseous features. We have analyzed the velocity field of the Magellanic Clouds and their neighborhood introducing a LMC-standard-of-rest frame. The HI in the Magellanic Bridge shows low velocities relative to the Magellanic Clouds suggesting an almost parallel motion, while the gas in the Interface Region has significantly higher relative velocities indicating that this gas is leaving the Magellanic Bridge building up a new section of the Magellanic Stream. The Leading Arm is connected to the Magellanic Bridge close to an extended arm of the LMC. The clouds in the Magellanic Stream and the Leading Arm show significant differences, both in the column density distribution and in the shapes of the line profiles. The HI gas in the Magellanic Stream is more smoothly distributed than the gas in the Leading Arm. These morphological differences can be explained if the Leading Arm is at considerably lower z-heights and embedded in a higher pressure ambient medium.

The Parkes Telescope is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. Title: Relativistic Outflows From Remnants of Compact Object Mergers and Their Viability as Progenitors of Short Gamma-ray Bursts Authors: Aloy, M. A.; Janka, T. -H.; Müller, E. Bibcode: 2005tsra.conf...69A Altcode: We summarize the most important results of a series of relativistic hydrodynamic simulations of mergers of compact binaries as potential candidates to be progenitors of short gamma-ray bursts. We discuss some of the generic conditions under which a short gamma-ray burst can be initiated and collimated in this kind of progenitor and the main characteristics of the resulting outflow. We conclude that not every merger will be able to produce a short gamma-ray burst. The generation of a successful event depends on the mass of the halo produced during the process of merging of the system. Due to the lateral structure of the generated ultrarelativistic outflows we expect some degree of variability between observed bursts, depending on the viewing angle relative to the system axis. Such differences will be superimposed on variations due to intrinsic properties of the binary systems and remnant BH-torus systems, e.g., associated with different masses and spins of the merging neutron stars or black holes. Title: Nucleosynthesis in Multi-Dimensional Simulations of SNII Authors: Travaglio, C.; Kifonidis, K.; Müller, E. Bibcode: 2005coex.conf..297T Altcode: 2005IAUCo.192..297T We investigate explosive nuclear burning in core collapse supernovae by coupling a tracer particle method to one- and two-dimensional Eulerian hydrodynamic calculations. Adopting the most recent experimental and theoretical nuclear data, we compute the nucleosynthetic yields for 15 M stars with solar metallicity, by post-processing the temperature and density history of advected tracer particles. We compare our results to 1D calculations published in the literature. Title: HI Observations of High Velocity Clouds Authors: Saucedo-McQuade, K.; Pantoja, C.; Lebron, M.; Muller, E. Bibcode: 2004AAS...20514214S Altcode: 2004BAAS...36.1583S We present the reduced data of selected observations of High Velocity Clouds (HVCs). The data were from previous observations of HVCs made at Arecibo Observatory using L and C band receivers.

For this project, a sample of HVCs was selected from the HI survey by Hartmann and Burton (1997). These HVCs were selected so that they have a strong continuum source near their position. The data was studied for three sources from this survey. These sources were observed using a cross pattern with 12 minutes ON source and 12 minutes OFF source. The OFFs were taken at positions 1 beamwidth away (NS EW) from the continuum source position. The associated absorption line spectra was reduced using available IDL routines and the column densities for HI and formaldehyde data were calculated.

This research was part of the Research Experiences for Undergraduates (REU) Program at Arecibo Observatory. The REU Program is sponsored by the National Science Foundation. Arecibo Observatory is operated by NAIC, Cornell University, under a cooperative agreement with the NSF. Title: Relativistic outflows from remnants of compact ob ject mergers and their viability for short gamma-ray bursts Authors: Aloy, M. A.; Janka, H. -Th; Müller, E. Bibcode: 2004txra.confE...1A Altcode: We summarize the most important results of a series of relativistic hydrodynamic simulations of mergers of compact binaries as potential candidates to be progenitors of short gamma-ray bursts. We discuss some of the generic conditions under which a short gamma-ray burst can be initiated and collimated in this kind of progenitor and the main characteristics of the resulting outflow. We conclude that not every merger will be able to produce a short gamma-ray burst. The generation of a successful event depends on the mass of the halo produced during the process of merging of the system. Due to the lateral structure of the generated ultrarelativistic outflows we expect some degree of variability between observed bursts, depending on the viewing angle relative to the system axis. Such differences will be superimposed on variations due to intrinsic properties of the binary systems and remnant BH-torus systems, e.g., associated with different masses and spins of the merging neutron stars or black holes. Title: A Statistical Investigation of H I in the Magellanic Bridge Authors: Muller, E.; Stanimirović, S.; Rosolowsky, E.; Staveley-Smith, L. Bibcode: 2004ApJ...616..845M Altcode: 2004astro.ph..8259M We present results from two statistical analyses applied to a neutral hydrogen (H I) data set of the nearby tidal bridge in the Magellanic System. Primarily, analyses of the spatial power spectrum suggest that the Magellanic Bridge, historically considered to be a single contiguous feature, may in fact be a projection of two kinematically and morphologically distinct structures. The southern and more obviously turbulent parts appear to show structure organized similarly to the adjacent Small Magellanic Cloud (SMC), while the northern regions are shown to be relatively deficient in large-scale power. The extent of modification to the spatial power index by the velocity fluctuations is also highly variant across these parts of the Bridge. We find again that the northern part appears distinct from the southern part and from the SMC, in that the power spectrum is significantly more affected by slower velocity perturbations. We also probe the rate of spectral variation of the H I by measuring the spectral correlation function over selected regions. The results from this analysis highlight a tendency for the H I spectra within the bright parts of the Bridge to have a more persistent correlation in the east-west direction than in the north-south direction. These results are considered to be quantitative evidence for the tidal processes that are thought to have been active throughout the evolution of the Magellanic Bridge. Title: A Sensitive Study of Absorption by Neutral Hydrogen and Molecular Material in Intermediate and High Velocity clouds. Authors: Pantoja, C.; Lebron, M.; Muller, E. Bibcode: 2004AAS...20514215P Altcode: 2004BAAS...36R1583P We have conducted a sensitive study of the molecular and HI components in gas associated with selected high and intermediate velocity clouds. The Arecibo Telescope was used to measure absorption of bright continuum sources at the HI and H2CO transitions, as well as to map the HI emission of a number of selected clouds. No molecular material was detected in any of the targets, to an rms of ∼8 mK. Absorption by HVCs is uncommon and we show here two HI absorption measurements which were a product of this survey. We find that gas which can be convincingly associated with HVCs shows evidence for a warm and cool component, whereas the high velocity gas found in the periphery of the clouds is generally warm, thermally homogenous and unenriched. Title: The First Steps in the Life of a Short GRB Authors: Aloy, M. -A.; Janka, H. -T.; Müller, E. Bibcode: 2004AIPC..727..380A Altcode: We present some results of relativistic hydrodynamic simulations of post-neutron star merger disks as potential candidates to be progenitors of short gamma-ray bursts. We discuss some of the generic conditions under which a gamma-ray burst can be initiated in this kind of progenitor and the characteristics of the resulting outflow. Title: Study of H I and Star Formation Sites in the Magellanic Bridge Authors: Muller, E.; Staveley-Smith, L.; Zealey, W. Bibcode: 2004IAUS..217..506M Altcode: Tidal features represent an important process for the recycling of matter across extremely large spatial scales. The Magellanic Bridge is the closest gaseous tidal feature to our own Galaxy, and offers an ideal opportunity to study the active processes in such phenomena at high spatial resolutions otherwise unavailable. The neutral hydrogen of the western Magellanic Bridge, has been observed with both the Parkes 64m telescope and ATCA interferometer and the resulting dataset has revealed an extremely complex and chaotic morphology. We discuss these observations here with reference to a variety of analyses: the spatial correlation of apparently expanding HI shells with OB associations and the outcome of sensitive Hα and CO surveys. Title: Global Anisotropies in Supernova Explosions and Pulsar Recoil Authors: Scheck, L.; Plewa, T.; Kifonidis, K.; Janka, H. -Th.; Müller, E. Bibcode: 2004astro.ph..5311S Altcode: We show by two-dimensional and first three-dimensional simulations of neutrino-driven supernova explosions that low (l=1,2) modes can dominate the flow pattern in the convective postshock region on timescales of hundreds of milliseconds after core bounce. This can lead to large global anisotropy of the supernova explosion and pulsar kicks in excess of 500 km/s. Title: Synthetic X-ray light curves of BL Lacs from relativistic hydrodynamic simulations Authors: Mimica, P.; Aloy, M. A.; Müller, E.; Brinkmann, W. Bibcode: 2004A&A...418..947M Altcode: 2004astro.ph..1266M We present the results of relativistic hydrodynamic simulations of the collision of two dense shells in a uniform external medium, as envisaged in the internal shock model for BL Lac jets. The non-thermal radiation produced by highly energetic electrons injected at the relativistic shocks is computed following their temporal and spatial evolution. The acceleration of electrons at the relativistic shocks is parametrized using two different models and the corresponding X-ray light curves are computed. We find that the interaction time scale of the two shells is influenced by an interaction with the external medium. For the chosen parameter sets, the efficiency of the collision in converting dissipated kinetic energy into the observed X-ray radiation is of the order of one percent. Title: Nucleosynthesis in multi-dimensional simulations of SNII Authors: Travaglio, C.; Kifonidis, K.; Müller, E. Bibcode: 2004NewAR..48...25T Altcode: We investigate explosive nuclear burning in core collapse supernovae by coupling a tracer particle method to one- and two-dimensional Eulerian hydrodynamic calculations. Adopting the most recent experimental and theoretical nuclear data, we compute the nucleosynthetic yields for 15 M stars with solar metallicity, by post-processing the temperature and density history of advected tracer particles. We compare our results to one-dimensional calculations published in the literature. Title: Pulsar Recoil by Large-Scale Anisotropies in Supernova Explosions Authors: Scheck, L.; Plewa, T.; Janka, H. -Th.; Kifonidis, K.; Müller, E. Bibcode: 2004PhRvL..92a1103S Altcode: 2003astro.ph..7352S Assuming that the neutrino luminosity from the neutron star core is sufficiently high to drive supernova explosions by the neutrino-heating mechanism, we show that low-mode (l=1,2) convection can develop from random seed perturbations behind the shock. A slow onset of the explosion is crucial, requiring the core luminosity to vary slowly with time, in contrast to the burstlike exponential decay assumed in previous work. Gravitational and hydrodynamic forces by the globally asymmetric supernova ejecta were found to accelerate the remnant neutron star on a time scale of more than a second to velocities above 500 km s-1, in agreement with observed pulsar proper motions. Title: Multi-dimensional Nucleosynthesis Calculations of Type II SNe Authors: Travaglio, C.; Kifonidis, K.; Müller, E. Bibcode: 2004oee..sympE..56T Altcode: 2003astro.ph..5440T We investigate explosive nuclear burning in core collapse supernovae by coupling a tracer particle method to one and two-dimensional Eulerian hydrodynamic calculations. Adopting the most recent experimental and theoretical nuclear data, we compute the nucleosynthetic yields for 15 Modot stars with solar metallicity, by post-processing the temperature and density history of advected tracer particles. We compare our results to 1D calculations published in the literature. Title: A Statistical investigation of HI in the Magellanic Bridge Authors: Muller, E.; Stanimirović, S.; Rosolowsky, E.; Staveley-Smith, L. Bibcode: 2003AAS...20310504M Altcode: 2003BAAS...35.1374M We present results from two statistical structural analyses of the nearby tidal HI Bridge in the Magellanic system. Analyses of the spatial power spectrum suggest that the Magellanic Bridge, historically considered to be a single coherent feature, may in fact be a projection of two kinematically and morphologically distinct structures, possibly representing two arms of the Small Magellanic Cloud (SMC). The more turbulent southern parts of the Bridge appear to show structure organised similarly to the adjacent SMC, while the northern regions are shown to be relatively deficient in a large scale power. The modifications to the spatial power index by velocity fluctuations and the turbulent component are also highly variant across these two regions, where the northern part is significantly more affected by slower velocity perturbations than is the southern part.

We also probe the rate of variation of the HI spectra throughout the Bridge, by measuring the Spectral Correlation over selected subsets. The Spectral correlation algorithm is shown to be more sensitive to low-power structural variations than is the Fourier transformations used for the spatial power spectrum, and the results from this analysis highlight a tendency for the spectra of bright parts of the HI in the Bridge to have a more persistent correlation along a direction towards the Large Magellanic Cloud (LMC) and SMC. We attbribute this arrangement of structure to the large-scale tidal processes active during the evolution of the Magellanic Bridge. Title: Non-spherical core collapse supernovae. I. Neutrino-driven convection, Rayleigh-Taylor instabilities, and the formation and propagation of metal clumps Authors: Kifonidis, K.; Plewa, T.; Janka, H. -Th.; Müller, E. Bibcode: 2003A&A...408..621K Altcode: 2003astro.ph..2239K We have performed two-dimensional simulations of core collapse supernovae that encompass shock revival by neutrino heating, neutrino-driven convection, explosive nucleosynthesis, the growth of Rayleigh-Taylor instabilities, and the propagation of newly formed metal clumps through the exploding star. A simulation of a type II explosion in a 15 Msun blue supergiant progenitor is presented, that confirms our earlier type II models and extends their validity to times as late as 5.5 hours after core bounce. We also study a type Ib-like explosion, by simply removing the hydrogen envelope of the progenitor model. This allows for a first comparison of type II and type Ib evolution. We present evidence that the hydrodynamics of core collapse supernovae beyond shock revival differs markedly from the results of simulations that have followed the Rayleigh-Taylor mixing starting from ad hoc energy deposition schemes to initiate the explosion. We find iron group elements to be synthesized in an anisotropic, dense, low-entropy shell that expands with velocities of ~ 17 000 km s-1 shortly after shock revival. The growth of Rayleigh-Taylor instabilities at the Si/O and (C+O)/He composition interfaces of the progenitor, seeded by the flow-structures resulting from neutrino-driven convection, leads to a fragmentation of this shell into metal-rich ``clumps''. This fragmentation starts already ~ 20 s after core bounce and is complete within the first few minutes of the explosion. During this time the clumps are slowed down by drag, and by the positive pressure gradient in the unstable layers. However, at t ~ 300 s they decouple from the flow and start to propagate ballistically and subsonically through the He core, with the maximum velocities of metals remaining constant at ~ 3500 - 5500 km s-1. This early ``clump decoupling'' leads to significantly higher 56Ni velocities at t = 300 s than in one-dimensional models of the explosion, demonstrating that multi-dimensional effects which are at work within the first minutes, and which have been neglected in previous studies (especially in those which dealt with the mixing in type II supernovae), are crucial. Despite comparably high initial maximum nickel velocities in both our type II and our type Ib-like model, we find that there are large differences in the final maximum nickel velocities between both cases. In the ``type Ib'' model the maximum velocities of metals remain frozen in at ~ 3500 - 5500 km s-1 for t >= 300 s, while in the type II model they drop significantly for t > 1500 s. In the latter case, the massive hydrogen envelope of the progenitor forces the supernova shock to slow down strongly, leaving behind a reverse shock and a dense helium shell (or ``wall'') below the He/H interface. After penetrating into this dense material the metal-rich clumps possess supersonic speeds, before they are slowed down by drag forces to ~ 1200 km s-1 at a time of 20 000 s post-bounce. While, due to this deceleration, the maximum velocities of iron-group elements in SN 1987 A cannot be reproduced in case of the considered 15 Msun progenitor, the ``type Ib'' model is in fairly good agreement with observed clump velocities and the amount of mixing inferred for type Ib supernovae. Thus it appears promising for calculations of synthetic spectra and light curves. Furthermore, our simulations indicate that for type Ib explosions the pattern of clump formation in the ejecta is correlated with the structure of the convective pattern prevailing during the shock-revival phase. This might be used to deduce observational constraints for the dynamics during this early phase of the evolution, and the role of neutrino heating in initiating the explosion. Title: A search for 85.5- and 86.6-GHz methanol maser emission Authors: Ellingsen, S. P.; Cragg, D. M.; Minier, V.; Muller, E.; Godfrey, P. D. Bibcode: 2003MNRAS.344...73E Altcode: 2003astro.ph..5236E We have used the Australia Telescope National Facility Mopra 22-m millimetre telescope to search for emission from the 85.5-GHz 6-2-7-1 E and 86.6-GHz 72-63 A- transitions of methanol. The search was targeted towards 22 star formation regions which exhibit maser emission in the 107.0-GHz 31-40 A+ methanol transition, as well as in the 6.6-GHz 51-60 A+ transition characteristic of class II methanol maser sources. Each of these regions was searched at 85.5 GHz, resulting in five detections, of which one appears to be a newly discovered maser. For the 86.6-GHz transition, observations were made of 18 regions, which yielded two detections, but no new maser sources. This search demonstrates that emission from the 6-2-7-1 E and 72-63 A- transitions is rare. Detection of maser emission from either of these transitions therefore indicates the presence of special conditions, different from those in the majority of methanol maser sources. We have observed temporal variability in the 86.6-GHz emission towards 345.010+1.792, which - along with the very narrow line width - confirms that the emission is a maser in this source.

We have combined our current observations with published data for the 6.6-, 12.1-, 85.5-, 86.6-, 107.0-, 108.8- and 156.6-GHz transitions for comparison with the maser model of Sobolev & Deguchi. Both detections and non-detections are useful for setting limits on the physical conditions in star-forming regions which contain methanol maser emission. This has allowed us to estimate the likely ranges of dust temperature, gas density and methanol column density, both for typical methanol maser sources and for those sources which also show 107.0-GHz emission. The gas temperature can also be estimated for those sources exhibiting masers at 85.5 and/or 86.6 GHz. Title: Simulations of precessing jets Authors: Aloy, M. A.; Marti, J. M.; Ibanez, J. M.; Gomez, J. L.; Agudo, I.; Mueller, E. Bibcode: 2003hsa..conf...23A Altcode: We report on the results of a three-dimensional, relativistic, hydrodynamical simulation of a precessing jet through which a compact blob of matter is set to propagate. We conclude that the morphology of superluminal sources is the result of a complex combination of phase motions, viewing angle selection effects, and non-linear interactions between perturbations and the underlying jet and/or external medium. Title: VizieR Online Data Catalog: Western Magellanic Bridge HI observations (Muller+, 2003) Authors: Muller, E.; Staveley-Smith, L.; Zealey, W.; Stanimirovic, S. Bibcode: 2003yCat..73390105M Altcode: Here we present high spatial and velocity resolution observations of the Magellanic Bridge, conducted with both the Australia Telescope Compact Array (ATCA) and with the Parkes telescope.

ATCA observation of the 21-cm H I line were made over a 7x6deg2 field using the 375-m configuration of the ATCA. These observations were made over three sessions: 1997 April 13, 15-16, 18; 1997 October 9-15; and 2000 January 29-February 2. The ATCA observations were made using a 4-MHz bandwidth, with 1024 channels at a central frequency of 1.420GHz.

Parkes observations were made using the Multibeam receiver on the 64-m Parkes telescope, during 1999 November 2-8. Only the seven inner receivers of the Multibeam array were used, with each beam having a FWHM width of 14.1arcmin. 48 overlapping scans were made in declination, using the on-the-fly mapping mode at 1deg/min in declination. The scans were centred on RA=02h00m, DE=-72{deg}20', and extended 8{deg} in declination and in RA, large enough to fully encompass the area observed with the ATCA.

