Author name code: schleicher
ADS astronomy entries on 2022-09-14
author:Schleicher, H.
------------------------------------------------------------------------
Title: Proton acceleration in thermonuclear nova explosions revealed
by gamma rays
Authors: Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels,
A.; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres
de Almeida, U.; Barrio, J. A.; Batković, I.; Becerra González, J.;
Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti, A.;
Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch,
O.; Bökenkamp, H.; Bonnoli, G.; Bošnjak, Ž.; Busetto, G.; Carosi,
R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota,
S.; Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino,
S.; D'Amico, G.; D'Elia, V.; Da Vela, P.; Dazzi, F.; De Angelis, A.;
De Lotto, B.; Del Popolo, A.; Delfino, M.; Delgado, J.; Delgado Mendez,
C.; Depaoli, D.; Di Pierro, F.; Di Venere, L.; Do Souto Espiñeira, E.;
Prester, D. Dominis; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.;
Fallah Ramazani, V.; Fariña Alonso, L.; Fattorini, A.; Fonseca, M. V.;
Font, L.; Fruck, C.; Fukami, S.; Fukazawa, Y.; García López, R. J.;
Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano,
F.; Gliwny, P.; Godinović, N.; Green, J. G.; Green, D.; Hadasch, D.;
Hahn, A.; Hassan, T.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec, D.;
Hütten, M.; Inada, T.; Ishio, K.; Iwamura, Y.; Jiménez Martínez,
I.; Jormanainen, J.; Jouvin, L.; Kerszberg, D.; Kobayashi, Y.; Kubo,
H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.;
Linhoff, L.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya,
M.; López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.;
Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.;
Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez,
M.; Mas Aguilar, A.; Mazin, D.; Menchiari, S.; Mender, S.; Mićanović,
S.; Miceli, D.; Miener, T.; Miranda, J. M.; Mirzoyan, R.; Molina, E.;
Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Nakamori, T.;
Nava, L.; Neustroev, V.; Nievas Rosillo, M.; Nigro, C.; Nilsson, K.;
Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos,
J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes,
J. M.; Pavletić, L.; Peñil, P.; Persic, M.; Pihet, M.; Prada Moroni,
P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó,
M.; Rico, J.; Righi, C.; Rugliancich, A.; Sahakyan, N.; Saito, T.;
Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.; Schmidt,
K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon,
A.; Stamerra, A.; Strišković, J.; Strom, D.; Strzys, M.; Suda, Y.;
Surić, T.; Takahashi, M.; Takeishi, R.; Tavecchio, F.; Temnikov, P.;
Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach,
S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura,
S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.;
Wunderlich, C.; Yamamoto, T.; Zarić, D.; Ambrosino, F.; Cecconi,
M.; Catanzaro, G.; Ferrara, C.; Frasca, A.; Munari, M.; Giustolisi,
L.; Alonso-Santiago, J.; Giarrusso, M.; Munari, U.; Valisa, P.
Bibcode: 2022NatAs...6..689A
Altcode: 2022NatAs.tmp...83A; 2022NatAs.tmp...91A; 2022arXiv220207681M
Classical novae are cataclysmic binary star systems in
which the matter of a companion star is accreted on a white
dwarf1,2. Accumulation of hydrogen in a layer eventually
causes a thermonuclear explosion on the surface of the white
dwarf3, brightening the white dwarf to ~105 solar
luminosities and triggering ejection of the accumulated matter. Novae
provide the extreme conditions required to accelerate particles,
electrons or protons, to high energies. Here we present the detection
of gamma rays by the MAGIC telescopes from the 2021 outburst of RS
Ophiuchi, a recurrent nova with a red giant companion, which allowed us
to accurately characterize the emission from a nova in the 60 GeV to
250 GeV energy range. The theoretical interpretation of the combined
Fermi LAT and MAGIC data suggests that protons are accelerated to
hundreds of gigaelectronvolts in the nova shock. Such protons should
create bubbles of enhanced cosmic ray density, of the order of 10 pc,
from the recurrent novae.
Title: Searching for VHE gamma-ray emission associated with IceCube
neutrino alerts using FACT, H.E.S.S., MAGIC, and VERITAS
Authors: The Fact Collaboration; The H. E. S. S. Collaboration;
The Icecube Collaboration; The MAGIC Collaboration; The VERITAS
Collaboration; Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet
Engels, A.; Artero, M.; Asano, K.; Baack, D.; Babic, A.; Baquero,
A.; Barres de Almeida, U.; Barrio, J. A.; Batković, I.; Becerra
Gonzalez, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos,
M. I.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari,
C.; Biland, A.; Blanch, O.; Bökenkamp, H.; Bonnoli, G.; Bosnjak,
Z.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.;
Chilingarian, A.; Cikota, S.; Colak, S. M.; Colombo, E.; Contreras,
J. L.; Cortina, J.; Covino, S.; D'Amico, G.; D'Elia, V.; da Vela,
P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; Delfino, M.; Delgado,
J.; Delgado Mendez, C.; Depaoli, D.; di Pierro, F.; di Venere, L.;
Do Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner,
D.; Doro, M.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.;
Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; Fukazawa, Y.;
García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.;
Giglietto, N.; Giordano, F.; Gliwny, P.; Godinovic, N.; Green, D.;
Green, J. G.; Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.;
Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Ishio, K.; Iwamura,
Y.; Jiménez Martínez, I.; Jormanainen, J.; Jouvin, L.; Karjalainen,
M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.;
Lelas, D.; Leone, F.; Lindfors, E.; Linhoff, L.; Lombardi, S.; Longo,
F.; Lopez-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio,
S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev,
M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi,
L.; Mariotti, M.; Martinez, M.; Mazin, D.; Menchiari, S.; Mender, S.;
Mićanović, S.; Miceli, D.; Miener, T.; Miranda, J. M.; Mirzoyan,
R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti,
E.; Nakamori, T.; Nava, L.; Neustroev, V.; Nigro, C.; Nilsson, K.;
Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos,
J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes,
J. M.; Pavletić, L.; Peñil, P.; Persic, M.; Pihet, M.; Prada Moroni,
P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó,
M.; Rico, J.; Righi, C.; Rugliancich, A.; Sahakyan, N.; Saito, T.;
Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.; Schmidt,
K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczyńska, D.;
Spolon, A.; Stamerra, A.; Strišković, J.; Strom, D.; Strzys, M.;
Suda, Y.; Surić, T.; Takahashi, M.; Takeishi, R.; Tavecchio, F.;
Temnikov, P.; Terzic, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone,
A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.;
Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.;
Will, M.; Wunderlich, C.; Yamamoto, T.; Zarić, D.; Balbo, M.; Bretz,
T.; Buss, J.; Eisenberger, L.; Hildebrand, D.; Iotov, R.; Kalenski, A.;
Neise, D.; Noethe, M.; Paravac, A.; Sliusar, V.; Walter, R.; Abbasi,
R.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.;
Alispach, C. M.; Alves Junior, A. A.; Amin, N. M. B.; An, R.; Andeen,
K.; Anderson, T.; Anton, G.; Arguelles, C.; Ashida, Y.; Axani, S.;
Bai, X.; Balagopal v., A.; Barbano, A. M.; Barwick, S. W.; Bastian,
B.; Basu, V.; Baur, S.; Bay, R. C.; Beatty, J. J.; Becker, K. H.;
Becker Tjus, J.; Bellenghi, C.; Benzvi, S.; Berley, D.; Besson,
D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Boddenberg,
M.; Bontempo, F.; Borowka, J.; Boser, S.; Botner, O.; Bottcher, J.;
Bourbeau, E.; Bradascio, F.; Braun, J.; Bron, S.; Brostean-Kaiser,
J.; Browne, S. A.; Burgman, A.; Burley, R.; Busse, R.; Campana, M.;
Carnie-Bronca, E.; Chen, C.; Chirkin, D.; Choi, K.; Clark, B.; Clark,
K.; Classen, L.; Coleman, A.; Collin, G.; Conrad, J. M.; Coppin,
P.; Correa, P.; Cowen, D. F.; Cross, R.; Dappen, C.; Dave, P.; de
Clercq, C.; Delaunay, J.; Dembinski, H.; Deoskar, K.; De Ridder, S.;
Desai, A.; Desiati, P.; de Vries, K.; de Wasseige, G.; de With, M.;
Deyoung, T.; Dharani, S.; Diaz, A.; Diaz-Velez, J. C.; Dittmer, M.;
Dujmovic, H.; Dunkman, M.; Duvernois, M.; Dvorak, E.; Ehrhardt, T.;
Eller, P.; Engel, R.; Erpenbeck, H.; Evans, J.; Evenson, P. A.; Fan,
K. L.; Fazely, A. R.; Fiedlschuster, S.; Fienberg, A.; Filimonov,
K.; Finley, C.; Fischer, L.; Fox, D. B.; Franckowiak, A.; Friedman,
E.; Fritz, A.; Furst, P.; Gaisser, T. K.; Gallagher, J.; Ganster,
E.; Garcia, A.; Garrappa, S.; Gerhardt, L.; Ghadimi, A.; Glaser, C.;
Glauch, T.; Glusenkamp, T.; Goldschmidt, A.; Gonzalez, J.; Goswami,
S.; Grant, D.; Grégoire, T.; Griswold, S.; Gunduz, M.; Günther,
C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve, L.; Halzen, F.;
Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.; Haungs, A.;
Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.; Hettinger,
E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.; Hoffman, K.;
Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina, K.; Huang, F.;
Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.; Hussain, R.; in,
S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze, G.; Jeong, M.;
Jones, B.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.; Kappesser, D.;
Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.; Kellermann, M.;
Kelley, J. L.; Kheirandish, A.; Kin, K. I.; Kintscher, T.; Kiryluk,
J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas, T.; Kopke, L.;
Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.; Kovacevich, M.;
Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.; Lad, N.; Lagunas
Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber, F. H.; Lazar,
J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.; Lincetto, M.;
Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal, C. J.; Lu, L.;
Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma, W. Y.; Madsen,
J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.; Maruyama, R. H.;
Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.; Meagher, K.;
Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.; Mockler, D.;
Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab, R.; Nagai, R.;
Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen, H.; Nisa, M.;
Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Oehler, M.; Olivas,
A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.; Parker, G.;
Paudel, E. N.; Paul, L.; Perez de Los Heros, C.; Peters, L.; Philippen,
S.; Pieloth, D.; Pieper, S.; Pittermann, M.; Pizzuto, A.; Plum, M.;
Popovych, Y.; Porcelli, A.; Prado Rodriguez, M.; Price, P. B.; Pries,
B.; Przybylski, G.; Raab, C.; Raissi, A.; Rameez, M.; Rawlins, K.;
Rea, I. C.; Rehman, A.; Reimann, R.; Renzi, G.; Resconi, E.; Reusch,
S.; Richman, M.; Riedel, B.; Roberts, E.; Robertson, S.; Roellinghoff,
G.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.;
Safa, I.; Saffer, J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.;