(1 data file). Title: High-resolution HI observations of the Western Magellanic Bridge Authors: Muller, E.; Staveley-Smith, L.; Zealey, W.; Stanimirović, S. Bibcode: 2003MNRAS.339..105M Altcode: 2002astro.ph.10615M The 21-cm line emission from a 7 × 6 deg2 region east of and adjoining the Small Magellanic Cloud (SMC) has been observed with the Australia Telescope Compact Array and the Parkes telescopes. This region represents the westernmost part of the Magellanic Bridge, a gas-rich tail extending ~14° to the Large Magellanic Cloud. A rich and complex neutral hydrogen (HI) structure containing shells, bubbles and filaments is revealed. On the larger scale, the HI of the Bridge is organized into two velocity components. This bimodality, which appears to originate in the SMC, converges to a single velocity component within the observed region. A census of shell-like structures suggests a shell population with characteristics similar to that of the SMC. The mean kinematic age of the shells is ~6 Myr, in agreement with the SMC shell population, but not with ages of OB clusters populating the Magellanic Bridge, which are approximately a factor of 3 older. In general, the projected spatial correlation of Bridge HI shells with OB associations is poor and as such, there does not appear to be a convincing relationship between the positions of OB associations and that of expanding spherical HI structures. This survey has found only one HI shell that has an identifiable association with a known Hα shell. The origin of the expanding structures is therefore generally still uncertain, although current theories regarding their formation include gravitational and pressure instabilities, high-velocity cloud collisions and ram pressure effects. Title: Detection of carbon monoxide within the Magellanic Bridge Authors: Muller, E.; Staveley-Smith, L.; Zealey, W. J. Bibcode: 2003MNRAS.338..609M Altcode: 2002astro.ph..9523M The Mopra 22-m and SEST 15-m telescopes have been used to detect and partially map a region of 12CO(1-0) line emission within the Magellanic Bridge, a region lying between the Large and Small Magellanic Clouds (LMC and SMC, respectively). The emission appears to be embedded in a cloud of neutral hydrogen, and is in the vicinity of an IRAS source. The CO emission region is found to have a 60 μm/100 μm flux density ratio typical for 12CO(1-0) detections within the SMC, although it has a significantly lower 12CO brightness and velocity width. These suggest that the observed region is of a low metallicity, supporting earlier findings that the Magellanic Bridge is not as evolved as the SMC and Magellanic Stream, which are themselves of a lower metallicity than the Galaxy. Our observations, along with empirical models based on SMC observations, indicate that the radius of the detected CO region has an upper limit of ~16 pc. This detection is, to our knowledge, the first detection of CO emission from the Magellanic Bridge and is the only direct evidence of star formation through molecular cloud collapse in this region. Title: C and O Explosive Nucleosynthesis in SNII coupled to Multidimensional Hydrodynamics Authors: Travaglio, C.; Kifonidis, K.; Müller, E. Bibcode: 2003ASPC..304..352T Altcode: 2003cnou.conf..352T No abstract at ADS Title: Characteristic Numerical Relativity Applied to Hydrodynamic Studies of Neutron Stars Authors: Siebel, F.; Font, J. A.; Müller, E.; Papadopoulos, P. Bibcode: 2002nmgm.meet.1719S Altcode: We present tests and results of a new axisymmetric, fully general relativistic code with a perfect fluid matter field. Our implementation is based on the null cone formalism of Bondi [2] and Tamburino-Winicour [14,15]. 3D characteristic numerical relativity has been proven to be very stable and accurate for evolutions of black hole spacetimes [7]. Following previous work [8,1] we solve the Einstein equation for a stress-energy tensor of a perfect fluid in characteristic coordinates. The evolution of the matter fields is performed using relativistic high-resolution shock-capturing schemes [4,11,13] based upon Riemann solvers. The implementation of such schemes in a 3D characteristic code is the current subject of a collaboration (GRACE). In this work we restrict ourselves to axisymmetric spacetimes, building on the vacuum code of Gómez, Papadopoulos and Winicour [6]. Applications in spherical symmetry have been presented in [11,12,9]... Title: Numerical Studies of Rotational Core Collapse in Axisymmetry Using the Conformally Flat Metric Approach Authors: Dimmelmeier, H.; Font, J. A.; Müller, E. Bibcode: 2002nmgm.meet.1695D Altcode: Numerical simulations of matter flows evolving in the presence of strong (and dynamic) gravitational fields are a highly complex problem. In order to simplify the complexity of the gravitational field equations of general relativity, Wilson and coworkers proposed an approximation scheme, where the 3-metric γij is chosen to be conformally fiat, which reduces the Einstein equations to a set of 5 coupled elliptic equations. In this paper we present an axisymmetric general relativistic hydrodynamic code which is based upon this approach, and utilizes high-resolution shock-capturing schemes to solve the hydrodynamic equations. We report on preliminary applications of the code to rotating neutron stars and supernova core collapse in axisymmetry. These results demonstrate the feasibility of the code to handle a variety of relativistic astrophysical situations. The code will be used in the near future to obtain information about gravitational radiation from rotating gravitational collapse. Title: Relativistic simulations of rotational core collapse II. Collapse dynamics and gravitational radiation Authors: Dimmelmeier, H.; Font, J. A.; Müller, E. Bibcode: 2002A&A...393..523D Altcode: 2002astro.ph..4289D We have performed hydrodynamic simulations of relativistic rotational supernova core collapse in axisymmetry and have computed the gravitational radiation emitted by such an event. The Einstein equations are formulated using the conformally flat metric approximation, and the corresponding hydrodynamic equations are written as a first-order flux-conservative hyperbolic system. Details of the methodology and of the numerical code have been given in an accompanying paper. We have simulated the evolution of 26 models in both Newtonian and relativistic gravity. The initial configurations are differentially rotating relativistic 4 / 3 -polytropes in equilibrium which have a central density of 1010 g cm-3. Collapse is initiated by decreasing the adiabatic index to some prescribed fixed value. The equation of state consists of a polytropic and a thermal part for a more realistic treatment of shock waves. Any microphysics like electron capture and neutrino transport is neglected. Our simulations show that the three different types of rotational supernova core collapse and gravitational waveforms identified in previous Newtonian simulations (regular collapse, multiple bounce collapse, and rapid collapse) are also present in relativistic gravity. However, rotational core collapse with multiple bounces is only possible in a much narrower parameter range in relativistic gravity. The relativistic models cover almost the same range of gravitational wave amplitudes ( 4 x 10-21 <=h{TT} <=3 x 10-20 for a source at a distance of 10 kpc) and frequencies ( 60 Hz <=nu <=1000 Hz ) as the corresponding Newtonian ones. Averaged over all models, the total energy radiated in the form of gravitational waves is 8.2 x 10-8 Msun c2 in the relativistic case, and 3.6 x 10-8 Msun c2 in the Newtonian case. For all collapse models that are of the same type in both Newtonian and relativistic gravity, the gravitational wave signal is of lower amplitude. If the collapse type changes, either weaker or stronger signals are found in the relativistic case. For a given model, relativistic gravity can cause a large increase of the characteristic signal frequency of up to a factor of five, which may have important consequences for the signal detection. Our study implies that the prospects for detection of gravitational wave signals from axisymmetric supernova rotational core collapse do not improve when taking into account relativistic gravity. The gravitational wave signals obtained in our study are within the sensitivity range of the first generation laser interferometer detectors if the source is located within the Local Group. An online catalogue containing the gravitational wave signal amplitudes and spectra of all our models is available at the URL http://www.mpa-garching.mpg.de/Hydro/hydro.html. Title: Relativistic simulations of rotational core collapse I. Methods, initial models, and code tests Authors: Dimmelmeier, H.; Font, J. A.; Müller, E. Bibcode: 2002A&A...388..917D Altcode: 2002astro.ph..4288D We describe an axisymmetric general relativistic code for rotational core collapse. The code evolves the coupled system of metric and fluid equations using the ADM 3 + 1 formalism and a conformally flat metric approximation of the Einstein equations. Within this approximation the ADM 3 + 1 equations reduce to a set of five coupled non-linear elliptic equations for the metric components. The equations are discretized on a 2D grid in spherical polar coordinates and are solved by means of a Newton-Raphson iteration using a block elimination scheme to solve the diagonally dominant, sparse linear system arising within each iteration step. The relativistic hydrodynamics equations are formulated as a first-order flux-conservative hyperbolic system and are integrated using high-resolution shock-capturing schemes based on Riemann solvers. We assess the quality of the conformally flat metric approximation for relativistic core collapse and present a comprehensive set of tests that the code successfully passed. The tests include relativistic shock tubes, the preservation of the rotation profile and of the equilibrium of rapidly and differentially rotating neutron stars (approximated as rotating polytropes), spherical relativistic core collapse, and the conservation of rest-mass and angular momentum in dynamic spacetimes. The application of the code to relativistic rotational core collapse, with emphasis on the gravitational waveform signature, is presented in an accompanying paper. Title: Does the plasma composition affect the long-term evolution of relativistic jets? Authors: Scheck, L.; Aloy, M. A.; Martí, J. M.; Gómez, J. L.; Müller, E. Bibcode: 2002MNRAS.331..615S Altcode: 2001astro.ph.11369S We study the influence of the matter content of extragalactic jets on their morphology, dynamics and emission properties. For this purpose we consider jets of extremely different compositions, including pure leptonic and baryonic plasmas. Our work is based on two-dimensional relativistic hydrodynamic simulations of the long-term evolution of powerful extragalactic jets propagating into a homogeneous environment. The equation of state used in the simulations accounts for an arbitrary mixture of electrons, protons and electron-positron pairs. Using the hydrodynamic models, we have also computed synthetic radio maps and the thermal bremsstrahlung X-ray emission from their cavities. Although there is a difference of about three orders of magnitude in the temperatures of the cavities inflated by the simulated jets, we find that both the morphology and the dynamic behaviour are almost independent of the assumed composition of the jets. Their evolution proceeds in two distinct epochs. During the first one, multidimensional effects are unimportant and the jets propagate ballistically. The second epoch starts when the first larger vortices are produced near the jet head, causing the beam cross-section to increase and the jet to decelerate. The evolution of the cocoon and cavity is in agreement with a simple theoretical model. The beam velocities are relativistic (Γ ~=4) at kiloparsec scales, supporting the idea that the X-ray emission of several extragalactic jets may be due to relativistically boosted CMB photons. The radio emission of all models is dominated by the contribution of the hotspots. All models exhibit a depression in the X-rays surface brightness of the cavity interior, in agreement with recent observations. Title: Gravitational waves from relativistic rotational core collapse in axisymmetry Authors: Dimmelmeier, H.; Font, J. A.; Müller, E. Bibcode: 2002CQGra..19.1291D Altcode: We present results from simulations of axisymmetric relativistic rotational core collapse. The main objective of our investigation is to compute the waveforms of gravitational radiation emitted in such events, extending previous Newtonian simulations to relativity. The general relativistic hydrodynamic equations are formulated in flux-conservative form and solved using a high-resolution shock-capturing scheme. The Einstein equations are solved assuming a conformally flat 3-metric and the quadrupole formula is used to extract waveforms of the gravitational radiation emitted during the collapse. A comparison of our results with those of Newtonian simulations shows that gravitational wave amplitudes agree within 30%. Surprisingly, in some cases, relativistic effects actually diminish the amplitude of the gravitational wave signal. We further find that the parameter range of models suffering multiple coherent bounces due to centrifugal forces is considerably smaller than in Newtonian simulations. Title: Gravitational waves from rotational core collapse in the conformally flat spacetime approximation Authors: Dimmelemeier, H.; Font, J. A.; Müller, E. Bibcode: 2001AIPC..586..757D Altcode: 2001tsra.conf..757D We have developed an axisymmetric general relativistic hydrodynamic code based upon an approximation scheme recently proposed by Wilson and coworkers, in which the 3-metric γij is conformally flat, thus reducing the mathematical complexity of the Einstein metric equations to a set of 5 coupled elliptic equations. Applications of our code to rotational supernova core collapse are presented. We also discuss first results concerning the emission of gravitational waves. . Title: Spherical collapse of supermassive stars: Neutrino emission and gamma-ray bursts Authors: Linke, F.; Font, J. A.; Janka, H. -T.; Müller, E.; Papadopoulos, P. Bibcode: 2001A&A...376..568L Altcode: 2001astro.ph..3144L We present the results of numerical simulations of the spherically symmetric gravitational collapse of supermassive stars (SMS). The collapse is studied using a general relativistic hydrodynamics code. The coupled system of Einstein and fluid equations is solved employing coordinates adapted to a foliation of the spacetime by means of outgoing null hypersurfaces. The code contains an equation of state which includes effects due to radiation, electrons and baryons, and detailed microphysics to account for electron-positron pairs. In addition energy losses by thermal neutrino emission are included. We are able to follow the collapse of SMS from the onset of instability up to the point of black hole formation. Several SMS with masses in the range 5x 105 Msun-109 Msun are simulated. In all models an apparent horizon forms initially, enclosing the innermost 25% of the stellar mass. From the computed neutrino luminosities, estimates of the energy deposition by nu bar nu-annihilation are obtained. Only a small fraction of this energy is deposited near the surface of the star, where, as proposed recently by Fuller & Shi (\cite{Fuller98}), it could cause the ultrarelativistic flow believed to be responsible for gamma -ray bursts. Our simulations show that for collapsing SMS with masses larger than 5x 105 Msun the energy deposition is at least two orders of magnitude too small to explain the energetics of observed long-duration bursts at cosmological redshifts. In addition, in the absence of rotational effects the energy is deposited in a region containing most of the stellar mass. Therefore relativistic ejection of matter is impossible. Title: AMRA: An Adaptive Mesh Refinement hydrodynamic code for astrophysics Authors: Plewa, T.; Müller, E. Bibcode: 2001CoPhC.138..101P Altcode: 2000astro.ph.10626P Implementation details and test cases of a newly developed hydrodynamic code, amra, are presented. The numerical scheme exploits the adaptive mesh refinement technique coupled to modern high-resolution schemes which are suitable for relativistic and non-relativistic flows. Various physical processes are incorporated using the operator splitting approach, and include self-gravity, nuclear burning, physical viscosity, implicit and explicit schemes for conductive transport, simplified photoionization, and radiative losses from an optically thin plasma. Several aspects related to the accuracy and stability of the scheme are discussed in the context of hydrodynamic and astrophysical flows. Title: Non-spherical core collapse supernovae and nucleosynthesis Authors: Kifonidis, K.; Müller, E.; Plewa, T. Bibcode: 2001NuPhA.688..168K Altcode: 2000astro.ph.10085K Motivated by observations of supernova SN 1987A, various authors have simulated Rayleigh-Taylor (RT) instabilities in the envelopes of core collapse supernovae (for a review, see Mueller 1998). The non-radial motion found in these simulations qualitatively agreed with observations in SN 1987A, but failed to explain the extent of mixing of newly synthesized 56Ni quantitatively. Here we present results of a 2D hydrodynamic simulation which re-addresses this failure and covers the entire evolution of the first 5 hours after core bounce. Title: Exploding and non-exploding stars: Coupling nuclear reaction networks to multidimensional hydrodynamics Authors: Kifonidis, K.; Plewa, T.; Müller, E. Bibcode: 2001AIPC..561...21K Altcode: 2001tsnp.symp...21K; 2000astro.ph.11206K After decades of one-dimensional nucleosynthesis calculations, the growth of computational resources has meanwhile reached a level, which for the first time allows astrophysicists to consider performing routinely realistic multidimensional nucleosynthesis calculations in explosive and, to some extent, also in non-explosive environments. In the present contribution we attempt to give a short overview of the physical and numerical problems which are encountered in these simulations. In addition, we assess the accuracy that can be currently achieved in the computation of nucleosynthetic yields, using multidimensional simulations of core collapse supernovae as an example. . Title: On the Crystallization of Small Silica Particles in Circumstellar Environments Authors: John, M.; Müller, E.; Patzer, B.; Lüttke, M.; Sedlmayr, E. Bibcode: 2001AGM....18..P48J Altcode: Infrared Space Observatory (ISO) observations have revealed the presence of crystalline silicate dust in circumstellar environments of some evolved stars (e.g. Waters et al. 1996, A&A 315, L361). Molster et al. (2001, A&A 366, 923), for instance, reported the discovery of a carbon-rich AGB star surrounded by a highly crystalline silicate dust shell as indicated by the high resolution ISO-SWS spectrum. However, it is still a matter of debate, whether the presence of crystalline dust is restricted only to certain phases of the stellar evolution (e.g. Kemper et al. 2000, A&A 369, 132). In order to understand the process, which leads to the formation of crystalline structures in circumstellar environments, the microphysical rearrangement of small silica particles is investigated by means of molecular dynamic calculations. The results indicate a dynamic coexistence of `amorphous'-like and symmetrical, `crystalline' structures. Such rearrangement processes depend on the energy transfer to the grain governed by the physical conditions of the astrophysical environment. Therefore, the effect of the degree of crystallinity on optical properties is additionally exemplified by Mie calculations. Some implications regarding the condensation and the mineralogy of silicate dust particles in the circumstellar environments of AGB and post-AGB objects are discussed. Title: Optimization of a Tunable Quasi-Monochromatic X-ray Source for Cell Irradiations Authors: Neubert, W.; Enghardt, W.; Lehnert, U.; Müller, E.; Naumann, B.; Panteleeva, A.; Pawelke, J. Bibcode: 2001amcr.conf..123N Altcode: No abstract at ADS Title: Fluid Dynamics Authors: Müller, E. Bibcode: 2000eaa..bookE2089M Altcode: Fluid dynamics is a subfield of continuum mechanics which deals with the theory of motion of a fluid (hydrodynamics) or gas (gas dynamics).... Title: Characteristic numerical relativity applied to hydrodynamic studies of neutron stars Authors: Siebel, F.; Font, J. A.; Mueller, E.; Papadopoulos, P. Bibcode: 2000gr.qc....11096S Altcode: We present tests and results of a new axisymmetric, fully general relativistic code capable of solving the coupled Einstein-matter system for a perfect fluid matter field. Our implementation is based on the Bondi metric, by which the spacetime is foliated with a family of outgoing light cones. We use high-resolution shock-capturing schemes to solve the fluid equations. The code can accurately maintain long-term stability of a spherically symmetric, relativistic, polytropic equilibrium model of a neutron star. In axisymmetry, we demonstrate global energy conservation of a perturbed neutron star in a compactified spacetime, for which the total energy radiated away by gravitational waves corresponds to a significant fraction of the Bondi mass. Title: Numerical Simulations of the Precessing Jets of SS433 Authors: Muller, E.; Brinkmann, W. Bibcode: 2000IAUS..195..415M Altcode: The unique Galactic object SS433 contains the best-studied relativistic jets, and their physical parameters (velocity, temperature, density) are known to an astronomically unprecedented accuracy, i.e., to factors of order unity. The comparison of numerical simulations of these jets with observations provides deeper insight into the SS433/W50 system and is ideal for testing our understanding of the jet phenomenon in general. Title: Relativistic Jets from Collapsars Authors: Aloy, M. A.; Müller, E.; Ibáñez, J. M.; Martí, J. M.; MacFadyen, A. Bibcode: 2000ApJ...531L.119A Altcode: 1999astro.ph.11098A Using a collapsar progenitor model of MacFadyen & Woosley, we have simulated the propagation of an axisymmetric jet through a collapsing rotating massive star with the GENESIS multidimensional relativistic hydrodynamic code. The jet forms as a consequence of an assumed (constant or variable) energy deposition in the range of 1050-1051 ergs s-1 within a 30 deg cone around the rotation axis. The jet flow is strongly beamed (approximately less than a few degrees), spatially inhomogeneous, and time dependent. The jet reaches the surface of the stellar progenitor (R*=2.98x1010 cm) intact. At breakout, the maximum Lorentz factor of the jet flow is 33. After breakout, the jet accelerates into the circumstellar medium, whose density is assumed to decrease exponentially and then become constant, ρext=10-5 g cm-3. Outside the star, the flow begins to expand laterally also (v~c), but the beam remains very well collimated. At a distance of 2.54 R*, where the simulation ends, the Lorentz factor has increased to 44. Title: Nucleosynthesis and Clump Formation in a Core-Collapse Supernova Authors: Kifonidis, K.; Plewa, T.; Janka, H. -Th.; Müller, E. Bibcode: 2000ApJ...531L.123K Altcode: 1999astro.ph.11183K High-resolution two-dimensional simulations were performed for the first 5 minutes of the evolution of a core-collapse supernova explosion in a 15 Msolar blue supergiant progenitor. The computations start shortly after bounce and include neutrino-matter interactions by using a lightbulb approximation for the neutrinos and a treatment of the nucleosynthesis due to explosive silicon and oxygen burning. We find that newly formed iron-group elements are distributed throughout the inner half of the helium core by Rayleigh-Taylor instabilities at the (Ni + Si)/O and (C + O)/He interfaces, seeded by convective overturn during the early stages of the explosion. Fast-moving nickel mushrooms with velocities up to ~4000 km s-1 are observed. This offers a natural explanation for the mixing required in light-curve and spectral synthesis studies of Type Ib explosions. A continuation of the calculations to later times, however, indicates that the iron velocities observed in SN 1987A cannot be reproduced because of a strong deceleration of the clumps in the dense shell left behind by the shock at the He/H interface. Title: Two-dimensional versus Three-dimensional Supernova Hydrodynamic Instability Growth Authors: Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.; Bazán, G.; Müller, E.; Fryxell, B. A.; Teyssier, R. Bibcode: 2000ApJ...528..989K Altcode: Numerical simulations using the SN hydrodynamics code PROMETHEUS are carried out to study the difference between growth of two-dimensional versus three-dimensional single-mode perturbations at the He-H and O-He interfaces of SN 1987A. We find that in the rest frame of an unperturbed one-dimensional interface, a three-dimensional single-mode perturbation grows ~30%-35% faster than a two-dimensional single-mode perturbation, when the wavelengths are chosen to give the same linear stage growth in the planar limit. In simulations where we impose single-mode density perturbations in the O layer of the initial model and random velocity perturbations in the postshock fluid near the He-H interface, we find that both axisymmetric O spikes and three-dimensional O spikes penetrate significantly further than two-dimensional O spikes. The difference between two dimensions and three dimensions predicted by our calculations is not enough to account for the difference between observed 56Co velocities in SN 1987A and the results of previous two-dimensional simulations of SN 1987A, but our results suggest that the real three-dimensional hydrodynamics are noticeably different than the two-dimensional simulations predict. Title: The First Hours of a Core Collapse Supernova Authors: Kifonidis, K.; Plewa, T.; Janka, H. -Th.; Müller, E. Bibcode: 2000nuas.conf...60K Altcode: 2000astro.ph..7282K New two-dimensional, high-resolution calculations of a core collapse supernova in a 15 Msol blue supergiant are presented, which cover the entire evolution from shock revival until the first few hours of the explosion. Explosive nucleosynthesis, its dependence upon convective mixing during the first second of the evolution and the growth of Rayleigh-Taylor instabilities at the composition interfaces of the progenitor star are all modeled consistently and allow for a comparison with observational data. We confirm our earlier findings, that the perturbations induced by neutrino driven convection are sufficiently strong to seed large-scale Rayleigh-Taylor mixing and to destroy the onion-shell structure of the stellar He-core. As in our earlier calculations, the strong deceleration of the nickel clumps in the layers adjacent to the He/H interface suggests that the high velocities of iron-group elements observed in SN 1987A cannot be explained on the basis of currently favored progenitor models. Possible solutions to this dilemma and the implications of the mixing for type Ib explosions are briefly discussed. Title: The First Five Minutes of a Core Collapse Supernova: Multidimensional Hydrodynamic Models Authors: Kifonidis, K.; Plewa, T.; Janka, H. -Th.; Mueller, E. Bibcode: 1999astro.ph.11407K Altcode: We present results of high-resolution two-dimensional simulations which follow the first five minutes of a core collapse supernova explosion in a 15 solar mass blue supergiant progenitor. The computations start shortly after core bounce and include neutrino-matter interactions by using a light-bulb approximation for the neutrinos, and a treatment of the nucleosynthesis due to explosive silicon and oxygen burning. We find that newly formed iron-group elements are distributed throughout a significant fraction of the stellar helium core by the concerted action of convective and Rayleigh-Taylor instabilities. Fast moving nickel mushrooms with velocities up to 4000 km/s are observed. A continuation of the calculations to later times, however, indicates, that the iron velocities observed in SN 1987 A cannot be reproduced due to a strong deceleration of the clumps during their interaction with the dense shell left behind by the shock at the He/H interface. Therefore, we cannot confirm the claim that convective "premixing" of the nickel in the early phases of the explosion solves the problem of the high iron velocities. Title: An exact Riemann Solver for multidimensional special relativistic hydrodynamics Authors: Pons, J.; Marti, J. Ma.; Muller, E. Bibcode: 1999astro.ph.10462P Altcode: We have generalised the exact solution of the Riemann problem in special relativistic hydrodynamics for arbitrary tangential flow velocities. The solution is obtained by solving the jump conditions across shocks plus an ordinary differential equation arising from the self-similarity condition along rarefaction waves, in a similar way as in purely normal flow. The dependence of the solution on the tangential velocities is analysed. This solution has been used to build up an exact Riemann solver implemented in a multidimensional relativistic (Godunov-type) hydro-code. Title: High-Resolution Three-dimensional Simulations of Relativistic Jets Authors: Aloy, M. A.; Ibáñez, J. M.; Martí, J. M.; Gómez, J. -L.; Müller, E. Bibcode: 1999ApJ...523L.125A Altcode: 1999astro.ph..6428A We have performed high-resolution three-dimensional simulations of relativistic jets with beam-flow Lorentz factors of up to 7, a spatial resolution of 8 cells per beam radius, and up to 75 normalized time units in order to study the morphology and dynamics of three-dimensional relativistic jets. Our simulations show that the coherent fast backflows found in axisymmetric models are not present in three-dimensional models. We further find that when the jet is exposed to nonaxisymmetric perturbations, (1) it does not display the strong perturbations found for three-dimensional classical hydrodynamic and MHD jets (at least during the period of time covered by our simulations) and (2) it does propagate according to the one-dimensional estimate. Small three-dimensional effects in the relativistic beam give rise to a lumpy distribution of apparent speeds like that observed in M87. The beam is surrounded by a boundary layer of high specific internal energy. The properties of this layer are briefly discussed. Title: GENESIS: A High-Resolution Code for Three-dimensional Relativistic Hydrodynamics Authors: Aloy, M. A.; Ibáñez, J. M.; Martí, J. M.; Müller, E. Bibcode: 1999ApJS..122..151A Altcode: 1999astro.ph..3352A The main features of a three-dimensional, high-resolution special relativistic hydro code based on relativistic Riemann solvers are described. The capabilities and performance of the code are discussed. In particular, we present the results of extensive test calculations that demonstrate that the code can accurately and efficiently handle strong shocks in three spatial dimensions. Results of the performance of the code on single and multiprocessor machines are given. Simulations (in double precision) with <=7×106 computational cells require less than 1 Gbyte of RAM memory and ~7×10-5 CPU s per zone and time step (on a SCI Cray-Origin 2000 with a R10000 processor). Currently, a version of the numerical code is under development, which is suited for massively parallel computers with distributed memory architecture (such as, e.g., Cray T3E). Title: The consistent multi-fluid advection method Authors: Plewa, T.; Müller, E. Bibcode: 1999A&A...342..179P Altcode: 1998astro.ph..7241P Simple modifications for higher-order Godunov-type difference schemes are presented which allow for accurate advection of multi-fluid flows in hydrodynamic simulations. The constraint that the sum of all mass fractions has to be equal to one in every computational zone throughout the simulation is fulfilled by renormalizing the mass fractions during the advection step. The proposed modification is appropriate for any difference scheme written in conservation form. Unlike other commonly used methods it does not violate the conservative character of the advection method. A new steepening mechanism, which is based on modification of interpolation profiles, is used to reduce numerical diffusion across composition discontinuities. Additional procedures are described, which are necessary to enforce monotonicity. Several numerical experiments are presented which demonstrate the capability of our Consistent Multi-fluid Advection (CMA) method in case of smooth and discontinuous distributions of fluid phases and under different hydrodynamic conditions. It is shown that due to the reduced diffusivity of the proposed scheme the abundance of some heavy elements obtained from hydrodynamic simulations of type II supernova explosions can change by a factor of a few in the most extreme cases. Title: Book Review: Computational methods for astrophysical fluid flow / Springer Verlag, 1998 Authors: Leveque, R. J.; Mihalas, D.; Dorfi, E. A.; Müller, E. Bibcode: 1999IrAJ...26...73L Altcode: No abstract at ADS Title: Multi-Dimensional Numerical Simulations of Core-Collapse Supernovae Authors: Kifonidis, Konstantinos; Plewa, T.; Janka, H. -Th.; Mueller, E. Bibcode: 1999asra.conf..141K Altcode: No abstract at ADS Title: Simulations of non-axisymmetric rotational core collapse Authors: Rampp, M.; Mueller, E.; Ruffert, M. Bibcode: 1998A&A...332..969R Altcode: 1997astro.ph.11122R We report on the first three-dimensional hydrodynamic simulations of secular and dynamical non-axisymmetric instabilities in collapsing, rapidly rotating stellar cores which extend well beyond core bounce. The resulting gravitational radiation has been calculated using the quadrupole approximation. We find that secular instabilities do not occur during the simulated time interval of several 10ms. Models which become dynamically unstable during core collapse show a strong nonlinear growth of non-axisymmetric instabilities. Both random and coherent large scale initial perturbations eventually give rise to a dominant bar-like deformation (+/- imphi with m=2). In spite of the pronounced tri-axial deformation of certain parts of the core no considerable enhancement of the gravitational radiation is found. This is due to the fact that rapidly rotating cores re-expand after core bounce on a dynamical time scale before non-axisymmetric instabilities enter the nonlinear regime. Hence, when the core becomes tri-axial, it is no longer very compact. Title: Explosive Nucleosynthesis: Coupling Reaction Networks to Amr Hydrodynamics Authors: Kifonidis, K.; Plewa, T.; Müller, E. Bibcode: 1998nuas.conf...25K Altcode: 1998astro.ph..5158K In recent years the technique of Adaptive Mesh Refinement (AMR) has been successfully applied to several astrophysical problems. This method should also allow a consistent multi-dimensional modelling of supernova explosions. In this contribution we address some of the computational difficulties encountered when trying to apply the AMR method to explosive nucleosynthesis and supernova envelope ejection. Title: The Precessing Jets of SS433 Authors: Brinkmann, W.; Müller, E. Bibcode: 1998ajop.conf..211B Altcode: No abstract at ADS Title: Convection in newly born neutron stars Authors: Keil, W.; Janka, H. -T.; Müller, E. Bibcode: 1998sese.conf..557K Altcode: No abstract at ADS Title: Gravitational Radiation from Core Collapse Supernovae Authors: Müller, E. Bibcode: 1998grwa.conf...48M Altcode: No abstract at ADS Title: Convection in protoneutron stars. Authors: Keil, W.; Janka, H. -T.; Müller, E. Bibcode: 1998tsra.conf..717K Altcode: Convectively enhanced neutrino (ν) luminosities from the protoneutron star (PNS) can provide an essential condition for a Type-II supernova explosion. Very recent two-dimensional, self-consistent, general relativistic simulations of the cooling of a newly-formed neutron star demonstrate and confirm the possibility that quasi-Ledoux convection, driven by negative lepton number and entropy gradients, may encompass the whole PNS within less than 1 s and can lead to an increase of the neutrino fluxes by up to a factor of two. Title: Convection in Protoneutron Stars Authors: Müller, E. Bibcode: 1998tsra.conf..717M Altcode: No abstract at ADS Title: The Long Term Evolution of Powerful Relativistic Jets Authors: Martí, J. M.; Müller, E.; Ibañez, J. M. Bibcode: 1998ajop.conf..149M Altcode: No abstract at ADS Title: Supernova hydrodynamics experiments on the Nova laser Authors: Kane, J.; Arnett, D.; Remington, B. A.; Glendinning, S. G.; Rubenchik, A.; Drake, R. P.; Fryxell, B. A.; Muller, E. Bibcode: 1997AAS...191.3911K Altcode: 1997BAAS...29.1266K The critical roles of hydrodynamic instabilities in SN 1987A and in ICF are well known; 2D-3D differences are important in both areas. In a continuing project at Lawrence Livermore National Laboratory (LLNL), the Nova Laser is being used in scaled laboratory experiments of hydrodynamic mixing under supernova-relevant conditions. Numerical simulations of the experiments are being done, using LLNL hydro codes, and astrophysics codes used to model supernovae. Initial investigations with two-layer planar packages having 2D sinusoidal interface perturbations are described in Ap.J. 478, L75 (1997). Early-time simulations done with the LLNL 1D radiation transport code HYADES are mapped into the 2D LLNL code CALE and into the multi-D supernova code PROMETHEUS. Work is underway on experiments comparing interface instability growth produced by 2D sinusoidal versus 3D cross-hatch and axisymmetric cylindrical perturbations. Results of the simulations will be presented and compared with experiment. Implications for interpreting supernova observations and for supernova modelling will be discussed. * Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48. Title: Rapidly rotating stars with either H burning or He burning core. Authors: Shindo, M.; Hashimoto, M.; Eriguchi, Y.; Mueller, E. Bibcode: 1997A&A...326..177S Altcode: We have succeeded in constructing structures of realistic models for rapidly rotating inhomogeneous stars in the nuclear burning stages. The nuclear reaction networks both for CNO cycle and for helium burning have been successfully included in the 2D numerical code. Concerning the equation of state and the opacity, we have used the same ones as used in calculations of spherical stellar structures. The rotation law in our computations covers uniform rotation and differential rotation with rapidly rotating cores. We have computed several equilibrium sequences of massive stars up to models just before the mass begins to shed from the equatorial surface (critical models). We mainly discuss two critical sequences of models: 1) 18Msun_ stars with hydrogen burning cores and 2) 5Msun_ helium stars with helium burning cores. It is found that the effect of rotation on the structure is similar for both sequences. For uniformly rotating hydrogen burning stars the luminosity decrease is about 6.4% which is consistent with the results obtained by other authors. For models which have the angular momentum distribution concentrated toward the center, we get very flattened shapes of stellar surfaces. Compared with the non-rotating models, decrease of the luminosity is found to be 16% for the critical models if the total angular momentum is less than 10^53^g.cm^2^/s and if a toroid-like structure of the density distribution does not appear. On the other hand, decrease of the luminosity becomes significant for stars with the toroid-like structure of the density distribution, i.e. for toroidal distribution of the energy source. It is remarkable that stars whose ratio of the polar radius to the equatorial radius is less than 0.25 have extended envelopes due to a delicate balance between the gravitational force and the centrifugal force. Title: Gravitational radiation from core-collapse supernovae Authors: Müller, E. Bibcode: 1997CQGra..14.1455M Altcode: No abstract at ADS Title: Morphology and Dynamics of Relativistic Jets Authors: Martí, J. M.; Müller, E.; Font, J. A.; Ibáñez, J. M. Z.; Marquina, A. Bibcode: 1997ApJ...479..151M Altcode: We present a comprehensive analysis of the morphology and dynamics of relativistic pressure-matched axisymmetric jets. The numerical simulations have been carried out with a high-resolution shock-capturing hydrocode based on an approximate relativistic Riemann solver derived from the spectral decomposition of the Jacobian matrices of relativistic hydrodynamics. We discuss the dependence of the jet morphology on several parameters, paying special attention to the relativistic effects caused by high Lorentz factors and large internal energies of the beam flow. The parameter space of our analysis is spanned by the ratio of the beam and ambient medium rest mass density (η), the beam Mach number (Mb), the beam Lorentz factor (Wb), and the adiabatic index (γ) of the equation of state (assuming an ideal gas). Both the ultrarelativistic regime (Wb >= 20) and the hypersonic regime (relativistic Mach number greater than 100) have been studied.