Santander, M.; Sarkar, S.; Sarkar, S.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali, S.;
Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.;
Soldin, D.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska,
J.; Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer, A.;
Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.; Taboada,
I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein, F.; Tollefson,
K.; Tönnis, C.; Toscano, S.; Tosi, D.; Trettin, A.; Tselengidou, M.;
Tung, C.; Turcati, A.; Turcotte, R.; Turley, C.; Twagirayezu, J. P.;
Ty, B.; Unland Elorrieta, M.; Valtonen-Mattila, N.; Vandenbroucke,
J.; van Eijndhoven, N.; Vannerom, D.; van Santen, J.; Verpoest, S.;
Vraeghe, M.; Walck, C.; Watson, T.; Weaver, C.; Weigel, P.; Weindl,
A.; Weiss, M.; Weldert, J.; Wendt, C.; Werthebach, J.; Weyrauch, M.;
Whitehorn, N.; Wiebusch, C. H.; Williams, D.; Wolf, M.; Woschnagg,
K.; Wrede, G.; Wulff, J.; Xu, X.; Xu, Y.; Yanez, J. P.; Yoshida, S.;
Yu, S.; Yuan, T.; Zhang, Z.; Jin, W.; Abdalla, H.; Aharonian, F.;
Ait-Benkhali, F.; Anguener, O.; Arcaro, C.; Armand, C.; Armstrong, T.;
Ashkar, H.; Backes, M.; Baghmanyan, V.; Barbosa Martins, V.; Barnacka,
A.; Barnard, M.; Batzofin, R.; Becherini, Y.; Berge, D.; Bernlöhr, K.;
Bi, B.; Böttcher, M.; Boisson, C.; Bolmont, J.; de Bony, M.; Breuhaus,
M.; Brose, R.; Brun, F.; Bulik, T.; Bylund, T.; Cangemi, F.; Caroff,
S.; Casanova, S.; Catalano, J.; Chambery, P.; Chand, T. B.; Chen, A.;
Cotter, G.; Curlo, M.; Damascene Mbarubucyeye, J.; Davids, I. D.;
Davies, J.; Devin, J.; Djannati-Ataï, A.; Dmytriiev, A.; Donath,
A.; Doroshenko, V.; Dreyer, L.; Du Plessis, L.; Duffy, C.; Egberts,
K.; Einecke, S.; Emery, G.; Ernenwein, J. P.; Fegan, S.; Feijen, K.;
Fiasson, A.; Fichet de Clairfontaine, G.; Fontaine, G.; Frans, L.;
Fuessling, M.; Funk, S.; Gabici, S.; Gallant, Y.; Ghafourizade, S.;
Giavitto, G.; Giunti, L.; Glawion, D.; Glicenstein, J. F.; Grondin,
M. H.; Hattingh, S.; Haupt, M.; Hermann, G.; Hinton, J.; Hofmann, W.;
Hoischen, C.; Holch, T.; Holler, M.; Horns, D.; Huang, Z.; Huber, D.;
Hörbe, M.; Jamrozy, M.; Jankowsky, F.; Joshi, V.; Jung, I.; Kasai, E.;
Katarzynski, K.; Katz, U.; Khangulyan, D.; Khelifi, B.; Klepser, S.;
Kluzniak, W.; Komin, N.; Konno, R.; Kosack, K.; Kostunin, D.; Kreter,
M.; Kukec Mezek, G.; Kundu, A.; Lamanna, G.; Le Stum, S.; Lemiere, A.;
Lemoine-Goumard, M.; Lenain, J. P.; Leuschner, F.; Levy, C.; Lohse,
T.; Luashvili, A.; Lypova, I.; Mackey, J.; Majumdar, J.; Malyshev, D.;
Malyshev, D.; Marandon, V.; Marchegiani, P.; Marcowith, A.; Mares, A.;
Marti'I-Devesa, G.; Marx, R.; Maurin, G.; Meintjes, P.; Meyer, M.;
Mitchell, A.; Moderski, R.; Mohrmann, L.; Montanari, A.; Moore, C.;
Morris, P.; Moulin, E.; Muller, J.; Murach, T.; Nakashima, K.; Naurois
(de), M.; Nayerhoda, A.; Davids, H.; Niemiec, J.; Noel, A.; O'Brien,
P.; Oberholzer, L. L.; Ohm, S.; Olivera-Nieto, L.; Ona-Wilhelmi (de),
E.; Ostrowski, M.; Panny, S.; Panter, M.; Parsons, D.; Peron, G.;
Pita, S.; Poireau, V.; Prokhorov, D.; Prokoph, H.; Puehlhofer, G.;
Punch, M.; Quirrenbach, A.; Reichherzer, P.; Reimer, A.; Reimer, O.;
Remy, Q.; Renaud, M.; Reville, B.; Rieger, F.; Romoli, C.; Rowell,
G.; Rudak, B.; Rueda Ricarte, H.; Ruiz Velasco, E.; Sahakian, V.;
Sailer, S.; Salzmann, H.; Sanchez, D.; Santangelo, A.; Sasaki, M.;
Schaefer, J.; Schutte, H.; Schwanke, U.; Schüssler, F.; Senniappan,
M.; Seyffert, A.; Shapopi, J. N. S.; Shiningayamwe, K.; Simoni, R.;
Sinha, A.; Sol, H.; Spackman, H.; Specovius, A.; Spencer, S. T.;
Spir-Jacob, M.; Stawarz, L.; Steenkamp, R.; Stegmann, C.; Steinmassl,
S.; Steppa, C.; Sun, L.; Takahashi, T.; Tanaka, T.; Tavernier, T.;
Taylor, A.; Terrier, R.; Thiersen, H.; Thorpe-Morgan, C.; Tluczykont,
M.; Tomankova, L.; Tsirou, M.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.;
van der Walt, J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.;
Vasileiadis, G.; Veh, J.; Venter, C.; Vincent, P.; Vink, J.; Völk,
H. J.; Wagner, S.; Watson, J. J.; Werner, F.; White, R.; Wierzcholska,
A.; Wong, Y. W.; Yassin, H.; Yusafzai, A.; Zacharias, M.; Zanin, R.;
Zargaryan, D.; Zdziarski, A.; Zech, A.; Zhu, S.; Zmija, A.; Zouari,
S.; Żywucka, N.
Bibcode: 2022icrc.confE.960T
Altcode: 2022PoS...395E.960T; 2021arXiv210904350S
The realtime follow-up of neutrino events is a promising approach
to search for astrophysical neutrino sources. It has so far provided
compelling evidence for a neutrino point source: the flaring gamma-ray
blazar TXS 0506+056 observed in coincidence with the high-energy
neutrino IceCube-170922A detected by IceCube. The detection of
very-high-energy gamma rays (VHE, $\mathrm{E} > 100\,\mathrm{GeV}$)
from this source helped establish the coincidence and constrained the
modeling of the blazar emission at the time of the IceCube event. The
four major imaging atmospheric Cherenkov telescope arrays (IACTs)
- FACT, H.E.S.S., MAGIC, and VERITAS - operate an active follow-up
program of target-of-opportunity observations of neutrino alerts sent by
IceCube. This program has two main components. One are the observations
of known gamma-ray sources around which a cluster of candidate neutrino
events has been identified by IceCube (Gamma-ray Follow-Up, GFU). Second
one is the follow-up of single high-energy neutrino candidate events
of potential astrophysical origin such as IceCube-170922A. GFU has been
recently upgraded by IceCube in collaboration with the IACT groups. We
present here recent results from the IACT follow-up programs of IceCube
neutrino alerts and a description of the upgraded IceCube GFU system.