Our results show that the enhancement of the effective inertial mass of the beam due to relativistic effects (through the specific enthalpy and the Lorentz factor) makes relativistic jets significantly more stable than Newtonian jets. We find that relativistic jets propagate very efficiently through the ambient medium, at speeds that agree very well with those obtained from an estimate based on a one-dimensional momentum balance. The propagation efficiency of a relativistic jet is an increasing function of the beam flow velocity.

Relativistic jets seem to give rise to two different morphologies, according to the relevance of relativistic effects. Hot beams (i.e., with internal energies comparable to the beam rest-mass energy) show little internal structure (as they are almost in pressure equilibrium with their surroundings) and relatively smooth cocoons forming lobes near the head of the jet. Highly supersonic models, in which the kinematic relativistic effects due to high beam flow Lorentz factors dominate, display extended cocoons that are overpressured with respect to the environment. The cocoon thickness decreases, and its mean pressure increases with increasing beam Lorentz factor. Title: Dynamics and gravitational wave signature of axisymmetric rotational core collapse. Authors: Zwerger, T.; Mueller, E. Bibcode: 1997A&A...320..209Z Altcode: We have carried out a comprehensive parameter study of the dynamics of rotational core collapse in massive stars. The iron cores have been approximated by axisymmetric rotating {GAMMA}=4/3 polytropes in rotational equilibrium. Any transport effects by neutrinos have been neglected. We have computed 18 initial models which differ by their amount of rotational energy and their distribution of angular momentum. The initial models range from slowly to rapidly rotating and from rigidly to extremely differentially rotating configurations. The collapse was induced by suddenly reducing the adiabatic index {GAMMA} to a value {GAMMA}_r_ with 1.28<={GAMMA}_r_<=1.325. The stiffening of the equation of state at nuclear matter density and the thermal pressure in the matter heated by the prompt shock was simulated by means of a simplified analytic equation of state consisting of a polytropic and a thermal part. The evolution of a total of 78 models was followed well beyond core bounce using a two dimensional Newtonian hydrodynamic finite difference code. A subset of models suffers a bounce caused by centrifugal forces at sub-nuclear densities. For a given rotation rate the bounce density decreases with increasing {GAMMA}_r_ and with increasing degree of differential rotation. Models suffering a bounce due to (or mainly due to) centrifugal forces show large amplitude oscillations of the inner core the central density varying by more than a factor of ten. In several models the rotation rate exceeds the critical value, where MacLaurin spheroids become secularly unstable against tri-axial perturbations. Two of the most differentially and rapidly rotating models reach ({GAMMA}_r_=1.30) and even exceed ({GAMMA}_r_=1.28) the critical value for axisymmetric dynamical stability. We have also computed the gravitational (quadrupole) wave signal emitted by our core collapse models. We find both type I (spike + ring-down) and type II (several distinct spikes) gravitational wave signals. Which type occurs is solely determined by the adiabatic index. Signals of type I are produced by models with a "soft" equation of state ({GAMMA}_r_<~1.31), while signals of type II require a "stiff" equation of state ({GAMMA}_r_>1.32). Decreasing the adiabatic index from 1.325 to 1.28 and keeping the other model parameters fixed, we observe a smooth transformation of the signal type. For {GAMMA}_r_=1.28 a third signal type is observed, which shows a large positive and a smaller negative wave amplitude just before and after bounce. Signals of type III are not found for extremely differentially rotating initial models. The energy spectra cover a frequency range of 50Hz<~ν<~3kHz, but most of the power is emitted between 500Hz and 1kHz. Models bouncing at sub-nuclear densities have spectra, which drop extremely rapidly above 1kHz, and models with a type II wave signal have spectra, which show characteristic oscillations. These oscillations vanish when the signal type changes to type I. The spectra are neither very sensitive to the rotation rate nor to the degree of differential rotation. The total amount of energy radiated in form of gravitational waves lies in the range 6x10^-11^Msun_c^2^<~E_GW_<~8x10^-8^Msun_c^2^. The corresponding dimensionless wave amplitudes are in the range 4x10^-25^<~h<~4x10^-23^ for a source at a distance of 10 Mpc. The largest signals are either produced by models which are initially slowly rotating and have an adiabatic index {GAMMA}_r_>=1.32, or which are initially rapidly and strongly differentially rotating and have a relatively small adiabatic index ({GAMMA}_r_<=1.30). Title: 3-D Time Dependent Hydrodynamic Simulations of the Processing Jets of SS433 Authors: Müller, E.; Brinkmann, W. Bibcode: 1997xisc.conf..455M Altcode: No abstract at ADS Title: Gravitational radiation from convective instabilities in Type II supernova explosions. Authors: Mueller, E.; Janka, H. -T. Bibcode: 1997A&A...317..140M Altcode: We present two- and three-dimensional simulations of convective instabilities during the first second of a Type II supernova explosion. Convective overturn occurs in two distinct, spatially well separated regions: (i) inside the proto-neutron star immediately below the neutrinosphere (r<~50km) and (ii) in the neutrino-heated "hot-bubble" region interior to the outward propagating revived shock wave (100km<~r<~1000km). We have calculated the gravitational wave signature of both convective instabilities including the quadrupole waveforms, the energy spectra, and the total amount of the emitted gravitational wave energy. Moreover, we have estimated the amplitude and energy of gravitational waves associated with the anisotropic neutrino emission that is caused by the convective transport of neutrinos and by aspherical perturbations of temperature and density in the neutrinospheric region. For a supernova located at a distance of 10 kpc the maximum dimensionless gravitational wave amplitudes due to convective mass motions range from |h^TT^|=~2x10^-22^ for the three-dimensional simulation to |h^TT^|=~3x10^-21^ for the most strongly radiating two-dimensional model. The total emitted energy varies from 3x10^-14^Msun_c^2^ to 5x10^-10^Msun_c^2^. The convective mass motions inside the proto-neutron star produce a stronger signal than convection in region (ii) with up to a factor of 10 larger amplitudes and 1000 times more gravitational wave energy. Because of smaller convective eddies and structures and slower overturn velocities, the wave amplitudes of three-dimensional models are more than a factor of 10 smaller, and the energy emitted in gravitational waves is almost 3 orders of magnitude less than in the corresponding two-dimensional situation. In two dimensions the gravitational wave amplitude associated with the anisotropic emission of neutrinos can be larger (factor 5) than the wave amplitude due to mass motions in the proto-neutron star, although the energy in the neutrino tidal field is 20 times smaller. In three dimensions the neutrino gravitational wave amplitude is reduced by a factor of about 10 and the gravitational wave energy by a factor of roughly 100 relative to the two-dimensional results. Nevertheless, the neutrino tidal field is more than a factor of 10 larger than the gravitational wave amplitude from mass motions and the corresponding gravitational wave energies can be of similar size. Most of the gravitational radiation from convection inside the proto-neutron star is emitted in the frequency band 100-1000Hz, while convective motions in the hot-bubble region generate waves from several 100Hz down to a few Hz. Gravitational waves from the anisotropic neutrino emission have most power at frequencies between some 10Hz and a few 100Hz and a low-frequency contribution at about 1Hz to several Hz. Features in the gravitational-wave signal from the neutrino-heated region are well correlated with structures in the neutrino signal, both being associated with sinking and rising lumps of matter and with temporal variations of aspherical accretion flows towards the proto-neutron star. A simultaneous measurement of both signals would impose important constraints on the dynamics of Type II supernovae and theoretical models of the explosion mechanism. Title: Gravitational Waves from Core Collapse Supernovae Authors: Müller, E. Bibcode: 1997rggr.conf..273M Altcode: No abstract at ADS Title: Bending Relativistic Jets in AGNs Authors: Plewa, T.; Marti, J. M.; Muller, E.; Rozyczka, M.; Sikora, M. Bibcode: 1997rja..proc..104P Altcode: 1997astro.ph..6124P We present simulations of relativistic jets propagating in a nonuniform medium. Specifically, we study the bending of jets propagating obliquely to the vector of the density-gradient. Our results are applied to the NGC 4258, where such a medium is assumed to be provided by the atmosphere of the sub-parsec accretion disk tilted with respect to the original direction of the jet propagation. As a result, the jet is bent on a scale comparable to the density scaleheight of the disk atmosphere. The magnitude of the bending effect is found to be largest for light jets with low Lorentz factors. The predicted direction of bending is consistent with the observations. Title: Parallelizing a multi-dimensional, explicit, finite difference hydrodynamic code. Authors: Müller, E. Bibcode: 1996AGAb...12..111M Altcode: No abstract at ADS Title: Book reviews Authors: Humphreys, R. M.; Kemp, S.; Savonije, G.; van der Hucht, K. A.; van der Kruit, P. C.; Miley, G.; Bumba, V.; van Nieuwkoop, J.; van Hoolst, T.; Cox, A.; Rutten, R. J.; Kleczek, J.; de Jager, Cornelis; Jerzykiewicz, M.; Zwaan, C.; Poedts, S.; Sakai, Jun-Ichi; Pecker, J. -C.; Heikkila, W.; de Jong, T.; Wilson, P. R.; Müller, E. A.; Hoyng, P.; Icke, V.; Shore, S. N.; Achterberg, A.; Lucchin, F.; Butcher, H.; Ne'Eman, Y.; Heidmann, J.; Belton, M. J. S.; de Graauw, Th.; Waters, L. B. F. M.; Pacini, F.; Hultqvist, B.; Akasofu, S. -I.; Vial, J. -C.; Schatzman, E.; van der Laan, H.; Cole, K. D.; Vanbeveren, D.; Southwood, D.; van der Klis, M.; Katgert, Peter Bibcode: 1996SSRv...76..339H Altcode: No abstract at ADS Title: Neutrino heating, convection, and the mechanism of Type-II supernova explosions. Authors: Janka, H. -T.; Mueller, E. Bibcode: 1996A&A...306..167J Altcode: The role of neutrino heating and convective processes in the explosion mechanism of Type-II supernovae is investigated by one- and two-dimensional hydrodynamical simulations of the long-time evolution of the collapsed stellar core after the bounce at nuclear matter density and after the associated formation of the supernova shock. The parameters describing the neutrino emission from the collapsed stellar core are systematically varied. The possibility to obtain explosions turns out to be very sensitive to the physical conditions in and at the protoneutron star, in particular to its contraction and to the neutrino cooling inside of the gain radius. Yet, above a certain threshold for the core neutrino luminosity, stable and energetic explosions can be obtained in spherical symmetry, provided the energy deposition by neutrinos remains strong for a sufficiently long period. The explosion energy and time scale critically depend on the neutrino fluxes during the shock revival phase and on their temporal decay during the first few 100ms after shock formation. The threshold luminosity is a very sensitive function of the shock stagnation radius, because small radii of the stalled prompt shock lead to significantly higher neutrino loss from the hot and compact postshock layers, cause the region of neutrino heating to be very narrow, and reduce the heating time scale of the matter due to the high infall velocity. Repeating the simulations in two dimensions we find that strong convective processes occur in the collapsed stellar core in two spatially separate regions. One region of convection lies inside the neutrinosphere and another one is located in the neutrino-heated layer below the shock front. The convective mixing around the neutrinosphere is mainly driven by the negative lepton gradient, which is maintained by rapid loss of leptons from the semitransparent layers at the neutrinosphere. This considerably speeds up the deleptonization of the outer layers of the collapsed stellar core. Even 0.5 seconds after bounce a quasi-stationary pattern of convective motion is still present in the protoneutron star. Three-dimensional simulations reveal that rising and sinking convective elements have about half the size as in two dimensions with angular diameters between 10deg and 15deg, which causes corresponding anisotropies of the neutrino emission from the core. The large-scale convective overturn that takes place between the shock and the position of maximum neutrino heating is able to efficiently transport energy from the heated layer into the postshock region. This helps to stabilize the shock revival during the critical phase. It also leads to a faster increase and earlier saturation of the explosion energy, both because neutrino-heated material quickly moves out of the heating region and energy loss by the re-emission of neutrinos is reduced. The overturn pattern shows downflows of matter in narrow flux tubes and rising bubbles with typical angular extensions of 30deg to 60deg (in two dimensions). The material falling towards the neutron star loses lepton number, but readily absorbs energy in the neutrino-heated region, before it rises again. When the explosion gains momentum, this matter is not accreted onto the cooler, neutron-rich protoneutron star any more. After about 200-300ms the convective shell gets decoupled from the heating region and starts to move away from the neutron star to expand in an essentially self-similar way as a thick layer behind the outward propagating shock. The nearly spherically symmetrical "hot-bubble" region begins to develop and turbulence around the protoneutron star ceases. When the supernova shock passes the entropy step of the Si-O-interface about 400-500ms after bounce, the density inversion between the low-density hot-bubble region and the inhomogeneous shell steepens into a strong reverse shock that forms a sharp discontinuity in the neutrino wind from the nascent neutron star. The supernova shock is significantly deformed and velocity, density, temperature, and entropy in the postshock region exhibit large-scale variations with a contrast of up to a factor of 3. This must have consequences for the formation and spatial distribution of nucleosynthesis products and might help to explain the clumpiness, anisotropies, envelope and mantle mixing, and large velocities of iron group nuclei which were observed in the ejecta of SN 1987A and other supernovae. Although in this respect of essential importance, convection in the postshock region does not seem to be indispensable to get successful Type-II explosions via the neutrino-heating mechanism, nor do our simulations allow for the conclusion that its presence inevitably makes the mechanism successful and the explosions very energetic. As in spherical symmetry, the explosion energy and time scale are influenced by the contraction of the cooling neutron star and are very sensitive to the neutrino energy deposition and the size of the neutrino fluxes during a period of several hundred milliseconds after core bounce. Title: Morphology and dynamics of relativistic jets. Authors: Müller, E.; Martí, J. M.; Ibáñez, J. M. Bibcode: 1996AGAb...12...66M Altcode: No abstract at ADS Title: Individual Light Curve FITS of SN IA and H sub 0 Authors: Hoflich, P. A.; Muller, E.; Khokhlov, A. Bibcode: 1996ssr..conf...29H Altcode: 1996IAUCo.145...29H No abstract at ADS Title: Equilibrium structures of self-gravitating disks. Authors: Hashimoto, M.; Eriguchi, Y.; Arai, K.; Müller, E. Bibcode: 1996bpad.conf..269H Altcode: The authors investigate equilibrium structures of rapidly rotating toroids and disks with self-gravity using the two-dimensional code. Two rotational laws are assumed: (1) rotation having constant specific angular momentum (j-const law) and (2) Keplerian rotation. Equilibrium sequences are calculated with the specified central temperature of the toroid and the mass of the central object. Configuration of hot toroids resembles to that of a thick disk. In particular, the central temperature of a toroid exceeds 109K and the luminosity exceeds the Eddington luminosity considerably. It is found that the Keplerian disks with self-gravity have thin, slim, and fat shapes which depend on the distance between the central object and the disk, and also on the mass ratio between the central object and the disk. Title: A Numerical Study of Relativistic Jets Authors: Font, J. A.; Marti, J. M.; Ibanez, J. M.; Muller, E. Bibcode: 1996IAUS..175..435F Altcode: No abstract at ADS Title: Gravitational wave signal of rotational core collapse. Authors: Müller, E.; Zwerger, T. Bibcode: 1996AGAb...12...48M Altcode: No abstract at ADS Title: Morphology and Dynamics of Highly Supersonic Relativistic Jets Authors: Marti, J. M. A.; Muller, E.; Font, J. A.; Ibanez, J. Ma. Bibcode: 1995ApJ...448L.105M Altcode: We present a simulation of a diffuse ( eta = 0.01), high-beam Mach number (Mb = 6.0), relativistic (beam Lorentz factor 22.4) axisymmetric jet, and we discuss its morphology and dynamics. The jet exhibits a prominent structure of oblique shocks inside the beam and possesses an extensive cocoon. This result is qualitatively different from the findings of other recent simulations of low-beam Mach number relativistic jets, where both features are absent. We find that the jet propagates very efficiently through the ambient medium. Its mean velocity is 15 times larger than that expected from classical (i.e., nonrelativistic) simulations. The simulations are performed with a high-resolution shock-capturing scheme using a Riemann solver which is based on the spectral decomposition of the Jacobian matrices of relativistic hydrodynamics. Title: Equilibrium structure of self-gravitating Keplerian disks. Authors: Hashimoto, M.; Eriguchi, Y.; Muller, E. Bibcode: 1995A&A...297..135H Altcode: We present two-dimensional equilibrium models of realistic, self-gravitating Keplerian disks of arbitrary thickness surrounding a gravitating central object (star), which is approximated by a point mass. The point mass and the disk mass of the computed models are in solar units (0.6, 0.39), (0.6, 1.4), (1.4, 0.006), (1.4, 0.011), (3.5, 0.29) and (10.0, 0.28), respectively. The configuration consisting of a central star of 0.6Msun_ and a surrounding disk of 0.39Msun_ is similar to that obtained in the two-dimensional hydrodynamical calculation of Bodenheimer et al. (1991). This shows that we are able to construct equilibrium disk models, which approximate quasi-equilibrium evolutionary stages of accretion disks encountered during proto-star formation. Equilibrium models with a more massive central object, e.g. the (3.5Msun_, 0.29Msun_) model system, can be considered as describing a black hole surrounded by a thick disk, i.e. being representative of systems like SS 433. Title: Neutrino-driven Type-II supernova explosions and the role of convection. Authors: Janka, H. T.; Mueller, E. Bibcode: 1995PhR...256..135J Altcode: The role of neutrino heating and convection in the explosions of Type-II supernovae is reviewed. The neutrino-driven mechanism of supernova explosions is based upon the fact that high-energetic neutrinos streaming up from the hotter interior must transfer energy to the cooler layers adjacent to the nascent neutron star. While this energy deposition is unavoidable, there is still controversy about the point whether it is able to drive and power a Type-II supernova event or not. To investigate this question one-dimensional hydrodynamical simulations have been performed for the long-time evolution of the collapsed stellar core after the bounce at nuclear matter density and after the associated formation of the supernova shock. In these studies the parameters describing the neutrino emission have been varied and the influence of the temporal contraction of the central part of the nascent neutron star has been tested. Title: SN Ia: Light Curves, Spectra,and H0. Authors: Höflich, P.; Dominik, C.; Khokhlov, A.; Muller, E.; Wheeler, J. C. Bibcode: 1995NYASA.759..348H Altcode: No abstract at ADS Title: Instabilitäten und Mischungsvorgänge in Supernovaexplosionen vom Typ II. Computersimulationen einer kosmischen Katastrophe. Authors: Müller, E. Bibcode: 1995S&W....34..350M Altcode: No abstract at ADS Title: Neutron star recoils from anisotropic supernovae. Authors: Janka, H. -T.; Mueller, E. Bibcode: 1994A&A...290..496J Altcode: Refering to recent hydrodynamical computations (Herant et al. 1992; Janka & Mueller 1993a) it is argued that neutron star kicks up to a few hundred km/s might be caused by a turbulent overturn of the matter between proto-neutron star and supernova shock during the early phase of the supernova explosion. These recoil speeds ("kick velocities") may be of the right size to explain the measured proper motions of most pulsars and do not require the presence of magnetic fields in the star. It is also possible that anisotropic neutrino emission associated with convective processes in the surface layers of the nascent neutron star (Burrows & Fryxell 1992; Janka & Mueller 1993b; Mueller 1993) provides an acceleration mechanism (Woosley 1987), although our estimates indicate that the maximum attainable velocities are around 200km/s. Yet, it turns out to be very unlikely that the considered stochastic asymmetries of supernova explosions are able to produce large enough recoils to account for pulsar velocities in excess of about 500km/s, which can be found in the samples of Harrison et al. (1993) and Taylor et al. (1993). It is concluded that other acceleration mechanisms have to be devised to explain the fast motion of PSR 2224+65 (transverse speed >=800km/s Cordes et al. 1993) and the high-velocities deduced from associations between supernova remnants and nearby young pulsars (e.g., Frail & Kulkarni 1991; Stewart et al. 1993; Caraveo 1993). Title: Gamma-Ray Light Curves and Spectra of Models for Type IA Supernovae Authors: Hoeflich, P.; Khokhlov, A.; Mueller, E. Bibcode: 1994ApJS...92..501H Altcode: Based on detailed Monte Carlo calculations, we present γ-ray energy deposition functions, γ-ray light curves, and γ-ray spectra for a large set of theoretical models of Type Ia supernovae including "classical" detonation and deflagration, delayed detonation, explosions of low mass white dwarfs, and tamped detonation scenarios. Our computations show that models for Type Ia supernovae can be discriminated and the absolute amount of ^56^Ni synthesized in the event can be determined on the basis of the γ-ray light curves and spectra if γ-ray measurements are combined with observations at other wavelengths, e.g., in the optical band. We discuss at which times γ-ray observations are most suitable and needed from the theoretical point of view. The implication of the upper limit in the γ-ray flux by CGRO experiment for our understanding of SN 1991T is discussed. We find that this limit is consistent with both the optical light curve and the implied distance (12.5 Mpc) i.e., several models can be ruled out by the γ-ray observations. Title: A comparison of calculated and observed monochromatic type IA supernova light curves. Authors: Mueller, E.; Hoeflich, P. Bibcode: 1994A&A...281...51M Altcode: The calculated monochromatic (B and V) light curves of a set of Type Ia supernova models are compared with the observed monochromatic light curves of 13 Type Ia supernovae (SNIa). The set consists of 11 Type Ia supernova models including deflagrations, detonations, delayed detonations, pulsating delayed detonations and tamped detonations. The theoretical light curves have been calculated using our recently developed light curve model. The model incorporates a detailed equation of state with an elaborate treatment of the ionization balance, an implicit grey LTE radiation transport scheme based on the moment equations, a total energy equation for the gas and the radiation field, expansion opacities, and a Monte Carlo gamma-ray deposition scheme. To evolve the structure of the underlying explosion models homologous expansion is assumed. We find that fast rising light curves (e.g., SN 1972E, SN 1981B and SN 1986G) can be reproduced best by delayed detonation models, and that slowly rising (t_max_ >~ 17 days) light curves (e.g., SN 1984A and SN 1990N) cannot be reproduced by standard detonation, deflagration or delayed detonation models. In order to obtain an acceptable agreement with observations for slowly rising light curves explosion models are required where the C/O white dwarf is surrounded by an unburnt extended envelope of typically 0.2 to 0.4 M_sun_. Our interpretation of the light curves is also favoured from the expansion velocities observed in the spectra of the slowly rising SNIa. Based on a comparison of theoretical light curves and observational data, the distances of the parent galaxies have been determined. We show that SNe Ia allow for a measurement of the value of the Hubble constant provided individual fits are used and if they are located at distances larger than 15 Mpc, because only then they are in the "Hubble" flow. Taking this restriction into account a Hubble constant of H = 66 +/- 10 km/(secMpc) can be derived within a 2σ error. Title: The formation of disk galaxies in a cosmological context: Populations, metallicities and metallicity gradients Authors: Steinmetz, M.; Mueller, E. Bibcode: 1994A&A...281L..97S Altcode: 1993astro.ph.12010S We present first results concerning the metallicities and stellar populations of galaxies formed in a cosmologically motivated simulation. The calculations include dark matter, gas dynamics, radiation processes, star formation, supernovae feed-back, and metal enrichment. A rotating, overdense sphere with a mass of 8 10^11^ M_sun_ serves as initial model. Converging and Jeans unstable regions are allowed to form stars, which get their metallicity from the gas they are formed from. Via supernovae, metal enriched gas is given back to the interstellar medium. The forming galaxy shows the main properties of spiral galaxies: A metal rich bulge, a metal poor stellar halo and a disk of nearly solar composition. Halo and bulge consist predominantly of old stars (> 10.5 Gyrs). The disk has a metallicity gradient of d(log Z)/dr = -0.05 kpc^- 1^, whereas the halo shows none. The models also exhibit a correlation between the metallicity of Pop II stars and the power of small scale fluctuations. The stars of the bulge form from gas which is initially located in the largest maxima of the primordial density fluctuations, whereas the halo stars originate from gas accumulated in less pronounced maxima. Title: Simulation turbulenter Konvektion in Supernova-Explosionen massereicher Sterne. Authors: Janka, H. -T.; Müller, E.; Ruffert, M. Bibcode: 1994stks.book.....J Altcode: Contents: 1. Das Projekt: Numerische Simulation von Typ-II-Supernovae. 2. Die numerischen Verfahren. 3. Die Visualisierung von dreidimensionalen Datensätzen. 4. Die Ergebnisse: Einblick in explodierende Sterne. Title: Galaxy formation in a cluster environment: first steps to a consistent description Authors: Steinmetz, M.; Müller, E. Bibcode: 1994pvgt.conf...34S Altcode: No abstract at ADS Title: Multi-Dimensional Simulations of Neutrino-Driven Supernovae. Authors: Mueller, E.; Janka, H. -T. Bibcode: 1994RvMA....7..103M Altcode: No abstract at ADS Title: Hydrodynamical simulations of relativistic jets Authors: Marti, J. M.; Mueller, E.; Ibanez, J. M. Bibcode: 1994A&A...281L...9M Altcode: We have performed simulations of relativistic pressure-matched slab jets with beam Lorentz factors in the range 4.1 to 22.4 using a modern high-resolution shock-capturing technique based on an approximate relativistic Riemann solver. Our results show that the basic structural components found in Newtonian simulations, i.e. beam, cocoon, working surface and bow shock, are also present in relativistic jets. We further find that the head of the jet propagates at relativistic speed which depends on the beam velocity in a very non-linear way, and that relativistic jets seem to be more stable than Newtonian ones. Finally, our preliminary results strongly support the necessity of a more detailed study of the morphology and dynamics of relativistic jets. Title: Two- and three-dimensional simulations of convection in protoneutron stars. Authors: Müller, E. Bibcode: 1993nuas.symp...27M Altcode: The author presents some results from hydrodynamical simulations of supernova explosions, which clearly show the existence of convective instabilities in the mantle of the collapsing stellar core. Title: Simulations of the evolution of galaxy clusters. II. Dynamics of the intra-cluster gas. Authors: Schindler, S.; Muller, E. Bibcode: 1993A&A...272..137S Altcode: We present simulations of the evolution of galaxy clusters including both collisionless matter (galaxies and dark matter) and intra- cluster gas. The simulations have been performed using a direct N-body integrator for the collisionless component combined with a finite difference scheme (PPM) for the gas dynamics. With this combined method we have investigated the collision of subclusters as well as the subsequent quasi-equilibrium state by calculating several models with different initial conditions. The collision of subclusters produces several shock waves of varying strength depending on the mass of the colliding subclusters. In particular, the collision of two large subclusters causes a lens-shaped shock front. After merging the model cluster is not isothermal, but shows a hot central region (T >= 3 10^8^K) and temporarily cool regions (T <= 5 10^7^K). We have also calculated the X-ray image of the model cluster when it would be observed by ROSAT. The collision of large subclusters gives rise to distorted X-ray contours at the moment of collision and to lens-shaped contours when the strong shock front resulting from the collision begins to expand. We have also calculated X-ray temperature maps which are expected to be observable with the next generation of X-ray telescopes. We find that these temperature maps show many details of the collision, e.g., the heated gas between two subclusters shortly before their collision and the steep temperature gradients at shock fronts. Thus, the evolutionary state of a cluster can be characterized much better when these temperature data are available. An investigation of the so-called β-discrepancy shows no discrepancy in our cluster models. Our results further show that a frequent occurance of cooling flows can be one of the reasons for the β-discrepancy. Title: A comparison between SPH and PPM: simulations of stellar collisions Authors: Davies, M. B.; Ruffert, M.; Benz, W.; Muller, E. Bibcode: 1993A&A...272..430D Altcode: A full 3D implementation of the smoothed particle hydrodynamics method (SPH) is compared to the 3D Eulerian piecewise parabolic method (P PM). Both codes were used to simulate a collision between a 0.5Msun main- sequence star (modelled as a n=3/2 polytrope) and a white dwarf star of equal mass (treated as a point mass). The encounter was simulated 6 times with SPH (the number of particles ranging between 2900 and 27000) and twice with PPM (using 643 and l283 cartesian zones). A multiple grid implementation of the PPM code was also employed (5 nested grids of 323 zones each).

Our results show that the key factor determining the overall result of the collision is the form of the potential well of the point mass. Depending on the exact numerical smoothing of the well, different trajectories, amounts of mass accretion and maximum temperatures are obtained. Once both codes are run with the same point mass potential, the global values (e.g. total energy, angular momentum, center of mass trajectory, etc.) arc in good agreement. However the results differ in the values of local quantities like density distribution in the immediate vicinity of the point mass, and in the envelope structure.