Title: MAGIC and H.E.S.S. detect VHE gamma rays from the blazar
OT081 for the first time: a deep multiwavelength study
Authors: Manganaro, M.; Seglar-Arroyo, M.; Becerra-González,
J.; Sanchez, D.; Cerruti, M.; Tavecchio, F.; Fallah-Ramazani,
V.; Agudo, I.; Ciprini, S.; Filippenko, A. V.; Esteban-Gutierrez,
A.; Hovatta, T.; Jermak, H.; Jorstad, S. G.; Kopatskaya, E. N.;
Larionov, V. M.; Larionova, L. V.; Lähteenmäki, A.; Marscher,
A.; Morozova, D. A.; Pahljina, M.; Tornikoski, M.; Troitskaya, Y.;
Troitsky, I.; Verrecchia, F.; Xiao, H. B.; Weaver, Z. R.; Zheng,
W.; The MAGIC Collaboration; The H. E. S. S. Collaboration; The
Fermi Large Area Telescope Collaboration; No Collaboration; Acciari,
V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Artero, M.;
Asano, K.; Baack, D.; Babic, A.; Baquero, A.; Barres de Almeida,
U.; Barrio, J. A.; Batković, I.; Becerra Gonzalez, J.; Bednarek,
W.; Bellizzi, L.; Bernardini, E.; Bernardos, M. I.; Berti, A.;
Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.;
Blanch, O.; Bökenkamp, H.; Bonnoli, G.; Bosnjak, Z.; Busetto, G.;
Carosi, R.; Ceribella, G.; Chai, Y.; Chilingarian, A.; Cikota, S.;
Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino,
S.; D'Amico, G.; D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis,
A.; de Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez, C.;
Depaoli, D.; di Pierro, F.; di Venere, L.; Do Souto Espiñeira, E.;
Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.;
Fallah Ramazani, V.; Fattorini, A.; Fonseca, M. V.; Font, L.; Fruck,
C.; Fukami, S.; Fukazawa, Y.; García López, R. J.; Garczarczyk,
M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny,
P.; Godinovic, N.; Green, D.; Green, J. G.; Hadasch, D.; Hahn, A.;
Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada,
T.; Ishio, K.; Iwamura, Y.; Jiménez Martínez, I.; Jormanainen,
J.; Jouvin, L.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo,
H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.;
Linhoff, L.; Lombardi, S.; Longo, F.; Lopez-Coto, R.; López-Moya,
M.; López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.;
Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.;
Mannheim, K.; Maraschi, L.; Mariotti, M.; Martinez, M.; Mazin, D.;
Menchiari, S.; Mender, S.; Mićanović, S.; Miceli, D.; Miener, T.;
Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende,
D.; Moreno, V.; Moretti, E.; Nakamori, T.; Nava, L.; Neustroev, V.;
Nigro, C.; Nilsson, K.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani,
Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque,
D.; Paoletti, R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Persic,
M.; Pihet, M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.;
Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.;
Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Saturni, F. G.;
Schleicher, B.; Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić,
I.; Sobczyńska, D.; Spolon, A.; Stamerra, A.; Strišković, J.; Strom,
D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Takeishi, R.;
Temnikov, P.; Terzic, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone,
A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.;
Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.;
Will, M.; Wunderlich, C.; Yamamoto, T.; Zarić, D.
Bibcode: 2022icrc.confE.815M
Altcode: 2022PoS...395E.815M
No abstract at ADS
Title: Combined searches for dark matter in dwarf spheroidal galaxies
observed with the MAGIC telescopes, including new data from Coma
Berenices and Draco
Authors: Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels,
A.; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres
de Almeida, U.; Barrio, J. A.; Batković, I.; Becerra González, J.;
Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti,
A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.;
Blanch, O.; Bökenkamp, H.; Bonnoli, G.; Bošnjak, Ž.; Busetto, G.;
Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.;
Cikota, S.; Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina,
J.; Covino, S.; D'Amico, G.; D'Elia, V.; da Vela, P.; Dazzi, F.; de
Angelis, A.; de Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez,
C.; Depaoli, D.; di Pierro, F.; di Venere, L.; Do Souto Espiñeira, E.;
Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.;
Fallah Ramazani, V.; Fattorini, A.; Fonseca, M. V.; Font, L.; Fruck,
C.; Fukami, S.; García López, R. J.; Garczarczyk, M.; Gasparyan,
S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović,
N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Heckmann, L.;
Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Ishio, K.;
Iwamura, Y.; Jiménez, I.; Jormanainen, J.; Jouvin, L.; Karjalainen,
M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.;
Lelas, D.; Leone, F.; Lindfors, E.; Linhoff, L.; Lombardi, S.; Longo,
F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio,
S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev,
M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi,
L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menchiari, S.; Mender, S.;
Mićanović, S.; Miceli, D.; Miener, T.; Miranda, J. M.; Mirzoyan,
R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti,
E.; Neustroev, V.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima,
K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.;
Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.;
Pavletić, L.; Peñil, P.; Persic, M.; Pihet, M.; Prada Moroni, P. G.;
Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó, M.; Rico,
J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.;
Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.; Schmidt,
K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon,
A.; Stamerra, A.; Strišković, J.; Strom, D.; Strzys, M.; Suda, Y.;
Surić, T.; Takahashi, M.; Takeishi, R.; Tavecchio, F.; Temnikov, P.;
Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach,
S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura,
S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.;
Wunderlich, C.; Zarić, D.; MAGIC Collaboration
Bibcode: 2022PDU....3500912A
Altcode: 2021arXiv211115009M
Milky Way dwarf spheroidal galaxies (dSphs) are among the best
candidates to search for signals of dark matter annihilation
with Imaging Atmospheric Cherenkov Telescopes, given their high
mass-to-light ratios and the fact that they are free of astrophysical
gamma-ray emitting sources. Since 2011, MAGIC has performed a multi-year
observation program in search for Weakly Interacting Massive Particles
(WIMPs) in dSphs. Results on the observations of Segue 1 and Ursa Major
II dSphs have already been published and include some of the most
stringent upper limits (ULs) on the velocity-averaged cross-section
«σann v » of WIMP annihilation from observations of
dSphs. In this work, we report on the analyses of 52.1 h of data of
Draco dSph and 49.5 h of Coma Berenices dSph observed with the MAGIC
telescopes in 2018 and in 2019 respectively. No hint of a signal has
been detected from either of these targets and new constraints on
the «σann v » of WIMP candidates have been derived. In
order to improve the sensitivity of the search and reduce the effect
of the systematic uncertainties due to the J-factor estimates, we have
combined the data of all dSphs observed with the MAGIC telescopes. Using
354.3 h of dSphs good quality data, 95% CL ULs on «σann
v » have been obtained for 9 annihilation channels. For most of the
channels, these results reach values of the order of 10-24
cm3/s at ∼ 1 TeV and are the most stringent limits obtained
with the MAGIC telescopes so far.
Title: Observation of the Gamma-Ray Binary HESS J0632+057 with the
H.E.S.S., MAGIC, and VERITAS Telescopes
Authors: Adams, C. B.; Benbow, W.; Brill, A.; Buckley, J. H.; Capasso,
M.; Chromey, A. J.; Errando, M.; Falcone, A.; A Farrell, K.; Feng,
Q.; Finley, J. P.; M Foote, G.; Fortson, L.; Furniss, A.; Gent,
A.; Gillanders, G. H.; Giuri, C.; Gueta, O.; Hanna, D.; Hassan, T.;
Hervet, O.; Holder, J.; Hona, B.; Humensky, T. B.; Jin, W.; Kaaret,
P.; Kertzman, M.; Kieda, D.; K Kleiner, T.; Krennrich, F.; Kumar,
S.; Lang, M. J.; Lundy, M.; Maier, G.; E McGrath, C.; Moriarty, P.;
Mukherjee, R.; Nieto, D.; Nievas-Rosillo, M.; O'Brien, S.; Ong, R. A.;
Otte, A. N.; Park, N.; Patel, S.; Pfrang, K.; Pichel, A.; Pohl, M.;
Prado, R. R.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.;
Roache, E.; Rovero, A. C.; Ryan, J. L.; Santander, M.; Schlenstedt,
S.; Sembroski, G. H.; Shang, R.; Tak, D.; Vassiliev, V. V.; Weinstein,
A.; Williams, D. A.; J Williamson, T.; J Williamson, T.; Acciari,
V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Artero, M.;
Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres de Almeida, U.;
Barrio, J. A.; Batković, I.; Becerra González, J.; Bednarek, W.;
Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti, A.; Besenrieder,
J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.;
Bökenkamp, H.; Bonnoli, G.; Bošnjak, Ž.; Busetto, G.; Carosi, R.;
Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.;
Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.;
D'Amico, G.; D'Elia, V.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De
Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.;
Di Pierro, F.; Di Venere, L.; Do Souto Espiñeira, E.; Dominis Prester,
D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Fallah Ramazani,
V.; Fattorini, A.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.;
Fukazawa, Y.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.;
Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.;
Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera,
J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Ishio, K.; Iwamura,
Y.; Jiménez Martínez, I.; Jormanainen, J.; Jouvin, L.; Karjalainen,
M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.;
Lelas, D.; Leone, F.; Lindfors, E.; Linhoff, L.; Lombardi, S.; Longo,
F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio,
S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev,
M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi,
L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menchiari, S.; Mender, S.;
Mićanović, S.; Miceli, D.; Miener, T.; Miranda, J. M.; Mirzoyan,
R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti,
E.; Nakamori, T.; Nava, L.; Neustroev, V.; Nigro, C.; Nilsson, K.;
Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos,
J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes,
J. M.; Pavletić, L.; Peñil, P.; Persic, M.; Pihet, M.; Prada Moroni,
P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó,
M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.;
Saito, T.; Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.;
Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska,
D.; Spolon, A.; Stamerra, A.; Strišković, J.; Strom, D.; Strzys,
M.; Suda, Y.; Surić, T.; Takahashi, M.; Takeishi, R.; Tavecchio,
F.; Temnikov, P.; Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.;
Tutone, A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez
Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.;
Vovk, I.; Will, M.; Wunderlich, C.; Yamamoto, T.; Zarić, D.; Zarić,
D.; Abdalla, H.; Aharonian, F.; Ait Benkhali, F.; Angüner, E. O.;
Arcaro, C.; Ashkar, H.; Backes, M.; Barbosa Martins, V.; Barnard,
M.; Batzofin, R.; Becherini, Y.; Berge, D.; Bernlöhr, K.; Bi, B.;
Böttcher, M.; Boisson, C.; Bolmont, J.; de Bony de Lavergne, M.;
Breuhaus, M.; Brose, R.; Brun, F.; Bulik, T.; Caroff, S.; Casanova, S.;
Chand, T.; Chen, A.; Cotter, G.; Damascenev Mbarubucyeye, J.; Devin,
J.; Djannati-Ataï, A.; Egberts, K.; Ernenwein, J. -P.; Fegan, S.;
Fiasson, A.; Fichet de Clairfontaine, G.; Fontaine, G.; Füßling, M.;
Funk, S.; Gabici, S.; Giavitto, G.; Glawion, D.; Glicenstein, J. F.;
Grondin, M. -H.; Hinton, J. A.; Hofmann, W.; Holch, T. L.; Holler,
M.; Horns, D.; Huang, Zhiqiu; Jamrozy, M.; Jankowsky, F.; Joshi, V.;
Jung-Richardt, I.; Kasai, E.; Katarzyński, K.; Khélifi, B.; Komin,
Nu.; Kosack, K.; Kostunin, D.; Le Stum, S.; Lemière, A.; Lenain,
J. -P.; Leuschner, F.; Levy, C.; Lohse, T.; Luashvili, A.; Lypova,
I.; Mackey, J.; Majumdar, J.; Malyshev, D.; Marandon, V.; Marchegiani,
P.; Marcowith, A.; Martí-Devesa, G.; Marx, R.; Maurin, G.; Meintjes,
P. J.; Mitchell, A.; Moderski, R.; Mohrmann, L.; Montanari, A.; Moulin,
E.; Muller, J.; Murach, T.; de Naurois, M.; Nayerhoda, A.; Niemiec,
J.; Priyana Noel, A.; O'Brien, P.; Ohm, S.; Olivera-Nieto, L.; de Ona
Wilhelmi, E.; Ostrowski, M.; Panny, S.; Panter, M.; Parsons, R. D.;
Peron, G.; Poireau, V.; Prokhorov, D. A.; Prokoph, H.; Pühlhofer,
G.; Punch, M.; Quirrenbach, A.; Reichherzer, P.; Reimer, A.; Reimer,
O.; Renaud, M.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rueda
Ricarte, H.; Ruiz-Velasco, E.; Sahakian, V.; Sailer, S.; Salzmann, H.;
Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schutte, H. M.; Schwanke,
U.; Schüssler, F.; Senniappan, M.; Shapopi, J. N. S.; Simoni, R.;
Sol, H.; Specovius, A.; Spencer, S.; Steenkamp, R.; Steinmassl, S.;
Sun, L.; Takahashi, T.; Tanaka, T.; Terrier, R.; Tsuji, N.; Uchiyama,
Y.; van Eldik, C.; van Soelen, B.; Veh, J.; Venter, C.; Vink, J.;
Wagner, S. J.; White, R.; Wierzcholska, A.; Wun Wong, Yu; Zacharias,
M.; Zargaryan, D.; Zdziarski, A. A.; Zech, A.; Zhu, S. J.; Zouari,
S.; Żywucka, N.; Żywucka, N.; Moritani, Y.; Torres, D. F.