The choice of an impartial test problem is difficult, since advantages and disadvantages of both methods are largely mutually exclusive. For the modeling of stellar collisions, SPH and PPM produce results that compare quite favorably. Hence, given that both schemes are fundamentally different, we assume that common features are physical in nature and not numerical. Title: Light curves of type IA supernova models with different explosion mechanisms. Authors: Khokhlov, A.; Mueller, E.; Hoeflich, P. Bibcode: 1993A&A...270..223K Altcode: The deflagration, detonation, delayed detonation, pulsating delayed detonation, and tamped detonation scenarios for Type Ia SNs are here addressed by the bolometric, blue, and visual light curves generated by a set of theoretical models. Several correlations between observable quantities and model parameters are found which allow for discrimination between models. Standard and nonstandard models are distinguished by the time-dependence of the photospheric expansion velocity, which is directly measurable by the Doppler shift of spectral lines. Title: Self-gravitating and rotating hot toroids Authors: Hashimoto, M.; Eriguchi, Y.; Arai, K.; Mueller, E. Bibcode: 1993A&A...268..131H Altcode: We solved structures of self-gravitating toroidal stars, in which the temperature is high enough for nuclear burnings to occur. For a pseudobarotropic toroidal star, we found that the maximum temperature can exceed 10 exp 9 K for some models, although there is a critical value for it within the toroid beyond which no equilibrium states exist. The maximum luminosity is found to exceed the Eddington luminosity considerably. Since the maximum temperature is the key quantity to judge which kind of nuclear burning can occur, the high temperature inside toroidal stars suggests the occurrence of significant amounts of nuclear reactions. Because essential features of toroidal stars seem to be common to accretion disks, one can also expect the possibility of appreciable nucleosynthesis inside thick accretion disks. Title: On the capabilities and limits of smoothed particle hydrodynamics Authors: Steinmetz, M.; Mueller, E. Bibcode: 1993A&A...268..391S Altcode: The capabilities and limits of smoothed particle hydrodynamics (SPH) are discussed, emphasizing the problems arising in SPH when a variable smoothing length is used and when an initial model is to be constructed. A new approach to solve the variable smoothing length problem is described which allows a more stable time integration without additional computing time. The approach is implemented into a new SPH code which uses a hierarchical binary tree method to handle self-gravity. The capabilities and limits of the SPH method are illustrated with a set of problems. Results for oscillating polytropes show that with the new approach the intrinsic numerical diffusion of the SPH method can be drastically reduced to much less than that of most multidimensional Eulerian and Lagrangian schemes. Title: Light curve models for type IA supernovae - Physical assumptions, their influence and validity Authors: Hoeflich, P.; Mueller, E.; Khokhlov, A. Bibcode: 1993A&A...268..570H Altcode: A state of the art radiation transfer code is presented for computing bolometric and monochromatic light curves of Type Ia supernovae. The radiation transfer code, which is also applicable to Type II supernovae, consists of (i) a LTE radiation transfer scheme (including an energy equation for matter and radiation, and effects due to electron and line scattering) based on the time-dependent, frequency integrated moment equations which are solved implicitly, (ii) a detailed equation of state with an elaborate treatment of the ionization balance and the ionization energies, (iii) time-dependent expansion opacities which take into account the composition structure of the explosion model, and (iv) a Monte Carlo gamma-ray deposition scheme which takes into account all relevant gamma-ray transitions and interaction processes. concerning the evolution of the structure of the explosion model a homologous expansion of the ejecta is assumed. The opacities are calculated under the assumption that temperature, density, chemical composition and expansion rate are constant over the free mean path of a photon. The mean expansion opacity which is obtained from the calculated monochromatic expansion opacities both by a Rosseland and a Planck mean, is given in tabular form. We find that the Rosseland and Planck mean opacity can differ by more than an order of magnitude. Each opacity table contains the mean expansion opacity as a function of temperature density and expansion rate for a prescribed composition. In the light curve calculations interpolations have to be performed between different tables corresponding to chemically different layers of the ejecta. Using our radiation transfer code we have calculated the bolometric and monochromatic light curves of a particular delayed detonation model (N21). The calculations have also been performed assuming various levels of physical simplifications (e.g. constant opacity diffusion approximation- no scattering) in order to study the influence and validity of many commonly made physical assumptions in modelling Type Ia supernova light curves. According to our results the temperature structure of the envelope critically depends on the use of a time- dependent opacity, the inclusion of line scattering, the correct; distinction between the frequency averaging in the radiation energy (Planck mean) and radiation flux (Rosseland mean) moment equations, and on the approximations used in the radiation transfer. In particular, the coupling between temperature profile and optical depth cannot be neglected, e.g., as done when assuming a constant opacity. Consequently, the time-dependent photospheric radius is strongly affected by the assumptions and approximations made in a light curve model. At maximum light the photospheric radius can be wrong by up to 70% with the error; increasing at later epochs. This fact can have important implications for Type Ia supernovae both for their use as distance indicators via the Baade-Wesselink method, and for their spectral analysis. Our results further show that although the bolometric light curve only depends on the total energy deposition due to the decay of ^56^Co at late epochs, its early rise, its maximum luminosity L_bol_, the time of maximum light t_bol_(max), and its early decline sensitively depend on the physical assumptions. In particular, using a time-independent opacity may cause an error in L_bol_(max) of about 50% and in t_bol_(max) of about 3.5 days, respectively. In order to obtain accurate monochromatic light curves line scattering effects must be taken into account, because otherwise most of the flux will erroneously be emitted in the infrared. Title: Galaxy formation in a cluster environment: first steps to a consistent description. Authors: Steinmetz, M.; Müller, E. Bibcode: 1993AGAb....8...16S Altcode: 1993AGAb....8...16. No abstract at ADS Title: Gamma-ray light curves and spectra for SN IA Authors: Hoeflich, P.; Mueller, E.; Khokhlov, A. Bibcode: 1993A&AS...97..221H Altcode: Based on detailed Monte Carlo calculations, we present gamma-ray energy deposition functions, gamma-ray light curves and gamma-ray spectra for a large set of theoretical models of Type Ia supernovae. They include 'classical' detonation and deflagration models, recently proposed delayed detonation models, and tamped detonation models, which may crudely resemble merger or common envelope configurations. Title: Nucleosynthesis in type Ia supernovae: effects of non-spherical detonations Authors: Steinmetz, M.; Müller, E. Bibcode: 1993nuco.conf..563S Altcode: No abstract at ADS Title: Gravitational radiation from the collapse of rotating stellar cores. Authors: Schäfer, G.; Mönchmeyer, R.; Müller, E. Bibcode: 1993rges.conf..278S Altcode: 1993rges.rept..278S The authors present gravitational waveforms derived from data of four numerical model calculations of axisymmetric collapse processes in rotating 1.36 Msun stellar iron cores. The maximal amplitudes (at a distance of 10 Mpc) range from 4×10-24 to 2×10-23, the frequencies at maximum spectral energy density have values of 100 Hz - 700 Hz and the radiated energy is in the range (0.2 - 8.0)×10-8Msunc2. In comparison to previous calculations the obtained waveforms show standard and non-standard features. Title: Neutrino-driven type-II supernovae: neutrino heating and post bounce dynamics. Authors: Janka, H. -T.; Müller, E. Bibcode: 1993fna..conf..203J Altcode: The currently most promising model to explain the explosion of massive stars (8 Msun ⪉ M ⪉ 25 Msun) in type-II supernovae is the "delayed mechanism" by neutrino heating. A small fraction of the order of one per cent of the total energy carried away from the collapsed stellar core in form of neutrinos, several 1053erg, is thought to be transferred to the material outside and close to the newly formed protoneutron star. This energy causes a huge expansion, by which an extended region of low density, but quite high temperature, is created above the surface of the young neutron star. The persistent energy input by neutrinos maintains high pressure in this region, thus driving the supernova shock into the stellar mantle and reversing the star's infall to an explosion. In this work the dynamics of such a scenario are investigated by numerical simulations of the formation and evolution of the hot bubble region around the newly born neutron star in one dimension. The equation of state of the stellar gas as well as the interactions between neutrinos and the gas particles are described with a high degree of accuracy. These simulations show that the explosion energy stays too low, i.e. of the order of a few 1050erg instead of the expected 1 - 1.5×1051erg for a typical type-II supernova explosion, unless one "adds" a mechanism of efficient neutrino heating during the early phase (⪉1 second) of the post-bounce evolution. This strongly indicates the lack of important physics in spherically symmetric simulations. The authors show first results of hydrodynamical simulations in two dimensions to study possible effects of convection inside the newly formed neutron star and between the compact remnant and the outward moving supernova shock. Title: A comparison of calculated and observed monochromatic type IA supernova light curves Authors: Mueller, E.; Hoeflich, P. Bibcode: 1992STIN...9417629M Altcode: The calculated monochromatic light curves of a set of type Ia supernova models are compared with the observed monochromatic light curves of 13 type Ia Supernovae (SNIa). The set consists of 11 type Ia supernova models including deflagrations, detonations, delayed detonations, pulsating delayed detonations and tamped detonations. The theoretical light curves were calculated using our recently developed light curve model. The model incorporates a detailed equation of state with an elaborate treatment of the ionization balance, an implicit grey LTE (Local Thermodynamic Equilibrium) radiation transport scheme based on the moment equations, a total energy equation for the gas and the radiation field, expansion opacities, and a Monte Carlo gamma ray deposition scheme. To evolve the structure of the underlying explosion models homologous expansion is assumed. Based on a comparison of theoretical light curves and observational data, the distances of the patent galaxies were determined. It is shown that SNe Ia allow for a measurement of the value of the Hubble constant provided individual fits are used and if they are located at distances larger than 15 Mpc, because only then they are in the 'Hubble' flow. Taking this restriction into account a Hubble constant can be derived within a 2 sigma error. Title: Gamma-ray light curves and spectra for Type IA supernovae Authors: Hoeflich, P.; Khokhlov, A.; Mueller, E. Bibcode: 1992A&A...259..549H Altcode: The gamma-ray energy deposition functions, light curves, and spectra have been computed for a set of theoretical Type Ia supernova models including deflagration, detonation, delayed detonation, and tamped detonation models. The results have been obtained with a Monte Carlo gamma-ray deposition scheme that takes all relevant gamma transitions and interaction processes into account. The computations demonstrate that Type Ia supernova models can be discriminated and that the absolute amount of Ni-56 synthesized in the event can be determined from the gamma-ray light curves and spectra. Title: Carbon Detonations in Rapidly Rotating White Dwarfs Authors: Steinmetz, M.; Muller, E.; Hillebrandt, W. Bibcode: 1992A&A...254..177S Altcode: We have performed a set of two-dimensional hydrodynamic simulations of the propagation of detonation waves in rapidly rotating white dwarfs. The axisymmetric initial models used in the simulations are in rotational equilibrium and possess a density stratification similar to that of configurations predicted by the merging scenario of Type Ia supernovae. The energy release is approximated by a single exothermic nuclear reaction 14 12C → 3 56Ni proceeding at the rate of the 12C(12C,4He)20Ne reaction. Central and off-center ignitions have been studied.

When burning is ignited in the center our results show, that independently of the shape of the star, all matter is burned into iron group elements and the star is completely disrupted after typically 200 msec. Igniting the white dwarf in an extended central region having a more or less flattened spheroidal or cylindrical shape gives rise to an initially different behaviour, but within about 100 msec the shape of the detonation wave approaches that of one being ignited only in the center. When burning is ignited off-center all carbon is consumed, too. Thus detonations in non-spherical massive white dwarfs cannot explain the observed intermediate mass elements seen in the spectra of Type Ia supernovae. Title: Gravitational waves from supernova explosions. Authors: Müller, E.; Mönchmeyer, R.; Schäfer, G. Bibcode: 1992AGAb....7...57M Altcode: No abstract at ADS Title: Hydrodynamical cosmology: galaxy formation in a cosmological context. Authors: Steinmetz, M.; Müller, E. Bibcode: 1992AGAb....7...15S Altcode: No abstract at ADS Title: Type IA supernovae : theoretical light curves with a slow pre-maximum rise. Authors: Khokhlov, A.; Mueller, E.; Hoeflich, P. Bibcode: 1992A&A...253L...9K Altcode: We present theoretical light curve (LC) calculations which reproduce Type Ia supernovae with a slow pre-maximum rise (V maximum at ~ 20 days), like the recently observed SN 1990 N. We use the same input physics as in our previous work (Hoflich et al. 1991). In addition, both Thomson and line scattering has been included, which is crucial for reproducing the monochromatic LC. For the radiation transport the moment equations are solved. Our calculations are based on delayed detonation models in which the transition from a deflagration to a detonation occurs due to the pulsation of an exploding white dwarf. The interaction with an extended low density envelope created during the pulsation leads to a substantial redistribution of the kinetic energy inside the ejecta. The deceleration of the bulk of matter to <~ 10000 km/sec delays the rise time of the light curve from ~ 10 - 12 days, typical of delayed detonation models without a pulsation, to ~ 17 days, whereas the outer envelope acquires velocities of up to 30000 km/sec. The interaction with the extended ~10^10^ cm envelope is not specific to the delayed detonation scenario. To illustrate the effect we present the results of computations of the explosion of 1.2 M_sun_CO-WD inside an extended envelope of 0.8 M_sun_, which results in a rise time of ~ 25 days. Title: Instability and clumping in SN 1987A. Authors: Mueller, E.; Fryxell, B.; Arnett, D. Bibcode: 1991A&A...251..505M Altcode: Two-dimensional hydrodynamic calculations of Rayleigh-Taylor instabilities in the ejecta of SN1987A are described. These calculations covering the first few hours of the evolution were performed on a grid of 1000^2^, which provides significantly better resolution than obtained in previous calculations (Fryxell et al. 1991). As a result of the improved resolution, two new regions of instability were discovered. In addition, the structure of the Rayleigh-Taylor fingers became much more complex. The numerical experiment was found to be consistent with a linear stability analysis. In addition, we compare the two-dimensional results to the results of a one-dimensional calculation to show the effects of the nonspherical motion on the structure and composition distribution of the ejecta. Title: Multi-Dimensional Calculations of Instabilities in Supernova Explosions Authors: Fryxell, B. A.; Müller, E.; Arnett, D.; Ruffert, M. Bibcode: 1991BAAS...23.1407F Altcode: No abstract at ADS Title: Type IA supernovae : gamma-rays as predicted by delayed detonation modelsand SN 1991T. Authors: Mueller, E.; Hoeflich, P.; Khokhlov, A. Bibcode: 1991A&A...249L...1M Altcode: We have computed the γ-ray spectra for two delayed detonation models of Khokhlov (1991a, b). The results have been obtained with a Monte Carlo γ-ray deposition scheme being part of our detailed supernova light curve model. For a source located at a distance of 10 Mpc the delayed detonation model, which best fits observed light curves of "fast" type Ia supernovae and is capable to reproduce their spectra, predicts a γ-ray flux for the ^56^Co line at 847 keV easily detectable by COMPTEL. Our computations also strongly indicate that SN Ia models can be discriminated on the basis of early time γ-ray observations. Concerning the recently discovered type Ia supernova SN 1991T the delayed detonation model predicts a γ-ray flux for the 847 keV line of 1.0 10^-3^ photons s^-1^ cm^-2^ MeV^-1^ for day 81 (i.e., June 23, 1991 for SN 1991T), and of 3.8 10^-4^ photons s^-1^ cm^-2^ MeV^-1^ for day 190 (i.e., October 10, 1991 for SN 1991T). The theoretical spectra have been folded with the energy response function which gives rise to a significant modification of the original spectra. The number of photons predicted for the 847 keV line for an integration time of 5 10^5^ s are about 310 at day 81 and 150 at day 190, respectively. Title: Structure of rapidly rotating axisymmetric stars. I - A numerical method for stellar structure and meridional circulation Authors: Eriguchi, Y.; Mueller, E. Bibcode: 1991A&A...248..435E Altcode: A numerical method is presented for calculating the mechanical and thermal structure of stationary axisymmetric inviscid rotating stars in which the velocity of the meridional flow is very slow. The structure of the rotating configuration is computed and the flow pattern for the given configuration is calculated. Several sequences of stationary configurations for three different rotation laws are computed. For the energy generation, the point source model is assumed and two kinds of opacities (electron scattering opacity and Kramers opacity) are examined. A two-zone flow pattern is found in the uniformly rotating models. Models with two kinds of differential rotation laws are investigated. The flow patterns in these differentially rotating models are found to be quite different from those of the uniformly rotating models. Specifically, near the rotation axis, the flow rising from the convective core directly reaches the surface of the star. Title: Type IA supernovae : theoretical light curves for SN 1972E and SN 1981B. Authors: Hoeflich, P.; Mueller, E.; Khokhlov, A. Bibcode: 1991A&A...248L...7H Altcode: Based on delayed detonation models of Khokhlov (1991a,b) theoretical light curves have been calculated, which accurately reproduce the observed light curves of the Type Ia supernovae SN 1972E and SN 1981B. Our models describe very well both the pre-maximum rise and the post-maximum decline of the light curve and also give the correct maximum luminosity. The theoretical light curves are calculated using (i) a detailed equation of state with an elaborate treatment of the ionization balance, (ii) an implicit LTE radiation transport scheme based on a modified diffusion approximation with space and time dependent correction factors determined by the exact solution of the radiation transport equation at low optical depths (τ <~ 100), (iii) tabulated time- dependent expansion opacities which take into account the composition structure of the initial model,(iv) a Monte Carlo γ-ray deposition scheme, and (v) homologous expansion to evolve the structure of the models. Title: New orbits for WDS 02231+7021, WDS 05373+6642, WDS 06425+6612 WDS 22356+5413. Authors: Muller Bibcode: 1991IAUDS.114....1M Altcode: No abstract at ADS Title: Gravitational waves from the collapse of rotating stellar cores. Authors: Moenchmeyer, R.; Schaefer, G.; Mueller, E.; Kates, R. E. Bibcode: 1991A&A...246..417M Altcode: The paper presents calculations of the gravitational quadrupole, octupole, and hexadecapole waves resulting from four different numerical axisymmetric iron core collapse models for rotating 1.36 solar-mass iron cores of 20 solar-mass stars. A recently derived analytic expression was used to determine the waveforms. The four resulting waveforms obtained show qualitatively and quantitatively different shapes, characteristic of the abundance mechanisms of the models. The dimensionless amplitudes range up to 2 x 10 to the -23 at a distance of 10 Mpc with the maximum of the power spectrum in the frequency range 500-1000 Hz. For the most efficient model, the radiated energy is calculated to be equal to 8 x 10 to the -8th solar mass times c-squared. Title: Nuclear astrophysics. Proceedings. Authors: Hillebrandt, W.; Müller, E. Bibcode: 1991nap..book.....H Altcode: Contents: 1. Nuclear properties and reactions of relevance to astrophysics. 2. s-process nucleosynthesis studies. 3. Stellar evolution, nucleosynthesis, and abundances in stars. 4. Supernovae and supernova nucleosynthesis. 5. Chemical evolution of globular clusters and galaxies. Title: High Resolution Numerical Simulations of Instabilities, Mixing, and Clumping in Supernova 1987A Authors: Müller, E.; Fryxell, B.; Arnett, D. Bibcode: 1991ESOC...37...99M Altcode: 1991sos..conf...99M No abstract at ADS Title: Influence of Time Dependent Opacities on Light Curves of Type II Supernovae Authors: Müller, E.; Höflich, P. Bibcode: 1991ESOC...37..379M Altcode: 1991sos..conf..379M No abstract at ADS Title: Supernovae that are not Spheres Authors: Arnett, D.; Fryxell, B.; Müller, E. Bibcode: 1991ESOC...37..117A Altcode: 1991sos..conf..117A No abstract at ADS Title: Instabilities and Mixing in Supernova 1987A Authors: Arnett, D.; Fryxell, B.; Muller, E. Bibcode: 1991supe.conf..232A Altcode: No abstract at ADS Title: TOPICAL REVIEW: Supernova theory and the nuclear equation of state Authors: Muller, E. Bibcode: 1990JPhG...16.1571M Altcode: No abstract at ADS Title: Three-dimensional hydrodynamical simulations of off-centre collisions between a white dwarf and a main-sequence star Authors: Ruffert, M.; Mueller, E. Bibcode: 1990A&A...238..116R Altcode: A finite difference code based on the piecewise parabolic method is used here to study off-center collisions between an 0.5 solar mass main-sequence star (MSS) modeled by a polytrope index of 1.5 and an 0.5 solar mass white dwarf (WD) modeled by a point-mass potential. At small impact parameters, the MSS is totally disrupted, its matter eventually settling around the WD, while for large impact parameters the MSS is only slightly elongated. The amount of mass becoming unbound due to the collision is estimated to be roughly 15 percent. The expansion of the shock-heated gas is spherically symmetric. The maximum temperatures reached during the collision are so low that the nuclear energy production is negligible. Title: Thermal instabilities in cooling flows - The evolution of nearly spherical perturbations Authors: Brinkmann, W.; Mueller, E.; Massaglia, S. Bibcode: 1990A&A...237..536B Altcode: Numerically, in one and two dimensions, the temporal evolution of thermally unstable blobs is presently followed in connection with the problem of mass accretion in cooling flows. The hydrodynamic equations are solved in spherical geometry for an initially homogeneous cooling medium, including thermal conduction. The initial isobaric perturbations are followed in time until self gravity effects, not included in the equations, are thought to become important. In the one-dimensional case, after the linear phase the perturbation evolves on time scales much shorter than the linear ones, and depending on the initial matter density, a cool, dense core of size about 0.001-0.01 times the initial perturbation scale size forms. This grows in size due to continuous accretion from the (hotter) outside gas and may become eventually gravitationally unstable. Title: Numerical simulations of axially symmetric magnetized jets. I - The influence of equipartition magnetic fields. II - Apparent field structure and theoretical radio maps. III - Collimation of underexpanded jets by magnetic fields Authors: Koessl, D.; Mueller, E.; Hillebrandt, W. Bibcode: 1990A&A...229..378K Altcode: The results of a numerical MHD model are discussed, which we have used to investigate the influence of equipartition magnetic fields on the propagation of supersonic jets. We find that a purely poloidal equipartition field is capable of decollimating the jet, whereas a purely toroidal equipartition field increases the confinement, but introduces pinching waves. These oscillations can be stabilized by an additional poloidal field without destroying the collimation. Title: Numerical Simulations of Axially Symmetric Magnetized Jets - Part Three - Collimation of Underexpanded Jets by Magnetic Fields Authors: Kossl, D.; Muller, E.; Hillebrandt, W. Bibcode: 1990A&A...229..401K Altcode: Using a finite difference scheme based on the FCT-algorithm, we have performed a set of hydrodynamic and magnetohydrodynamic simulations to investigate the stability of both magnetized and unmagnetized underexpanded (ζ_H_ = 10) jets. We find that unmagnetized jets with a fairly high Mach number (Ma_B_ = 6) are stable; low Mach number jets (Ma_B_ <~ 2), on the other hand, exhibit prominent instabilities. A toroidal magnetic fie1d of approximately equipartition field strength is capable of stabilizing these instabilities due to the pinch effect. However, it changes the morphology of the jet completely by generating a nose cone. The influence of an additional poloidal magnetic field, with a field strength comparable to the fie1d strength of the toroidal component, is small. Its main effect is that it forces part of the nose cone into a sonic rotation. Title: Numerical Simulations of Axially Symmetric Magnetized Jets - Part Two - Apparent Field Structure and Theoretical Radio Maps Authors: Kossl, D.; Muller, E.; Hillebrandt, W. Bibcode: 1990A&A...229..397K Altcode: The results of numerical MHD models are used to compute apparent field configurations and theoretical radio maps of extragalactic jets. We find that the apparent field structure of weak (FR I) radio sources is readily explained by the projection of the true field configuration onto a plane perpendicular to the line of sight. Furtheron it is demonstrated that it is unlikely that the X-like shock structures, which are found in almost any numerical simulation of supersonic jets, produce the prominent knots observed in the jets of edge-darkened extragalactic radio sources. Title: Thermal instabilities in cooling flows: The evolution of nearly spherical perturbations Authors: Brinkmann, W.; Massaglia, S.; Mueller, E. Bibcode: 1990STIN...9119365B Altcode: The temporal evolution of thermally unstable blobs in connection with the problem of mass accretion in cooling flows is studied numerically, in one and two dimensions. The hydrodynamic equations are solved in spherical geometry for an initially homogeneous cooling medium, including thermal conduction. The initial isobaric perturbations are followed in time until self gravity effects, not included in the equations, are thought to become important. In the one dimensional case, it is found that after the linear phase the perturbation evolves on time scales much shorter than the linear ones and depending on the initial matter density, a cool, dense core of size approximately 0.001 - 0.01 times the initial perturbation scale size forms. This grows in size due to continuous accretion from the (hotter) outside gas and may become eventually gravitationally unstable. The one dimensional results are compared with others obtained for a plane-parallel slab geometry. The qualitative difference between a one dimensional and a two dimensional calculation with otherwise very similar physical parameters is shown. Title: Carbon detonation in differentially rotating, highly deformed white dwarfs. Authors: Steinmetz, M.; Hillebrandt, W.; Müller, E. Bibcode: 1990AGAb....5...14S Altcode: No abstract at ADS Title: Computations of multi-dimensional flows with non-uniform composition Authors: Fryxell, B.; Müller, E.; Arnett, D. Bibcode: 1990nuas.symp..100F Altcode: No abstract at ADS Title: Mixing due to Rayleigh-Taylor instabilities in SN 1987A Authors: Müller, E.; Hillebrandt, W.; Orio, M.; Höflich, P.; Mönchmeyer, R.; Arnett, D.; Fryxell, B. Bibcode: 1990nuas.symp..103M Altcode: No abstract at ADS Title: Instabilities and Mixing in Supernova 1987A Authors: Fryxell, B. A.; Arnett, W. D.; Müller, E. Bibcode: 1989BAAS...21.1209F Altcode: No abstract at ADS Title: Mixing and fragmentation in supernova envelopes. Authors: Muller, E.; Hillebrandt, W.; Orio, M.; Hoflich, P.; Monchmeyer, R.; Fryxell, B. A. Bibcode: 1989A&A...220..167M Altcode: The possibility that a Rayleigh-Taylor instability may lead to an early fragmentation of a supernova shell is investigated by means of 1-, 2-, and 3-dimensional hydrodynamic simulations. In particular, a 'point ' explosion in a n = 3 polytrope is considered, but, in contrast to recent simulations with smoothed particle hydrodynamics, no evidence was found for fragmentation of the shell. These results are in accord with analytic considerations. Title: A Conservative Second-Order Difference Scheme for Curvilinear Coordinates - Part One - Assignment of Variables on a Staggered Grid Authors: Monchmeyer, R.; Muller, E. Bibcode: 1989A&A...217..351M Altcode: A conservative second-order difference scheme for solving the equations of ideal hydrodynamics is described. Although it is capable of dealing with general orthogonal curvilinear coordinates, it was mainly developed for calculating the axisymmetric collapse of rotating stellar cores in spherical coordinates.