Bibcode: 2021ApJ...923..241A
Altcode: 2021arXiv210911894A
The results of gamma-ray observations of the binary system HESS
J0632 + 057 collected during 450 hr over 15 yr, between 2004 and
2019, are presented. Data taken with the atmospheric Cherenkov
telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV
were used together with observations at X-ray energies obtained
with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some
of these observations were accompanied by measurements of the Hα
emission line. A significant detection of the modulation of the very
high-energy gamma-ray fluxes with a period of 316.7 ± 4.4 days is
reported, consistent with the period of 317.3 ± 0.7 days obtained
with a refined analysis of X-ray data. The analysis of data from four
orbital cycles with dense observational coverage reveals short-timescale
variability, with flux-decay timescales of less than 20 days at very
high energies. Flux variations observed over a timescale of several
years indicate orbit-to-orbit variability. The analysis confirms the
previously reported correlation of X-ray and gamma-ray emission from
the system at very high significance, but cannot find any correlation
of optical Hα parameters with fluxes at X-ray or gamma-ray energies
in simultaneous observations. The key finding is that the emission of
HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly
variable on different timescales. The ratio of gamma-ray to X-ray
flux shows the equality or even dominance of the gamma-ray energy
range. This wealth of new data is interpreted taking into account the
insufficient knowledge of the ephemeris of the system, and discussed
in the context of results reported on other gamma-ray binary systems.
Title: First detection of VHE gamma-ray emission from TXS 1515-273,
study of its X-ray variability and spectral energy distribution
Authors: Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels,
A.; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; Barres
de Almeida, U.; Barrio, J. A.; Batković, I.; Becerra González, J.;
Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti,
A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.;
Blanch, O.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.;
Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colak, S. M.;
Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.;
D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.;
Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; Pierro,
F. Di; Venere, L. Di; Do Souto Espiñeira, E.; Dominis Prester, D.;
Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Fallah Ramazani,
V.; Fattorini, A.; Ferrara, G.; Fonseca, M. V.; Font, L.; Fruck,
C.; Fukami, S.; García López, R. J.; Garczarczyk, M.; Gasparyan,
S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović,
N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Heckmann, L.;
Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Inoue,
S.; Ishio, K.; Iwamura, Y.; Jiménez, I.; Jormanainen, J.; Jouvin,
L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.;
Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors,
E.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.;
López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.;
Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.;
Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez,
M.; Mazin, D.; Menchiari, S.; Mender, S.; Mićanović, S.; Miceli,
D.; Miener, T.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.;
Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Neustroev, V.;
Nigro, C.; Nilsson, K.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani,
Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque,
D.; Paoletti, R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes,
C.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.;
Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich,
A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.;
Saturni, F. G.; Schleicher, B.; Schmidt, K.; Schweizer, T.; Sitarek,
J.; Šnidarić, I.; Sobczynska, D.; Spolon, A.; Stamerra, A.; Strom,
D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.;
Temnikov, P.; Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone,
A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.;
Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.;
Will, M.; Wunderlich, C.; Zarić, D.; Bissaldi, E.; Bonnoli, G.;
Cutini, S.; D'Ammando, F.; Nabizadeh, A.; Marchini, A.; Orienti, M.;
MAGIC Collaboration
Bibcode: 2021MNRAS.507.1528A
Altcode: 2021arXiv210709413M; 2021MNRAS.tmp.1875A; 2021MNRAS.507.1528M
We report here on the first multiwavelength (MWL) campaign on the
blazar TXS 1515-273, undertaken in 2019 and extending from radio to
very-high-energy gamma-rays (VHE). Up until now, this blazar had not
been the subject of any detailed MWL observations. It has a rather
hard photon index at GeV energies and was considered a candidate
extreme high-synchrotron-peaked source. MAGIC observations resulted
in the first-time detection of the source in VHE with a statistical
significance of 7.6σ. The average integral VHE flux of the source
is 6 ± 1 per cent of the Crab nebula flux above 400 GeV. X-ray
coverage was provided by Swift-XRT, XMM-Newton, and NuSTAR. The long
continuous X-ray observations were separated by ~9 h, both showing
clear hour scale flares. In the XMM-Newton data, both the rise and
decay time-scales are longer in the soft X-ray than in the hard X-ray
band, indicating the presence of a particle cooling regime. The X-ray
variability time-scales were used to constrain the size of the emission
region and the strength of the magnetic field. The data allowed us to
determine the synchrotron peak frequency and classify the source as a
flaring high, but not extreme synchrotron-peaked object. Considering the
constraints and variability patterns from the X-ray data, we model the
broad-band spectral energy distribution. We applied a simple one-zone
model, which could not reproduce the radio emission and the shape of
the optical emission, and a two-component leptonic model with two
interacting components, enabling us to reproduce the emission from
radio to VHE band.
Title: Modelling H2 and its effects on star formation
using a joint implementation of GADGET-3 and KROME
Authors: Sillero, Emanuel; Tissera, Patricia B.; Lambas, Diego G.;
Bovino, Stefano; Schleicher, Dominik R.; Grassi, Tommaso; Bruzual,
Gustavo; Charlot, Stéphane
Bibcode: 2021MNRAS.504.2325S
Altcode: 2021MNRAS.tmp.1021S; 2021arXiv210404357S
We present P-GADGET3-K, an updated version of GADGET-3, that
incorporates the chemistry package KROME. P-GADGET3-K follows
the hydrodynamical and chemical evolution of cosmic structures,
incorporating the chemistry and cooling of H2 and metal
cooling in non-equilibrium. We performed different runs of the same ICs
to assess the impact of various physical parameters and prescriptions,
namely gas metallicity, molecular hydrogen formation on dust, star
formation recipes including or not H2 dependence, and the
effects of numerical resolution. We find that the characteristics
of the simulated systems, both globally and at kpc-scales, are in
good agreement with several observable properties of molecular gas in
star-forming galaxies. The surface density profiles of star formation
rate (SFR) and H2 are found to vary with the clumping factor
and resolution. In agreement with previous results, the chemical
enrichment of the gas component is found to be a key ingredient to
model the formation and distribution of H2 as a function
of gas density and temperature. A star formation algorithm that takes
into account the H2 fraction together with a treatment for
the local stellar radiation field improves the agreement with observed
H2 abundances over a wide range of gas densities and with
the molecular Kennicutt-Schmidt law, implying a more realistic modelling
of the star formation process.
Title: H.E.S.S. and MAGIC observations of a sudden cessation of a
very-high-energy γ-ray flare in PKS 1510−089 in May 2016
Authors: H. E. S. S. Collaboration; Abdalla, H.; Adam, R.; Aharonian,
F.; Ait Benkhali, F.; Angüner, E. O.; Arcaro, C.; Armand, C.;
Armstrong, T.; Ashkar, H.; Backes, M.; Baghmanyan, V.; Barbosa Martins,
V.; Barnacka, A.; Barnard, M.; Becherini, Y.; Berge, D.; Bernlöhr,
K.; Bi, B.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; de
Bony de Lavergne, M.; Bregeon, J.; Breuhaus, M.; Brun, F.; Brun, P.;
Bryan, M.; Büchele, M.; Bulik, T.; Bylund, T.; Caroff, S.; Carosi, A.;
Casanova, S.; Chand, T.; Chandra, S.; Chen, A.; Cotter, G.; Curyło,
M.; Damascene Mbarubucyeye, J.; Davids, I. D.; Davies, J.; Deil, C.;
Devin, J.; Dewilt, P.; Dirson, L.; Djannati-Ataï, A.; Dmytriiev,
A.; Donath, A.; Doroshenko, V.; Dyks, J.; Egberts, K.; Eichhorn, F.;
Einecke, S.; Emery, G.; Ernenwein, J. -P.; Feijen, K.; Fegan, S.;
Fiasson, A.; Fichet de Clairfontaine, G.; Filipovic, M.; Fontaine,
G.; Funk, S.; Füßling, M.; Gabici, S.; Gallant, Y. A.; Giavitto, G.;
Giunti, L.; Glawion, D.; Glicenstein, J. F.; Gottschall, D.; Grondin,
M. -H.; Hahn, J.; Haupt, M.; Hermann, G.; Hinton, J. A.; Hofmann, W.;
Hoischen, C.; Holch, T. L.; Holler, M.; Hörbe, M.; Horns, D.; Huber,
D.; Jamrozy, M.; Jankowsky, D.; Jankowsky, F.; Jardin-Blicq, A.; Joshi,
V.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katz,
U.; Khangulyan, D.; Khélifi, B.; Klepser, S.; Kluźniak, W.; Komin,
Nu.; Konno, R.; Kosack, K.; Kostunin, D.; Kreter, M.; Lamanna, G.;
Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P.; Levy, C.; Lohse,
T.; Lypova, I.; Mackey, J.; Majumdar, J.; Malyshev, D.; Malyshev, D.;
Marandon, V.; Marchegiani, P.; Marcowith, A.; Mares, A.; Martí-Devesa,
G.; Marx, R.; Maurin, G.; Meintjes, P. J.; Meyer, M.; Mitchell,
A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Montanari, A.;
Moore, C.; Morris, P.; Moulin, E.; Muller, J.; Murach, T.; Nakashima,
K.; Nayerhoda, A.; de Naurois, M.; Ndiyavala, H.; Niederwanger, F.;
Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; Olivera-Nieto,
L.; de Ona Wilhelmi, E.; Ostrowski, M.; Panter, M.; Panny, S.; Parsons,
R. D.; Peron, G.; Peyaud, B.; Piel, Q.; Pita, S.; Poireau, V.; Priyana
Noel, A.; Prokhorov, D. A.; Prokoph, H.; Pühlhofer, G.; Punch, M.;
Quirrenbach, A.; Raab, S.; Rauth, R.; Reichherzer, P.; Reimer, A.;
Reimer, O.; Remy, Q.; Renaud, M.; Rieger, F.; Rinchiuso, L.; Romoli,
C.; Rowell, G.; Rudak, B.; Ruiz-Velasco, E.; Sahakian, V.; Sailer, S.;
Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Scalici, M.; Schüssler,
F.; Schutte, H. M.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.;
Senniappan, M.; Seyffert, A. S.; Shafi, N.; Shiningayamwe, K.; Simoni,
R.; Sinha, A.; Sol, H.; Specovius, A.; Spencer, S.; Spir-Jacob, M.;
Stawarz, Ł.; Sun, L.; Steenkamp, R.; Stegmann, C.; Steinmassl, S.;
Steppa, C.; Takahashi, T.; Tavernier, T.; Taylor, A. M.; Terrier, R.;
Tiziani, D.; Tluczykont, M.; Tomankova, L.; Trichard, C.; Tsirou,
M.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.;
van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter,
C.; Vincent, P.; Vink, J.; Völk, H. J.; Vuillaume, T.; Wadiasingh,
Z.; Wagner, S. J.; Watson, J.; Werner, F.; White, R.; Wierzcholska,
A.; Wong, Yu. W.; Yusafzai, A.; Zacharias, M.; Zanin, R.; Zargaryan,
D.; Zdziarski, A. A.; Zech, A.; Zhu, S. J.; Zorn, J.; Zouari, S.;
Żywucka, N.; MAGIC Collaboration; Acciari, V. A.; Ansoldi, S.;
Antonelli, L. A.; Arbet Engels, A.; Asano, K.; Baack, D.; Babić, A.;
Baquero, A.; Barres de Almeida, U.; Barrio, J. A.; Becerra González,
J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Berti, A.; Besenrieder,
J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bonnoli,
G.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti,
M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colak, S. M.; Colin, U.;
Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.;
D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.;
Delfino, M.; Delgado, J.; Depaoli, D.; di Pierro, F.; di Venere, L.;
Do Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.;
Doro, M.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.; Ferrara,
G.; Foffano, L.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.;
García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.;
Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, D.;
Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec,
D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jouvin,
L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo,
H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.;
Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas,
A.; Loporchio, S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar,
P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim,
K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Mender, S.;
Mićanović, S.; Miceli, D.; Miener, T.; Minev, M.; Miranda, J. M.;
Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.;
Moretti, E.; Munar-Adrover, P.; Neustroev, V.; Nigro, C.; Nilsson,
K.; Ninci, D.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.;
Oka, T.; Otero-Santos, J.; Palatiello, M.; Paneque, D.; Paoletti,
R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes, C.; Persic,
M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.;
Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.;
Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Schleicher, B.;
Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska,
D.; Spolon, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić,
T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima,
M.; Torres-Albà, N.; Tosti, L.; Truzzi, S.; van Scherpenberg, J.;
Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito,
C. F.; Vitale, V.; Vovk, I.; Will, M.; Zarić, D.; Jorstad, S. G.;
Marscher, A. P.; Boccardi, B.; Casadio, C.; Hodgson, J.; Kim, J. -Y.;
Krichbaum, T. P.; Lähteenmäki, A.; Tornikoski, M.; Traianou, E.;
Weaver, Z. R.