The basic features of the scheme are: (i) variables are assigned to "volume centers" of the computational cells and not to "geometrical cell centers" as usual; (ii) the spatial discretization is of second-order accuracy and includes monotonicity constraints; (iii) advectional changes are calculated by using a "volume advection scheme" instead of evaluating interface integrals of the advection fluxes; (iv) the time evolution is described by an explicit, second-order accurate discretization (v) a moving non-equidistant, staggered grid can be used. In addition a Poisson solver for axially symmetric mass distributions is incorporated into the scheme.

In this paper it is demonstrated that for the simple but important test problem of a spherical dust collapse the proposed difference scheme avoids the pitfalls occurring whenever a discretization scheme originally developed for straight coordinates is applied to curvilinear Eulerian coordinates in a straightforward way. Title: Hydrodynamics of the interstellar gas in colliding galaxies. II. Non-central collisions. Authors: Mueller, E.; Mair, G.; Hillebrandt, W. Bibcode: 1989A&A...216...19M Altcode: The dynamical and thermal evolution of the warm component of the interstellar medium during a fast non-central collision of two galaxies is investigated by means of 3-dimensional hydrodynamic simulations using a non-equidistant Cartesian grid of up to 10^6^ grid points. The dynamics of the stellar component of the galaxies is not followed in detail, but its influence on the gas is incorporated into the model through its gravitational potential, which is assumed to be of fixed shape. The collision of the galaxies is simulated by a constant relative motion of the two potential wells, which contain the isothermal interstellar gas in hydrostatic equilibrium. Radiative losses of the gas are calculated with the aid of cooling function, and the self-gravity of the gas component is neglected. We have performed four simulations varying the relative velocity, the impact parameter and the number of grid points, respectively. We find that the amount of matter leaving the galaxies in form of hot gas in case of a large relative velocity (2 10^3^ km s^-1^) is roughly proportional to the cross-sectional volume of the two galaxies, which is equal to the total volume in case of a head-on collision. Comparing the results of two collisions where the impact parameter was the same but the relative velocity differed by a factor of two we find that the gas forms a cool dense ρ > 10^24^ g cm^-3^) disk-like, probably gravitationally bound object torn apart between the withdrawing galaxies. Title: Proceedings of the 5th Workshop on Nuclear Astrophysics. Authors: Hillebrandt, W.; Müller, E. Bibcode: 1989nuas.proc.....H Altcode: No abstract at ADS Title: Computation of multi-dimensional flows with non-uniform composition. Authors: Fryxell, B.; Müller, E.; Arnett, D. Bibcode: 1989nuas.conf..100F Altcode: Many astrophysical objects display complex multi-dimensional behavior. In order to fully understand many of these objects, it is necessary to compute flows of gas which are made up of an arbitrary mixture of nuclear species. There are at least two types of situations where following abundance changes is crucial. One is in the propagation of detonation and deflagration fronts such as those occurring in supernovae, novae, X-ray bursts, gamma-ray bursts, and shell flashes in stars. Here, the nuclear energy released by the propagation of the burning front is directly related to the composition of the material ahead of the front. A second important class of calculations involves determing the amount of mixing of nuclear species which occurs in stars. This paper describes the development of a numerical code for studying these processes. Title: Mixing due to Rayleigh-Taylor instabilities in SN 1987A. Authors: Müller, E.; Hillebrandt, W.; Orio, M.; Höflich, P.; Mönchmeyer, R.; Arnett, D.; Fryxell, B. Bibcode: 1989nuas.conf..103M Altcode: The early discovery of soft and hard X-rays as well as of γ-ray line emission from supernova 1987A indicates that radioactive 56Co has been mixed from the deep interior of the exploding star into the hydrogen-rich envelope. This paper reports numerical simulations of the mixing process by modeling the supernova explosion using a 3-d explicit Eulerian hydrodynamic code. Title: Models of head-on collisions between a white dwarf and a low-mass main sequence star Authors: Rozyczka, M.; Yorke, H. W.; Bodenheimer, P.; Mueller, E.; Hashimoto, M. Bibcode: 1989A&A...208...69R Altcode: Two-dimensional axisymmetric hydrodynamical calculations are performed to simulate the collision of a white dwarf of 0.5 solar mass with main sequence stars of 0.5 and 1.0 solar masses. A substantial amount of the main sequence star is dissipated in the collision; however the amount is dependent on its mass and on the initial velocity of the white dwarf. Although nuclear reactions were not included in the hydrodynamic calculations, detailed estimates of reaction rates, based upon the numerical results, indicate that shock heating is the dominant mechanism causing dissipation. The precise role of nuclear energy is not determined because of uncertainties arising from the approximations and the finite grid. In all calculated cases the amount of material captured by the white dwarf is sufficient so that it subsequently will evolve into a red giant. Title: Core collapse with rotation and neutron star formation Authors: Mönchmeyer, R.; Müller, E. Bibcode: 1989ASIC..262..549M Altcode: Numerical simulations of the collapse of non-rotating and rotating cores of massive stars (M ≥ 8 Msun) are presented. After reviewing briefly the underlying physics the numerical results are discussed and possible consequences for neutron star formation are outlined. Title: Book Review: Nuclear astrophysics. / Springer, 1987 Authors: Kuhfuss, R.; Muller, E.; Truran, J. W.; Doom, C. Bibcode: 1989SSRv...51R.425H Altcode: No abstract at ADS Title: Constraints on the Nuclear Equation of State from Type II Supernovae and Newly Born Neutron Stars Authors: Hillebrandt, W.; Müller, E.; Monchmeyer, R. Bibcode: 1989ASIB..216..689H Altcode: 1989nesa.confA.689H No abstract at ADS Title: Numerical simulations of astrophysical jets: the influence of boundary conditions and grid resolution. Authors: Koessl, D.; Mueller, E. Bibcode: 1988A&A...206..204K Altcode: A new type of flux-corrected-transport (FCT) algorithm is described. Test calculations show that the new algorithm is superior to earlier FCT-versions. The algorithm is used to investigate the influence of boundary conditions and grid resolution on the simulation of supersonic jet propagation. We find that the solution is sensitive to the upwind boundary condition even in late stages of the jet evolution. Furthermore it is demonstrated that a converged solution cannot be obtained with the grid resolution which has been assumed to be sufficient in other simulations. Limitations arising in any jet simulation when trying to compare the numerical results with observations are pointed out. Title: Density functional calculations in strong magnetic fields - The ground state properties of atoms Authors: Koessl, D.; Wolff, R. G.; Mueller, E.; Hillebrandt, W. Bibcode: 1988A&A...205..347K Altcode: The ground state binding energy, the ionisation energy, the electron density distribution and the quadrupole moment of iron atoms in strong magnetic fields (1 - 8×1012G) have been calculated using the density functional method. The authors have also performed calculations of the ground state energy for helium, carbon, and oxygen atoms, and for the helium-like ions of carbon (C4+), oxygen (O6+) and iron (Fe24+), respectively. Finally, they have calculated the binding energy (per atom) of a hexagonal iron crystal due to the quadrupole-quadrupole interaction of the deformed iron atoms. Title: Book Review: Nuclear astrophysics. / Springer, 1987 Authors: Kuhfuss, R.; Muller, E.; Truran, J. W.; Tayler, R. J. Bibcode: 1988Obs...108..187H Altcode: No abstract at ADS Title: Hydrodynamics of the interstellar gas in colliding galaxies Authors: Mair, G.; Mueller, E.; Hillebrandt, W.; Arnold, C. N. Bibcode: 1988A&A...199..114M Altcode: The dynamical and thermal evolution of the warm component of the interstellar medium during a fast head-on collision of two galaxies is investigated by means of two-dimensional hydrodynamic simulations. The dynamics of the stellar component of the galaxies is not followed in detail, but its influence on the gas is incorporated into the model through its gravitational potential which is assumed to be of fixed shape. The collision of the galaxies is simulated by a constant relative motion of the two potential wells, which contain the isothermal interstellar gas in the hydrostatic equilibrium. Radiative losses of the gas are calculated with the aid of a cooling function, and the self-gravity of the gas component is neglected. In the given parameter space of relative velocity, escape velocity and chemical composition of the interstellar matter the total gas content of the colliding galaxies is swept out. In the case of a large relative velocity (2 10^3^ km s^-1^) the matter is leaving the galaxies in form of hot gas, while for a smaller relative velocity (10^3^ km s^-1^) the gas forms a cool disk-like, probably gravitationally bound object between the withdrawing galaxies. Title: Book-Review - Nuclear Astrophysics - LECTURE-NOTES/PHYSICS:287 Authors: Hillebrandt, W.; Kuhfuss, R.; Muller, E.; Truran, J. Bibcode: 1988JBAA...98..140H Altcode: No abstract at ADS Title: Book-Review - Nuclear Astrophysics Authors: Hillebrandt, W.; Kuhfuss, R.; Muller, E.; Truran, J. W. Bibcode: 1988S&T....75Q.161H Altcode: No abstract at ADS Title: Report of IAU Commission 38: Exchange of astronomers (Echange des astronomes). Authors: Müller, E. A. Bibcode: 1988IAUTA..20..537M Altcode: No abstract at ADS Title: Reminiscences: Zürich, 1948: first post-WWII General Assembly. Authors: Müller, E. A. Bibcode: 1988itod....4....4M Altcode: No abstract at ADS Title: Size Dependence of Surface Thermodynamic Parameters of Microclusters and the Location of the Gibbs' " Surface of Tension" Authors: Müller, E.; Vogelsberger, W.; Fritsche, H. -G. Bibcode: 1988LNP...309..442M Altcode: 1988aan..conf..442M No abstract at ADS Title: Indications for black hole formation from neutrino observations in SN1987a. Authors: Hillebrandt, W.; Hoflich, P.; Kafka, P.; Muller, E.; Schmidt, H. U.; Truran, J. W. Bibcode: 1987A&A...180L..20H Altcode: Neutrinos detected by both the KAMIOKA and IMB experiments, five hours after the neutrino pulse seen in the Mont Blanc experiment, indicate that the neutron star formed in the supernova SN 1987A in the LMC may have collapsed further to a black hole. Since this should have happened within less than a second, the KAMIOKA-data suggest the arrival of two distinct groups of neutrinos with different rest masses. The six events arriving during the first second can be fitted by a rest mass of 7.6(+4, -3) eV/c2, which would be still consistent with the previous estimate from the Mont Blanc data (Hillebrandt et al. 1987A). The second group requires a larger rest mass of 69(+24, -45) eV/c2. Title: Evidence for a finite electron neutrino rest mass from SN 1987A. Authors: Hillebrandt, W.; Hoflich, P.; Kafka, P.; Muller, E.; Schmidt, H. U.; Truran, J. W.; Wampler, J. Bibcode: 1987A&A...177L..41H Altcode: The detected neutrino pulse of finite width correlated with the optical discovery of SN 1987A in the LMC allows the determination of the neutrino rest mass. Taking into account possible uncertainties in both the original width of the emitted neutrino pulse and the expected neutrino energy spectrum from type II supernovae, an electron neutrino rest mass of 11-23 eV/c sq is derived, in agreement with the recent limit obtained from decay experiments. Title: Evidence for black hole formation from neutrino observations in SN 1987a. Authors: Hillebrandt, W.; Höflich, P.; Kafka, P.; Müller, E.; Schmidt, H. U.; Truran, J. W. Bibcode: 1987MPARp.278....5H Altcode: No abstract at ADS Title: Computational problems in supernova simulations. Authors: Müller, E. Bibcode: 1987CoPhC..44..271M Altcode: Theoretical models of type I and type II supernova explosions are reviewed from a computational physics point of view. After discussing briefly the underlying physics the numerical problems and challenges encountered in the simulation of type I and type II supernova are addressed. Title: Hydrodynamics of the interstellar gas in colliding galaxies. I. Head-on collisions. Authors: Mair, G.; Müller, E.; Hillebrandt, W.; Arnold, C. N. Bibcode: 1987MPARp.314.....M Altcode: No abstract at ADS Title: Evidence for a finite electron neutrino rest mass from SN 1987a. Authors: Hillebrandt, W.; Höflich, P.; Kafka, P.; Müller, E.; Schmidt, H. U.; Truran, J. W.; Wampler, J. Bibcode: 1987MPARp.278....1H Altcode: No abstract at ADS Title: Meridional flow in a self-gravitating body. I. Mechanical flow in a barotropic star with constant specific angular momentum. Authors: Eriguchi, Y.; Mueller, E.; Hachisu, I. Bibcode: 1986A&A...168..130E Altcode: The mechanical part of the equations governing meridional circulation in a self-graviting body is solved. Stationary axisymmetric solutions are computed neglecting the effects of viscosity and assuming that the fluid is incompressible and has a constant specific angular momentum. Then, the vorticity has a simple relation to the stream function. Three types of models are investigated: (1) nonrotating configurations of spherical topology which are deformed due to the internal motion (pure circulation case); (2) rotating configurations of toroidal topology; and (3) models consisting of a rotating toroidal configuration and a central point mass (accretion disk case). Assuming appropriate choices of the vorticity stream function relation, several stationary sequences are computed. The models obtained contain one or several large scale circulations in the meridional plane. The configuration change due to circulation is small, i.e., the shape is mainly determined by three forces, the pressure gradient, the gravity, and the centrifugal force. Title: Carbon Combustion Supernovae: Numerical Studies of the Final Evolution of Degenerate Carbon-Oxygen Cores Authors: Mueller, E.; Arnett, W. D. Bibcode: 1986ApJ...307..619M Altcode: The authors have performed and analyzed a set of numerical experiments of the core carbon flash, which treat axisymmetric hydrodynamic flow directly rather than use a phenomenological theory of convection. The numerical experiments show a variety of possible evolutionary paths for degenerate carbon-oxygen cores, ranging from spherical detonations to nonspherical deflagrations. The results show that the initially spherically symmetric burning front is Rayleigh-Taylor unstable. In all experiments except the one leading to a detonation, some carbon is not burned to nickel. Furthermore, all experiments lead to a total disruption of the core, leaving no condensed remnant. Title: Nuclear-reaction networks and stellar evolution codes - The coupling of composition changes and energy release in explosive nuclear burning Authors: Mueller, E. Bibcode: 1986A&A...162..103M Altcode: A robust method is presented for calculating abundance changes and entropy (or energy) generation with a nuclear-reaction network within a stellar evolution code in case of explosive nuclear burning. The robustness of the method is due to the fact that the rate equations and the entropy (or energy) equation are solved together by the Newton-Raphson technique. This guarantees that the strong temperature dependence of the nuclear-reaction rates does not lead to instabilities. The main advantage of the method is its capability to calculate nuclear transmutations while entering or leaving the regime of nuclear statistical equilibrium. This capability of the method is demonstrated for an extreme test case. In addition an efficient implementation of the method on vector processors is discussed. Title: Nuclear-reaction networks and stellar evolution codes: on the coupling of composition changes and energy release in explosive nuclear burning. Authors: Müller, E. Bibcode: 1986ana..work..259M Altcode: No abstract at ADS Title: Nuclear-reaction networks and stellar evolution codes: on the coupling of composition changes and energy release in explosive nuclear burning. Authors: Müller, E. Bibcode: 1986MPARp.220.....M Altcode: No abstract at ADS Title: Differentially Rotating Equilibrium Models - Collapse of Rotating Degenerate Configurations Authors: Muller, E.; Eriguchi, Y. Bibcode: 1986ASIC..163..143M Altcode: 1986ninp.proc..143M No abstract at ADS Title: Equilibrium models of differentially rotating, completely catalyzed, zero-temperature configurations with central densities intermediate to white dwarf and neutron star densities Authors: Mueller, E.; Eriguchi, Y. Bibcode: 1985A&A...152..325M Altcode: We have calculated axisymmetric equilibria of differentially rotating, completely catalyzed, zero-temperature Newtonian configurations with central densities in the range 10 7 gcm-3 <= Qc < 5 1014 gcm -3. Our aim was to address the following question: is it possible for rotating white dwarfs with a mass larger than the Chandrasekhar mass to evolve, via angular momentum losses, to a neutron star on a secular time scale, i.e. without a sudden release of gravitational energy in the form of an optical supernova outburst? Our results show that dynamically stable (against collapse) rotating equilibrium models exist up to densities of ≍ 1011 gcm-3 (without rotation ≍ 10 9 gcm-3) and with masses up to 1.7 Msun (without rotation 1.0 Msun). Configurations with masses in the range 1.7 < M/Msun < 2.2 are also dynamically stable, but secularly unstable against non-axisymmetric perturbations. We find that for all studied combinations of mass, angular momentum and angular momentum distribution the evolution of a rotating (cold) white dwarf must become dynamic at densities around 1012 gcm-3, i.e. roughly 80 % of the neutron star's binding energy will be released on a dynamical time scale. Title: Supernova-induced collapse of magnetic interstellar clouds Authors: Oettl, R.; Hillebrandt, W.; Mueller, E. Bibcode: 1985A&A...151...33O Altcode: The collapse of a cool and dense interstellar cloud induced by a nearby supernova is studied. In the present model computations, the cloud is assumed to be initially spherically symmetric and in pressure equilibrium with the hot interstellar medium. In addition, the presence of a homogeneous magnetic field parallel to the direction from the supernova to the center of the cloud is assumed. The problem can then be treated by means of a two-dimensional magnetohydrodynamic code. The parameters which determine the model have been chosen in such a way that: (1) the cloud would be Jeans-stable without the supernova shock; (2) it would be compressed and collapse due to its self-gravity under the influence of a strong shock, if magnetic fields were absent. It is then found that a field of about 10 micro-G is required in order to prevent a cloud of 5000 solar masses and an average density of 8.3 x 10 to the -23rd g/cu cm from collapsing. These quantities correspond to a ratio of magnetic to gravitational energy of about 3, and a flux-to-mass ratio of roughly 12. For weaker fields, the cloud becomes gravitationally unstable and collapses. Title: Equilibrium models of differentially rotating polytropes and the collapse of rotating stellar cores Authors: Eriguchi, Y.; Mueller, E. Bibcode: 1985A&A...147..161E Altcode: Equilibrium models of axisymmetric, differentially rotating polytropes are used to estimate the properties of rotating stellar cores at the end point of their collapse. Results are presented for polytropes with adiabatic indices of 4.3, 1.32, 1.29, and 1.25. The results are in qualitative agreement with the results of earlier investigations, which did not allow for changes in the shape of the configuration, for the presence of density gradients, and for large differential rotation. The analysis shows that a rotating stellar core will not collapse all the way to neutron star densities on a dynamical time scale, if its initial ratio of rotational to gravitational energy is larger than some minimum value. The collapse stops due to rotation at an intermediate, dynamically stable, axisymmetric equilibrium state, and further evolution proceeds on a secular time scale. Title: A general computational method for obtaining equilibria of self-gravitating and rotating gases Authors: Eriguchi, Y.; Mueller, E. Bibcode: 1985A&A...146..260E Altcode: A general computational method is presented to compute equilibria of rapidly rotating self-gravitating gases. The superior capabilities of this method as compared to previously published methods stem from the fact that the equation of hydrostatic equilibrium and Poisson's equation are solved simultaneously with a Newton-Raphson iteration scheme. To demonstrate the capabilities of the method the authors have computed equilibrium sequences of differentially rotating polytropes for several rotation laws, and one equilibrium sequence using the ideal Fermi gas equation of state. Although in these examples the pressure is a function of the density only, a simple extension of the method allows to model closely more realistic temperature-dependent equations of state. Title: Equilibrium models of differentially rotating, completely catalyzed, zero-temperature configurations with central densities intermediate towhite dwarf and neutron star densities. Authors: Müller, E.; Eriguchi, Y. Bibcode: 1985MPARp.179.....M Altcode: No abstract at ADS Title: Personal reminiscences of Adriaan Blaauw (I) Authors: Müller, Edith A. Bibcode: 1985bems.symp..311M Altcode: No abstract at ADS Title: Density functional calculations of the ground state properties of atoms in strong magnetic fields. Authors: Kössl, D.; Wolff, R. G.; Müller, E.; Hillebrandt, W. Bibcode: 1985MPARp.205.....K Altcode: No abstract at ADS Title: Far-infrared-solar imaging from a balloon-borne platform Authors: Degiacomi, K.; Kneubuehl, F. K.; Huguenin, D.; Mueller, E. A. Bibcode: 1984IJIMW...5..643D Altcode: Far-infrared solar imaging with a balloonborne 60 cm-diameter Cassegrain telescope is described and related to previous solar observations in the millimeter range, the ir, vis and uv spectral regions. Solar images have been taken at 50 μm, 80 μm and 200 μm and represented as brightness temperature maps. The spectral windows observed correspond to the transition zone chromosphere-phocosphere of the solar atmosphere with a characteristic temperature minimum. Temperature enhancements of a few 100 K over the temperature of the quiet sun are reported for active solar regions, e.g. plages and sunspot regions. Far-infrared images provide less spatial resolution but more reliable temperature assignements than corresponding white-light, Ca II K and Hα pictures. Title: Equilibrium models of differentially rotating polytropes and the collapse of rotating stellar cores. Authors: Eriguchi, Y.; Müller, E. Bibcode: 1984MPARp.168.....E Altcode: No abstract at ADS Title: Neutrinos from collapsing stars. Authors: Hillebrandt, W.; Müller, E. Bibcode: 1984npa..conf..229H Altcode: Weak interaction processes leading to the production and emission of neutrinos from collapsing stars are reviewed. Based on recent numerical simulations of type II supernova explosions average electron neutrino energies and luminosities are computed. It is shown that typically a fast burst of neutrinos of energy 10 to 20 MeV and a luminosity of around 1054erg s-1 with a typical duration of a few ms is expected when the supernova shock reaches the neutrino sphere. Most of the neutrinos, however, are leaving the star on a much longer timescale with significantly lower average energies and luminosities. Title: Core Collapse Models of Type II Supernova Explosions Authors: Hillebrandt, W.; Müller, E. Bibcode: 1984ASIC..134..183H Altcode: 1984pcnr.conf..183H Core-collapse models of Type II supernova explosions are discussed. It is shown that stellar models with about 9 M_sun; on the main sequence do indeed lead to very energetic explosions, whereas more massive stars (M ≅ 20 M_sun;) so far do not explode. It is found, however, that the latter models are very close to mass ejection, and therefore future improvements of stellar models, input physics and numerical treatment may change these rather disappointing conclusions. Title: The Collapse of Rotating Stellar Cores: the Amount of Gravitational Radiation Predicted by Various Numerical Models Authors: Müller, E. Bibcode: 1984ASIC..134..271M Altcode: 1984pcnr.conf..271M The amount of gravitational radiation predicted by numerical calculations of the collapse of rotating stellar cores is reviewed. Currently the most realistic models suggest an energy loss of the order 10-6M_sun;c2. For a source situated at a distance of 10 Mpc (≈Virgo Cluster) the corresponding (dimensionless) wave amplitude h is smaller than 10-22, which seems to be even beyond the realm of the third generation gravitational wave detectors. On the other hand non-axisymmetric models predict up to 100 times larger radiative efficiencies. The uncertainties in these calculations are examined. Title: Variational calculation of iron and helium atoms and molecular chains in superstrong magnetic fields Authors: Mueller, E. Bibcode: 1984A&A...130..415M Altcode: The ground-state energy of iron atoms and molecular chains in superstrong magnetic fields (1-5 10 to the 12th Gauss) is recalculated. A 10 percent higher binding energy of the atoms and only a 1 percent higher binding energy of the molecular chains are found as compared to a previous investigation (Flowers et al., 1977). Therefore the calculations suggest that atoms are energetically more favorable than molecular chains in contradiction to the earlier results of Flowers et al. (1977). In addition, similar calculations for helium atoms and molecular chains have been performed. In this case it is found that, for B = 1 x 10 to the 12th Gauss the chains are bound with 50 eV relative to the free atoms. For B = 5 x 10 to the 12th Gauss the cohesive energy amounts to 190 eV. Title: Neutrinos from collapsing stars Authors: Müller, E. Bibcode: 1984npa..conf..229M Altcode: No abstract at ADS Title: Astronomy Education at Universities Authors: Muller, E. A. Bibcode: 1984aprm.conf..227M Altcode: No abstract at ADS Title: Carbon Combustion Supernovae Authors: Muller, E. Bibcode: 1983nuas.proc...40M Altcode: No abstract at ADS Title: Carbon combustion supernovae. Authors: Müller, E. Bibcode: 1983MPARp..90...40M Altcode: The author has performed a set of axisymmetric hydrodynamic numerical experiments of the core carbon flash, which incorporate the treatment of two-dimensional convection without the need of a phenomenological theory of convection. The numerical experiments show a variety of possible evolutions of degenerate carbon-oxygen cores ranging from spherical detonations to non-spherical deflagrations. Title: Gravitational Radiation from Collapsing Rotating Stellar Cores Authors: Muller, E. Bibcode: 1982ASIC...90..157M Altcode: 1982sscr.conf..157M No abstract at ADS Title: Numerical studies of nonspherical carbon combustion models Authors: Mueller, E.; Arnett, W. D. Bibcode: 1982ApJ...261L.109M Altcode: First results of axisymmetric numerical studies of the final evolution of degenerate C + O cores are reported. The two-dimensional convective flow is treated without a phenomenological theory of convection. The computations show that, in the beginning, the nuclear burning propagates slowly outward from the center of the star in a spherical combustion front. Small-scale eddies form, giving rise to bumps in the front. The bumps grow into blobs and eventually into fingers, which steadily elongate relative to the rest of the combustion front. This behavior is not well described by either the detonation or deflagration models, being more complex than either. Title: Gravitational radiation from collapsing rotating stellar cores Authors: Mueller, E. Bibcode: 1982A&A...114...53M Altcode: A post-Newtonian multipole formalism is invoked in a discussion of the gravitational radiation produced by the axisymmetric, Newtonian collapse models of rotating stellar cores examined by Mueller and Hillebrandt (1981). The results of calculations of waveforms and energy losses of the two lowest order multipoles, together with the energy spectrum of the quadrupole radiation, indicate that the gravitational wave signals from supernovae are weaker than earlier, less sophisticated collapse calculations suggested. Total energy loss in the form of gravitational waves is less than 0.000001 of the product of solar mass and c-squared, even for rapidly rotating stellar cores, and for a source located at a distance of 10 Mpc, the corresponding dimensionless wave amplitude is smaller than 10 to the -22nd. Title: Computer simulations of stellar collapse and shock wave propagation Authors: Hillebrandt, W.; Mueller, E. Bibcode: 1981A&A...103..147H Altcode: Using recent progress in deriving realistic equations of state of matter at high densities and temperatures, the gravitational collapse of cores of massive stars through core-bounce at neutron star densities is calculated. In particular, the sensitivity of the results is analyzed with respect to details of the equation of state, neutrino emissivities in the shock region, and properties of the hydrocode. In none of the cases considered is the core-bounce followed by an explosion of the stellar mantle. Although a shock forms in every case, it is never strong enough to accelerate matter beyond the escape velocity. The result is found to be independent of both the details of the equation of state and the assumptions about neutrino losses from the shocked matter. Title: The collapse of rotating stellar cores Authors: Mueller, E.; Hillebrandt, W. Bibcode: 1981A&A...103..358M Altcode: The collapse of the rotating cores of massive stars (M greater than or equal to 15 solar masses) is considered. The dynamical evolution of the core is followed by an explicit two-dimensional hydrodynamic code. A realistic, finite-temperature equation of state is used in the calculations. Rigidly and differentially rotating initial models are both studied. It is found that in all cases considered the collapse proceeds up to nearly nuclear matter density before it is stopped. In none of the examined models is the core-bounce followed by an explosion. The dynamical behaviour of the slowly rotating models is very similar to that of nonrotating models. The rapidly rotating cores already show large nonspherical effects before core bounce. In these models, a high entropy blob is formed near the axis of rotation, which, while trying to rise and expand, is rapidly destroyed by the onset of circulation. A flattened, nearly hydrostatic central condensation builds up with relatively low central density on which the matter of the envelope is further accreted. Title: Numerical Studies of the Non-spherical Core Carbon Flash Authors: Müller, E.; Arnett, W. D. Bibcode: 1981BAAS...13..791M Altcode: No abstract at ADS Title: Far-IR observations of active regions at sunspots with a balloon-borne 60 cm telescope. Authors: Cartier, F.; Kneubühl, F.; Huguenin, D.; Müller, E. A. Bibcode: 1981imw..conf..W31C Altcode: No abstract at ADS Title: A comparison between the observed and predicted UV line blocking for blanketed model atmospheres of early type stars Authors: Castelli, F.; Lamers, H. J. G. L. M.; de Andres, F. L.; Mueller, E. A. Bibcode: 1980A&A....91...32C Altcode: For early B main-sequence and giant stars the observed near-UV blocking factors are larger than those predicted by blanketed model atmospheres with a microturbulence of 2 km/sec. Better agreement would be reached if a microturbulence of 4 to 5 km/sec were adopted. Evidence was found that the line opacities due to doubly ionized metals are unsufficiently accounted for in the model atmospheres. For late B main-sequence and giant stars the observed near-UV blocking is smaller than predicted which points to an over-estimation of the line opacities due to singly ionized metals. The observed blocking in early B supergiants is much larger than predicted and would require a microturbulence of 10 km/sec at least. If this large blocking extends to the far UV, the energy distribution given by the models might be changed drastically. Title: Book-Review - IAU Transactions V.17A - Reports on Astronomy Authors: Muller, E. A.; Tayler, R. J. Bibcode: 1980Obs...100..131M Altcode: No abstract at ADS Title: Variability of the far-infrared solar temperature minimum with the solar cycle Authors: Mueller, E. A.; Kneubuehl, F. K.; Rast, J.; Stettler, P. Bibcode: 1980A&A....87L...3M Altcode: Measurements of the absolute solar brightness temperature in the far-infrared, carried out since 1971 with a balloon-borne lamellar-grating interferometer, have revealed (1) a flat minimum of the temperature profile in the spectral range between 60 and 100 kaysers, and (2) a variation of the temperature minimum with time. It is shown here that the variation of the solar temperature minimum observed from 1971 to 1978 is systematic and congruent with the variation of the yearly mean of the Zuerich Relative Sunspot Numbers over the same period of time. This suggests that the value of the solar temperature minimum varies with the solar cycle. Title: Measurement of the absolute solar brightness temperature in the far-infrared with a balloon-borne interferometer Authors: Rast, J.; Cartier, F.; Kneubuehl, F. K.; Huguenin, D.; Muller, E. A. Bibcode: 1980A&A....83..199R Altcode: The absolute solar brightness temperature was measured with a stratospheric balloon-borne lamellar-grating interferometer in the spectral region 15 cm-1 to 100 cm-1 on the occasion of two flights. The results are compared with previous measurements and the models of the solar atmosphere by Vernazza et al. (1976). Title: Stellar collapse - Adiabatic hydrodynamics and shock wave propagation Authors: Mueller, E.; Hillebrandt, W.; Rozyczka, M. Bibcode: 1980A&A....81..288M Altcode: The consistency of the shock wave description in an adiabatic approximation of supernova explosions (Van Riper, 1978) is examined. It is shown that shock propagation cannot be simulated correctly and that whether or not mass is ejected from the rebounding core strongly depends on the treatment of energy dissipation in the shock. It appears therefore that the question of whether purely hydrodynamic effects can cause supernova explosions cannot be answered with the help of adiabatic models. This conclusion remains valid for two-dimensional (i.e. axisymmetric) simulations of the collapse of rotating configurations. On the other hand, the experiments in two dimensions show some new interesting effects which do not depend on the treatment of the shock front. Title: Book-Review - Reports on Astronomy Authors: Muller, E. A. Bibcode: 1980S&T....59T.154M Altcode: No abstract at ADS Title: Measurement of the spectrum of the sun in the far infrared. Authors: Rast, J.; Cartier, F.; Kneubühl, F.; Huguenin, D.; Mueller, E. A. Bibcode: 1980AcHPh..52..400R Altcode: No abstract at ADS Title: Introduction, by the CHAIRMAN Authors: Müller, Edith A. Bibcode: 1980fsoo.conf..181M Altcode: No abstract at ADS Title: On Asymmetries of Solar Spectral Lines Authors: Barambon, C.; Mueller, E. A. Bibcode: 1979SoPh...64..201B Altcode: The profiles of 43 lines have been observed at the centre and near the limb of the solar disk. Their asymmetry decreases towards the limb, and increases with the equivalent width and the mean heigth of line formation; no relation was found between the asymmetry and the line excitation potential, nor with the degree of ionization, nor with the usually adopted macroturbulent velocity. The asymmetry appears to be due to radial movements. Title: A magnetohydrodynamical supernova model. Authors: Mueller, E.; Hillebrandt, W. Bibcode: 1979A&A....80..147M Altcode: A model for supernova explosions of massive stars in which mass ejection is caused by a two-step process is presented. In the first stage the rebounce of the core at nuclear density generates a hydrodynamical shock wave; if this shock is not sufficient for mass ejection reimplosion of the stellar mantle results. During collapse the core spins much more rapidly than the mantle amplifying the magnetic field by winding the magnetic field lines. For sufficiently large initial magnetic field strength values the magnetic pressure becomes comparable to the thermal pressure in a small region near the collapsed core, pushing the matter outwards, and thus generating a second magnetohydrodynamical shock. Results showed mass ejection with energies of about several times 10 to the 50th power erg leaving behind a neutron star of approximately 1-1.5 solar mass. Title: Line blocking in the near ultraviolet spectrum of early type stars. II. The dependence on spectral type and luminosity for normal stars. Authors: Llorente de Andres, F.; Lamers, H. J. G. L. M.; Muller, E. A. Bibcode: 1979A&AS...38..367L Altcode: The variation with luminosity and spectral type of the line blocking in the near-UV spectrum of "normal" O8 to A2 stars is studied. In the 2500 A and the 2800 A region the blocking increases from O8 to A2 due to lines of singly ionized metals. In the 2100 A region the blocking reaches a maximum at B0.5 for main-sequence stars, at B2 for giants and at B3 for supergiants, which is due to lines of twice ionized metals. The blocking in supergiants is about twice as large as in main-sequence stars; this can be explained by the larger microturbulent velocity of about 10 km/s in supergiants. A few "normal" stars were found to have an anomalous UV-blocking. Key words: Ultraviolet spectrum Early type stars - Line blocking Title: A magnetohydrodynamic supernova model Authors: Mueller, E. Bibcode: 1979PhDT.........2M Altcode: A quasi-spherical model is developed for the supernova explosion of a massive rotating magnetic star. The dynamic development that leads to the explosion is represented in three phases: the collapse phase, the field intensification phase, and the explosion phase. Numerical results show that the explosion leads to the ejection of masses with energies of 10 to the 50th erg, leaving behind a rotating magnetic neutron star with a mass of 0.8-1.5 solar masses. A physical description and mathematical formulation of the model are given and calculations are presented with and without consideration of the magnetic field. Title: Minimum far infrared solar brightness temperature and sunspot activity. Authors: Kneubühl, F. K.; Rast, J.; Stettler, P.; Muller, E. A.; Huguenin, D. Bibcode: 1979imwa.conf..177K Altcode: No abstract at ADS Title: Reports on Astronomy. Authors: Müller, E. A. Bibcode: 1979IAUTA..17.....M Altcode: No abstract at ADS Title: International Astronomical Union, Information Bulletin. No. 41. Authors: Müller, E. A. Bibcode: 1979IAUIB..41.....M Altcode: No abstract at ADS Title: Measurement of the solar brightness temperature near its minimum with a balloon-borne lamellar-grating interferometer. Authors: Rast, J.; Kneubuhl, F. K.; Muller, E. A. Bibcode: 1978A&A....68..229R Altcode: For the measurement of the absolute solar brightness temperature in the far-infrared, an improved balloon-borne lamellar-grating interferometer and a blackbody calibration source were built. During the first two flights in 1975/76 a flat temperature profile was observed between 60 and 110 kaysers, with a minimum of 4530 K plus 100 K/-150 K. The accuracy of this measurement permits a decision to be made in favor of the present models of the solar atmosphere. From the measured residual terrestrial absorption above 33.5 km an average water-vapor volume mixing ratio of 6.3 plus or minus 1.6 ppm is determined. Title: Line blocking in the near ultraviolet spectrum of early type stars. I. Observed blocking factors for 132 stars. Authors: Lamers, H. J. G. L. M.; Mueller, E. A.; Llorente de Andres, F. Bibcode: 1978A&AS...32....1L Altcode: The line blocking factors in the ultraviolet spectrum of 132 stars of types O4 to A7 observed by the S59 experiment are presented. The blocking factors are given for intervals of 10 A wide in the wavelength ranges of 2070-2150 A, 2505-2585 A and 278() 2860 A as well as for these whole intervals. The accuracy of the blocking factors is given in terms of a 2o error. The intrinsic continuum colors - , - , and rn2500- V0 are also given. Title: Transport of angular momentum by magnetic fields during the gravitational collapse of rotating massive stars Authors: Hillebrandt, W.; Mueller, E. Bibcode: 1978MitAG..43..236H Altcode: No abstract at ADS Title: Transport of Angular Momentum by Magnetic Fields During the Gravitational Collapse of Rotating Massive Stars Authors: Hillebrandt, W.; Müller, E. Bibcode: 1978MitAG..43Q.236H Altcode: No abstract at ADS Title: International Astronomical Union, Information Bulletin. No. 40. Authors: Müller, E. A. Bibcode: 1978IAUIB..40.....M Altcode: No abstract at ADS Title: International Astronomical Union, Information Bulletin. No. 39. Authors: Müller, E. A. Bibcode: 1978IAUIB..39.....M Altcode: No abstract at ADS Title: Variational calculation of ground-state energy of iron atoms and condensed matter in strong magnetic fields. Authors: Flowers, E. G.; Ruderman, M. A.; Lee, J. -F.; Sutherland, P. G.; Hillebrandt, W.; Mueller, E. Bibcode: 1977ApJ...215..291F Altcode: Variational calculations of the binding energies of iron atoms and condensed matter in strong magnetic fields (greater than 10 to the 12th gauss). These calculations include the electron exchange energy. The cohesive energy of the condensed matter, which is the difference between these two binding energies, is of interest in pulsar theories and in the description of the surfaces of neutron stars. It is found that the cohesive energy ranges from 2.6 keV to 8.0 keV. Title: Space missions to the moon and planets. Joint discussion at the XVIth General Assembly of the I.A.U., Grenoble, 1976. Authors: Müller, E. A. Bibcode: 1977smmp.conf.....M Altcode: No abstract at ADS Title: Highlights of Astronomy, Vol._4, Parts I and II. as presented at the XVIth General Assembly of the I.A.U., Grenoble, 1976. Authors: Müller, E. A. Bibcode: 1977havp.book.....M Altcode: No abstract at ADS Title: Transactions of the International Astronomical Union, Volume XVI B: Proceedings of the Sixteenth General Assembly, Grenoble 1976. Authors: Müller, E. A.; Jappel, A. Bibcode: 1977tiau.book.....M Altcode: No abstract at ADS Title: Highlights of astronomy. Volume 4 - International Astronomical Union, General Assembly, 16th, Grenoble, France, August 24-September 2, 1976, Proceedings. Parts 1 & 2 Authors: Mueller, E. A. Bibcode: 1977HiA.....4.....M Altcode: The papers deal with space missions to the moon and planets, X-ray binaries and compact objects, clusters of galaxies, space astrometry, Galactic structure toward the poles, the small-scale structure of solar magnetic fields, the impact of UV observations on stellar spectral classification, and observational evidence for heterogeneities on stellar surfaces. Specific topics include IR observations of interstellar dust, a review of in situ planetary observations by spacecraft, transient X-ray sources, X-ray bursts, the evolutionary history of X-ray binaries, accretion flows in binary X-ray systems, the magnetic field of Mercury, and lunar magnetism. Other papers examine cratering of terrestrial planets, the dynamical evolution of clusters of galaxies, X-rays from clusters of galaxies, hot gas in clusters, the microwave background radiation toward various clusters, the Large Space Telescope astrometric instrument, and the space density of M dwarfs. The Galactic mass density in the vicinity of the sun is also discussed as well as the distribution of field horizontal-branch stars in the Galactic halo, polarization measurements and extinction near the North Galactic Pole, the decay of light elements in stellar envelopes, observations of solar small-scale photospheric magnetic fields, EUV observations of white dwarfs, and an atlas of UV stellar spectra. Title: The Solar Brightness Temperature in the Far Infrared (Abstract) Authors: Müller, E. A.; Stettler, P.; Rast, J.; Kneubühl, F. K.; Huguenin, D. Bibcode: 1977ASSL...63..107M Altcode: 1977isa..symp..107M No abstract at ADS Title: De Internationale Astronomische Unie. Authors: Müller, E. A. Bibcode: 1977Zenit...4...42M Altcode: No abstract at ADS Title: International Astronomical Union, Information Bulletin. No._37. Authors: Müller, E. A. Bibcode: 1977IAUIB..37.....M Altcode: No abstract at ADS Title: International Astronomical Union, Information Bulletin. No._38. Authors: Müller, E. A. Bibcode: 1977IAUIB..38.....M Altcode: No abstract at ADS Title: International Astronomical Union, General Assembly, 16th, Grenoble, France, August 24-September 2, 1976, Proceedings Authors: Mueller, E. A.; Jappel, A. Bibcode: 1977IAUTB..16.....M Altcode: 1977IAUT...16.....M Resolutions adopted by the General Assembly of the International Astronomical Union are considered, taking into account astronomical constants, astronomy and astrophysics abstracts, atomic and molecular data, the international solar system program, polar motion, the protection of the radio spectrum and observatory sites, and the resolutions adopted by the commissions. Reports of meetings of commissions are also presented, giving attention to ephemerides, documentation, astronomical telegrams, celestial mechanics, positional astronomy, instruments and techniques, solar activity, radiation and structure of the solar atmosphere, comets and meteorites, planets and satellites, the moon, the rotation of the earth, the light of the night sky, photographic astrometry, stellar photometry and polarimetry, double stars, variable stars, galaxies, stellar spectra, radial velocities, time, interstellar matter and planetary nebulae, stellar constitution, star clusters, and cosmology. Title: Matter in superstrong magnetic fields and the structure of a neutron star's surface. Authors: Hillebrandt, W.; Mueller, E. Bibcode: 1976ApJ...207..589H Altcode: The properties of matter in strong and superstrong magnetic fields (B 5 x gauss) are reconsidered. By slightly improving and correcting previous calculations it is shown that molecular chains are only slightly bound with respect to free atoms. For B = 1012 gauss the cohesive energy is 0.11 keV and 0.29 keV for iron and carbon, respectively. Only at extremely high magnetic fields (B > 5 x 10' gauss), which are probably not present in pulsars, do we get strong binding (>10 keV). Subject headings: dense matter - magnetic fields - stars: neutron Title: The solar brightness temperature in the far infrared Authors: Mueller, E. A.; Huguenin, D.; Stettler, P.; Rast, J.; Kneubuehl, F. K. Bibcode: 1976cosp.meetR....M Altcode: Measurements of absolute solar brightness have been obtained for a wide range of far-infrared and submillimeter wavelengths using a balloon-borne lamellar grating interferometer. An experiment covering the wavelength range 200-600 microns showed that at 200 microns the solar brightness temperature may reach a value of about 4100 K, a result not incompatible with the higher values of the temperature minimum derived from ultraviolet observations around 1600 A. The brightness temperature is constant between about 95 and 200 microns, corresponding to the flat temperature minimum of the photosphere/chromosphere transition region. Some of the spectra obtained have a spectral resolution better than 0.5/cm, allowing the detection of a number of stratospheric molecular absorption lines (H2O, O2, O3). Title: Properties of matter in strong and superstrong magnetic fields. Authors: Müller, E.; Hillebrandt, W. Bibcode: 1976MitAG..38..120M Altcode: No abstract at ADS Title: Measurement of the solar brightness temperature between 85 and 250 µ with a balloonborne lamellar grating interferometer. Authors: Rast, J.; Kneubühl, F.; Müller, E. A. Bibcode: 1976AcHPh..49..754R Altcode: No abstract at ADS Title: The solar beryllium abundance. Authors: Chmielewski, Y.; Brault, J. W.; Mueller, E. A. Bibcode: 1975A&A....42...37C Altcode: An interpretation of high-resolution centerlimb observations of the Be II resonance lines in the solar spectrum is given. It is shown that to account for the observed spectrum, it is necessary to allow for (1) a source of additional opacity in the UV continuum which was derived empirically for the HSRA (Harvard Smithsonian Reference Atmosphere) and revised Holweger (1974) models and (2) departures from LTE in the Be I-Be II system. It is found that the 2p(3)P(0) metastable level of Be I is significantly underpopulated and that beryllium is more ionized than expected in the case of local thermodynamic equilibrium. The kinetic equilibrium calculations yield a logarithmic beryllium abundance of approximately 1.15 (on the basis of a logarithmic hydrogen abundance of 12.00), which is in agreement with previous determinations based on the LTE assumption. Title: Matter in superstrong magnetic fields and the structure of a neutron star's surface Authors: Hillebrandt, W.; Mueller, E. Bibcode: 1975STIN...7625119H Altcode: The properties of matter in strong and superstrong magnetic fields (B in the range of 5 x 10 to the 11th power to 10 to the 13th power Gauss) are reconsidered. By slightly improving and correcting previous calculations it is shown that molecular chains are only slightly bound with respect to free atoms. For B = 10 to the 12th power Gauss the cohesive energy is 0.07 keV and 0.19 keV for iron and carbon respectively. Only at extremely high magnetic fields (B greater than or equal to 5 x 10 to the 14th power Gauss), which are probably not present in pulsars, strong binding is obtained (greater than 10 keV). Title: The Potassium Abundance in the Solar Photosphere Authors: de La Reza, R.; Mueller, E. A. Bibcode: 1975SoPh...43...15D Altcode: High precision center-limb spectrograms of the K I resonance doublet line at λ 7699 Å were used to study the line formation and to determine the abundance of potassium in the solar atmosphere. The LTE assumption is not valid for these lines. Synthetic profiles computed in NLTE reproduce very well the observed center-limb line behaviour and yield logɛK = 5.14±0.10 for the solar abundance of potassium (on the scale of logɛH = 12 for Hydrogen). Title: The Solar Lithium Abundance. I: Observations of the Solar Lithium Feature at λ 6707.8 Å Authors: Brault, J. W.; Mueller, E. A. Bibcode: 1975SoPh...41...43B Altcode: A detailed observational study of the solar photospheric lithium feature has been carried out with emphasis on center-limb observations, continuum location, possible effects of telluric lines, effects of blending by atomic and molecular lines, and decomposition of the solar spectrum around λ6707 Å. Title: The Solar Lithium Abundance. II: Synthetic Analysis of the Solar Lithium Feature at λ 6707.8 Å Authors: Müller, Edith A.; Peytremann, Eric; de la Reza, Ramiro Bibcode: 1975SoPh...41...53M Altcode: The solar abundance of lithium and its isotopic abundance ratio were determined by comparing synthetic spectra with the high quality center-to-limb spectra of the solar lithium feature presented in Paper I by Brault and Müller (1974). The following possible effects on the abundance result were considered: deviations from LTE, atmospheric models, blends by molecular and atomic lines, hyperfine structure, large scale velocity fields. It was found that the photospheric lithium abundance is logɛLi=1.0±0.1. The greatest uncertainty is due to differences in the atmospheric models. The NLTE abundance result is 0.05 dex smaller than the LTE value. A mean depth of line formation was determined for the Li7I λ16707.776 Å line. The lithium isotopic abundance ratio was found to be Li6/Li7⩽0.01. Title: Far-Infrared Solar Brightness Measured with a Balloon-Borne Lamellar-Grating Interferometer Authors: Stettler, P.; Rast, J.; Kneubuehl, F. K.; Mueller, E. A. Bibcode: 1975SoPh...40..337S Altcode: The solar brightness temperature was measured at wavelengths between 208μ and 660μ with a lamellar-grating interferometer. In order to avoid terrestrial absorption due to water vapor the measurement of the absolute spectral brightness was performed at altitudes of 30 km and 35 km with a balloon borne gondola. A cylindrical black body radiation source served as absolute calibration standard. Its wall temperature lay between 1100 K and 1300 K. Since the box of the interferometer and the black body could not be evacuated for the calibration, the air in the system was replaced by dry nitrogen. Nevertheless, residual water vapor absorption lines hampered the precision of the absolute calibration. The corresponding error could not be reduced to less than ±100 K. The present experimental temperature profile is compared to results obtained from other measurements. The results agree with the empirical HSRA model and with those of other research groups in the spectral range between 208μ and 660μ. Title: Book reviews Authors: van de Stadt, Herman; Rawer, Karl; Schadee, A.; Noyes, R. W.; Bleeker, J. A. M.; Wittenberg, H.; de Graaff, W.; Akasofu, S. -I.; Hooykaas, R.; Bappu, M. K. V.; Atanasijević, I.; Icke, Vincent; van der Valk, F.; Kresàk, L.; Müller, Edith A. Bibcode: 1975SSRv...17..159V Altcode: No abstract at ADS Title: The solar brightness temperature in the far infrared. Authors: Müller, E. A.; Stettler, P.; Rast, J.; Kneubühl, F. K.; Huguenin, D. Bibcode: 1975MmArc.105...90M Altcode: No abstract at ADS Title: The solar brightness temperature in the far infrared Authors: Müller, E. A.; Stettler, P.; Rast, J.; Kneubühl, F. K.; Huguenin, D. Bibcode: 1975cesra...5...90M Altcode: No abstract at ADS Title: The Photospheric Barium Spectrum: Solar Abundance and Collision Broadening of Ba II Lines by Hydrogen Authors: Holweger, H.; Mueller, E. A. Bibcode: 1974SoPh...39...19H Altcode: A study of the solar Ba II spectrum leads to a solar abundance of barium of logεBa = = 2.11±0.12, on the scale logεH = 12. The observed asymmetry of the resonance line λ4554 is consistent with an isotopic abundance ratio equal to the terrestrial one. The meteoritic Ba/Si abundance ratio found in carbonaceous chondrites appears to exceed the solar ratio by 0.1 to 0.2 dex (Section 5). Title: Vacation courses in astronomy for graduates and teachers. Authors: Müller, E. A. Bibcode: 1974Obs....94..110M Altcode: No abstract at ADS Title: Submillimeter-wave solar brightness temperature measured with a balloon-borne lamellar-grating interferometer. Authors: Stettler, P.; Rast, J.; Kneubühl, F.; Müller, E. A. Bibcode: 1974swa..conf..163S Altcode: No abstract at ADS Title: Teaching of astronomy (Enseignement de l'astronomie). Authors: Müller, E. A. Bibcode: 1973IAUTA..15..717M Altcode: No abstract at ADS Title: Absolute Measurement of the Solar Brightness in the Spectral Region between 100 and 500 Microns Authors: Stettler, P.; Kneubuh, F. K.; Muller, E. A. Bibcode: 1972A&A....20..309S Altcode: Summary. The solar brightness temperature at wavelengths between 110 and 500 was measured with a balloon-borne lamellar-grating interferometer. A high temperature black body served as absolute calibration source. The experimental results are compared with those of other research groups and with the empirical HSRA model. The agreement with the model is fairly good for wavelengths greater than 300 t. Key words: sun - far-infrared - interferometry - stratosphere Title: International conference on education in and history of modern astronomy. held at the American Museum of Natural History on August 30 and 31 and September 1, 1971. Authors: Berendzen, R.; Müller, E. A. Bibcode: 1972NYASA.198..275B Altcode: No abstract at ADS Title: The Commission on the Teaching of Astronomy of the International Astronomical Union. Authors: Mueller, E. A. Bibcode: 1972NYASA.198...66M Altcode: No abstract at ADS Title: Teaching of Astronomy (Enseignernent de 1'Astronomie) Authors: Müller, E. A. Bibcode: 1971IAUTB..14..236M Altcode: No abstract at ADS Title: Teaching of astronomy. Authors: Müller, E. A. Bibcode: 1970IAUTA..14..559M Altcode: No abstract at ADS Title: Astronomy education material (Prepared by I.A.U. Commission 46 - Teaching of Astronomy). Authors: Müller, E. A. Bibcode: 1970aem..book.....M Altcode: No abstract at ADS Title: Book reviews Authors: Nicolet, M.; Müller, Edith A.; de Jager, C.; Rutten, H. S.; Millman, P. M.; Fielder, G. Bibcode: 1969SSRv...10..314N Altcode: No abstract at ADS Title: Lithium Observations in the Sun Authors: Müller, Edith A. Bibcode: 1968HiA.....1..243M Altcode: No abstract at ADS Title: Center-to-Limb Analysis of the Solar Oxygen Lines Authors: Müller, Edith A.; Baschek, Bodo; Holweger, Hartmut Bibcode: 1968SoPh....3..125M Altcode: Several lines of neutral oxygen observed at various positions on the solar disk were used to study the influence of (1) the temperature distribution, (2) the velocity field, and (3) the damping on the line profiles and the abundance of oxygen in the photosphere. Theoretical profiles were calculated on the basis of four different model atmospheres in LTE. It was found that the model proposed by HOLWEGER (1967) best reproduced the center-to-limb observations of the lines studied. The weighted mean of the oxygen abundance turned out to be log ɛO = 8.83 on the basis of log ɛH = 12.00. Title: The Composition of the Solar Atmosphere Authors: Müller, E. A. Bibcode: 1967sp...conf...33M Altcode: No abstract at ADS Title: A Critical Discussion of the Abundance Results in the Solar Atmosphere Authors: Müller, E. A. Bibcode: 1966IAUS...26..171M Altcode: No abstract at ADS Title: Effects of Deviations from Local Thermodynamic Equilibrium on Solar Abundances Authors: Muller, Edith A.; Mutschlecner, J. Paul Bibcode: 1964ApJS....9....1M Altcode: Investigations of center-to-limb variations of curves of growth were carried out in order to detect effects of deviations from local thermodynamic equilibrium on solar abundances. The neutral stages of the elements Ca, Ti, V, Cr, Mn, Fe, and Co were considered. For three positions on the solar disk, = 1.0, 0.5, and 0.3, theoretical curves of growth were computed by the weighting-function method employing a new semi-empirical solar model and new partition functions. The observed curves of growth were constructed with the most reliable f-values available and with equivalent widths measured on three solar spectrum atlases of the McMath-Hulbert Observatory of the University of Michigan traced at the three values of . No systematic variation of the abundances from center to limb or from lower to higher excitation lines could be detected. This indicates that the assumption of local thermodynamic equilibrium does not introduce large errors in the solar abundances of the elements in the iron group. The high quality of the observational and theoretical data employed in this investigation should make possible reliable results for the abundances of the elements in the iron group. The choice of the absolute f-value scale is still very questionable, however, and completely trustworthy abundances cannot yet be obtained. Title: Center-Limb Effects on Solar Abundances. Authors: Müller, Edith A.; Mutschlechner, J. Paul Bibcode: 1962AJ.....67T.277M Altcode: Several investigators have pointed out that deviations from local thermodynamic equilibrium (LTE) can introduce large differences between the electron temperature and the excitation temperature. Accordingly, for photospheric models that neglect deviations from LTE one might expect large discrepancies in the abundance of an element when the calculations are based on lines that are formed in different layers of the photosphere, i.e.,lines observed at different points on the solar disk and lines of different excitation potentials. The purpose of this investigation has been to determine whether or not such discrepancies exist for elements in the iron group, and if they do exist, to determine their magnitude. The elements of the iron group were chosen for investigation because (a) for these elements a number of faint and medium-strong lines of different excitation potential are observed in the solar spectrum, and (b) reliable experimental relative f values are available. The lines were observed at the three positions on the solar disk ~-- 1.0, 0.5, and 0.3 with the vacuum spectrograph at the MeMath-Hulbert Observatory by Dr. Mohler and his associates. The equivalent widths of blended lines were determined by the Utrecht method. A homogeneous model of the photosphere, assuming LTE, was employed in which the recently observed temperature distributions are included. The theoretical calculations of the equivalent widths by the weighting function method were carried out with the aid of the IBM 704 computer of The University of Michigan. Individual curves of growth were calculated for each element for various sets of wavelengths and excitation potentials. The observed lines of each element were separated into groups according to their excitation potentials. For each element and for each position on the solar disk, the individual groups of lines were plotted separately on a curve of growth diagram and individual abundances derived. No systematie variation of the abundances from center to limb or from lower to higher excitation lines could be detected. This result indicates that the assumption of LTE in the photospheric model does not introduce great discrepancies in the solar abundances of the elements in the iron group. This work was supported in part by Contract Nonr-1224(19), NR 015-320 with the Office of Naval Research. Title: The Abundances of the Elements in the Solar Atmosphere. Authors: Goldberg, Leo; Muller, Edith A.; Aller, Lawrence H. Bibcode: 1960ApJS....5....1G Altcode: The method of weighting functions has been utilized to derive the abundances of forty-two elements from faint and medium-strong lines in the solar spectrum. The model atmosphere adopted is that of Aller and Pierce as extended by Elste to both higher and deeper layers. The chief sources of equivalent widths were the measurements by Allen and by the Utrecht astronomers, but a substantial number of new measurements were included from McMath-Hulbert Observatory data. TheJ-values were taken from many different sources, but, whenever possible, experimental measurements were employed. When laboratory data were not available, they were replaced by theoretical values based on the assumption of LS coupling and making use of the f-sum rule or of the Bates and Damgaard tables for the absolute scale factor. A detailed description is given of the derivation of the abundance of each element, including the major sources of uncertainty, such as the errors in the measurement of weak lines throughout the spectrum and of all lines in the ultraviolet region, uncertainties in the solar model for ultraviolet lines, and the unreliable character of many of the f-values employed. Title: The Double Reversal in the Cores of the Fraunhofer H and K Lines. Authors: Goldberg, Leo; Mohler, O. C.; Müller, Edith A. Bibcode: 1959ApJ...129..119G Altcode: Observations are presented of the profiles of the central doubly reversed cores of the H and K lines of Ca ii in the Fraunhofer spectrum. The profiles were obtained photoelectrically with the vacuum spectograph of the McMath-Hulbert Observatory at five different points on the solar disk from M = 1.0 to = 0.2. At the center of the disk the central intensities of H and K are 2.95 and 2.36 per cent, respectively, in terms of the neighboring continuous spectrum near X 4000. At = 0.2 the central intensities are 2.41 and 2.01 per cent for H and K, respectively, also with reference to the continuum at X 4000 at the center of the disk. The relative intensity ratio H: K is found to be constant in the inner absorption core and nearly the same for all values of . This suggests that the logarithm of the source function varies linearly with the logarithm of Nh, the number of Ca ii atoms per square centimeter above height, h, in the chromosphere. The Doppler widths were derived by two methods, namely, (1) by an intercomparison method which is independent of the source functiop and (2) by using the depth-dependence of the source function and the shapes of the profiles. The Doppler widths thus found increase from 0.063 A at = 1.0 to 0.110 A at = 0.2. The derived Doppler widths and source function are employed to calculate the profiles of the inner cores of H and K. Extremely good agreement is found between the calculated and the observed central cores at all five values of . The variation in the Doppler widths from center to limb is discussed, and it is concluded that the widening of the profiles to the limb is caused by an increase in turbulence with height, combined with anisotropy. The comparison of the Doppler widths derived for Ca ii with results previously obtained for the X 10830 line of He I supports the hypothesis that the chromosphere is heterogeneous and is composed of regions of quite different physical properties. Title: The Profile of Hα during the Limb Flare of February 10, 1956. Authors: Goldberg, Leo; Mohler, Orren C.; Muller, Edith A. Bibcode: 1958ApJ...127..302G Altcode: Profiles of the Ha line in a very bright loop prominence associated with the great limb flare of February 10, 1956, show pronounced violet asymmetries. Despite the fact that the centers of different profiles, made at several points in the line on two different exposures, exhibit relative Doppler displacements as high as 0.8 A, the shapes of all the profiles can be accounted for by the superposition on the main Ha profile of an additional component centered between 1.5 and 2.0 A to the violet. The possibility is discussed that the asymmetry may have been caused by the presence of abnormal amounts of deuterium, presumably generated by nuclear reactions during the flare event. It is concluded that, although the evidence for deuterium is not conclusive, it would be extremely important to observe other similar flareassociated prominences in the future, with modern high-dispersion spectrographs. Observations should also be made simultaneously on at least one additional line of an element other than hydrogen, in order to eliminate velocity effects. Title: The chemical composition of the solar atmosphere. Authors: Goldberg, Leo; Muller, Edith A.; Aller, Lawrence H. Bibcode: 1957AJ.....62R..15G Altcode: The abundances of some 40 elements relative to hydrogen have been redetermined in a new investigation of the chemical composition of the solar atmosphere from the Fraunhofer spectrum. The measi~irements of equivalent widths by the Utrecht group and by Allen's have been supplemented by infrared data and by measurements of selected lines on vacuum spectrograph plates from the McMath-Hulbert Observatory. The method of analysis is that of weighting functions, as developed by Minnaert and Claas for weak lines and by Pecker for lines of medium strength. In this method, the equivalent width of each line is related to the abundance by an integral over the model atmosphere, in which the integrand is the product of the number of absorbing atoms, the weighting function at each point in the atmosphere, and a so-called saturation function which reduces to unity for weak lines. Special numerical techniques for the evaluation of these integrals have been devised by Elste and adapted by him for computation with the Michigan high-speed computers, MIDAC and the IBM 650. An extensive set of these integrals has been tabulated by Elste for both weak lines and those of medium strength covering the wave-length region XX4ooo to 22,000 and a wide range of excitation potentials. This tabulation has provided the basis for the present investigation of solar abundances. The model atmosphere employed was derived by Waddell and Pierce from the latter's recent observations of solar-limb darkening and spectral- energy distribution, but with the pressure distribution modified by Elste in accordance with the work of Weidemann. The results are generally in good agreement with those of other workers, but there are notable exceptions, especially for those abundances that depend on the analysis of lines of medium strength. The reason appears to be that the shape of the curve of growth in the transition region differs markedly for lines originating at different depths in the atmosphere. It is anticipated that the results quoted here can be further improved when new photoelectric observations of weak lines are secured with the vacuum spectrograph of the McMath-Hulbert Observatory. However, for a large number of elements, uncertainties in the f-values present the major obstacle to definitive abundance determinations. University of Michigan, Ann Arbor, Mich. Title: The origin of the double reversal in the Fraunhofer H and K lines. Authors: Goldberg, Leo; Muller, Edith A. Bibcode: 1957AJ.....62R..92G Altcode: The discovery by 0. C. Wilson of a correlation between the absolute magnitudes of the G, K and M stars and the widths of the emission reversals in their K-line cores emphasizes the importance of establishing the mechanism both for widening the H and K emission-line cores in the sun and for producing the central self-reversal. Evidence is presented that favors Doppler broadening on the one hand and abundance broadening on the other. It is shown that the apparently conflicting arguments for the two kinds of broadening can be resolved if the cores of the H and K lines are formed in an optically-thick chromosphere in which the excitation temperature decreases with height. Methods are developed for the derivation of the excitation temperature and Ca+ density distributions from the observed profiles and it is shown that the resulting model accounts satisfactorily for the main features of the observed profiles both at the center of the disk and at the limb. University of Michigan Observatory, Ann Arbor, Mich. Title: The Abundances of the Elements in the Sun Authors: Goldberg, Leo; Aller, Lawrence H.; Müller, Edith A. Bibcode: 1955stat.conf..141G Altcode: 1954stat.conf..141G No abstract at ADS Title: Dreifarben-Photometrie des offenen Sternhaufens NGC 7510 und seiner Umgebung. Mit 10 Textabbildungen. Authors: Becker, W.; Müller, E. A.; Stenlin, U. Bibcode: 1955ZA.....38...81B Altcode: No abstract at ADS Title: Dreifarben-Photometrie des offenen Sternhaufens NGC 654 und einer benachbarten Sterngruppe. Mit 5 Textabbildungen Authors: Müller, E. A. Bibcode: 1955ZA.....38..110M Altcode: No abstract at ADS Title: The Width of Hα in Solar Flares. Authors: Goldberg, Leo; Dodson, Helen W.; Müller, Edith A. Bibcode: 1954ApJ...120...83G Altcode: It is shown that the observed large widening, at or near maximum, of the Ha emission line in certain solar flares can be explained as a consequence of radiation damping and the high abundance of two- quantum H atoms in the line of sight. When the effective width `of the Ha line is calculated according to the theory of self-absorption, the assumption of radiation damping leads to agreement with the observed lines widths when the number of two-quantum H atoms lies in the approximate range per cm2 in the line of sight. If it is assumed that the lateral extension of a flare is large compared with its thick- ness, the theory predicts that the effective width of Ha should be proportional to the square root of sec 0, where 0 is the angular distance from the center of the solar disk. Study of the Ha line widths of 610 flares reported in the Quarterly Bulletin of the I.A.U. for the period January, 1949, through June, 1952, reveals that the average line width increases steadily with increasing central meridian distance of the flares. Furthermore, flares with exceptionally wide lines ( 4.0 A) are observed most often in flares 45 or more from the central meridian. The relation between effective line width and central intensity found by Ellison is explained as primarily a consequence of self-absorption. Finally, the existing observational evidence in favor of the Stark effect as an important cause of the line broadening is examined and found unconvincing. Title: Carbon Monoxide in the Sun. Authors: Goldberg, Leo; Müller, Edith A. Bibcode: 1953ApJ...118..397G Altcode: Nearly 300 llnes of carbon monoxide have been identified in the spectrum of the solar limb between 2.29 and 2.50 . The lines belong to the overtone bands 24), 31, 42, 33, , and 7-5. Analysis of the solar wave lengths has led to a new determination of the vibrational and rotational constants of the CO molecule. The measured absorption coefficients of Penner and Weber and the theoretical values of Scholz have been applied to the measured equivalent widths at the center of the disk. The resulting equivalent abundance of CO is 1.45 X t0' molecules per square centimeter above the photosphere, and the excitation temperature is 4300 K. It is shown from model-atmosphere calculations that solar Co is concentrated near the top of the photosphere and hence that the derived excitation temperature is consistent since it agrees with the boundary temperature. At present, it is not known whether the dissociation energy of CO is 9.6 or 11.1 e.v. If the lower value is correct, the solar-line intensities suggest that the boundary temperature is less than 4500 K. The exact value of the temperature depends on the choice of atomic abundances for 0 and C. The low intensities of the fundamental band lines of CO in the 4.6 region are explained as a consequence of (1) the high opacity of the solar atmosphere at long wave lengths, (2) the importance of stimulated emissions in the infrared, and (3) the small collisional line widths in the sun's outer layers.