Bibcode: 2021A&A...648A..23H
Altcode: 2020arXiv201210254H
The flat spectrum radio quasar (FSRQ) PKS 1510−089 is known for its
complex multiwavelength behaviour and it is one of only a few FSRQs
detected in very-high-energy (VHE, E > 100 GeV) γ rays. The VHE
γ-ray observations with H.E.S.S. and MAGIC in late May and early
June 2016 resulted in the detection of an unprecedented flare, which
revealed, for the first time, VHE γ-ray intranight variability for
this source. While a common variability timescale of 1.5 h has been
found, there is a significant deviation near the end of the flare, with
a timescale of ∼20 min marking the cessation of the event. The peak
flux is nearly two orders of magnitude above the low-level emission. For
the first time, a curvature was detected in the VHE γ-ray spectrum
of PKS 1510-089, which can be fully explained by the absorption
on the part of the extragalactic background light. Optical R-band
observations with ATOM revealed a counterpart of the γ-ray flare,
even though the detailed flux evolution differs from the VHE γ-ray
light curve. Interestingly, a steep flux decrease was observed at the
same time as the cessation of the VHE γ-ray flare. In the high-energy
(HE, E > 100 MeV) γ-ray band, only a moderate flux increase was
observed with Fermi-LAT, while the HE γ-ray spectrum significantly
hardens up to a photon index of 1.6. A search for broad-line region
(BLR) absorption features in the γ-ray spectrum indicates that the
emission region is located outside of the BLR. Radio very-long-baseline
interferometry observations reveal a fast-moving knot interacting with
a standing jet feature around the time of the flare. As the standing
feature is located ∼50 pc from the black hole, the emission region
of the flare may have been located at a significant distance from the
black hole. If this is indeed a true correlation, the VHE γ rays must
have been produced far down in the jet, where turbulent plasma crosses
a standing shock.
Title: Constructing a Probabilistic Seismic Hazard Analysis Framework
for the Moon
Authors: Banks, Maria; Watters, Thomas; Weber, Renee; Schleicher,
Lisa S.; Bensi, Michelle; Schmerr, Nicholas
Bibcode: 2021cosp...43E.358B
Altcode:
Introduction: Global coverage with high resolution images and
altimetry data from the Lunar Reconnaissance Orbiter (LRO) spacecraft
have enabled detailed mapping of both contractional and extensional
tectonic features on the Moon including wrinkle ridges, graben, and
over 3500 young lobate scarps [e.g., 1-3]. Lobate scarps (thrust fault
scarps) in particular are widespread across the lunar surface [1-3]
and are believed to have been active within the past $\sim$400 Ma,
with some potentially still currently active [1, 4, 5]. The locations
of the young fault scarps can now be combined with newly developed
seismic ground motion shakemaps [1] and data from the Apollo-era seismic
network on distributed seismicity and the nature of the near-subsurface
structure [6-8]. These data and information collectively offer the
components needed to develop a preliminary probabilistic seismic
hazard analysis (PSHA) for the Moon. We explore the application of
PSHA methods utilized in the nuclear industry [e.g., 9-11] and more
broadly. These methods may provide a useful resource for evaluating
seismic hazards on the lunar surface, both globally and at high priority
landing sites and future locations of extended surface operations or
permanent structures (for example near permanently shadowed regions
(PSRs)). Such a hazard evaluation is potentially applicable to any
terrestrial body with evidence of tectonic activity and is essential
to support the future design and construction of structures, systems,
and components [12], and to aid in the development of future seismic
monitoring networks. Methods: Traditional PSHA calculations involve
integrating information regarding the location and magnitude of possible
seismic sources and their estimated frequencies of occurrence (seismic
source model), estimates of ground motion attenuation (ground motion
model), and the effect of the near-surface on the amplification of
ground motions (site response model), to estimate the probability
and severity of expected ground motion at a site of interest [9-11],
and regional effects. Results of a PSHA are typically presented as
a seismic hazard curve, which presents a measure of ground motion
severity (e.g., peak ground acceleration) on one axis and the (annual)
frequency of exceedance on the other axis (see [13-14]). The results of
this analysis will demonstrate the development of preliminary hazard
curves, which can be used to estimate seismic hazards. This analysis
will also help target areas where additional orbital and/or in-situ
data may be needed to develop a more robust PSHA for design purposes
for future exploration. Acknowledgments: We thank the LRO science teams,
engineers, and technical support personnel. Support provided by the NASA
Solar System Exploration Research Virtual Institute (SSERVI) Cooperative
Agreement NNH16ZDA001N, TREX team, and the SSERVI Grant 80NSSC19M0216,
GEODES team. References: [1] Watters et al. (2019) Nature Geoscience,
12, 411-417 [2] Watters, T.R., et al. (2010) Science, 329, 936-940;
[3] Watters, T.R., et al. (2015) Geology, 43, 851-854; [4] van der
Bogert C. H. et al. (2018) Icarus, 306, 225-242. [5] Clark J. D. et
al. (2015) LPSC XLVI, Abstract #1730. [6] Nakamura, Y. et al. (1979)
Proc. Tenth Lunar Sci. Conf., 2299-2309 [7] Nakamura, Y. et al. (1981)
Institute for Geophysics, Univ. of Texas, 188; [8] Nakamura, Y. (1982)
J. Geophys. Res, 87; [9] American National Standards Institute (ANSI)
/ American Nuclear Society (ANS) Standard 2.29, Probabilistic Seismic
Hazard Analysis (2008); [10] Nuclear Regulatory Commission, Regulatory
Guide 1.208 (2007); [11] Nuclear Regulatory Commission NUREG-1350,
Volume 27 (2016); [12] Justh, H. et al. (2016) Natural Environments
Definition for Design. NASA/TM—2016-218229. [13] Nuclear Regulatory
Commission NUREG-2213 (2018); [14] Baker, J. (2013), Probablistic
Seismic Hazard Analysis, White Paper Version 2.0.1, 79 pages.
Title: Detection of the Geminga pulsar with MAGIC hints at a power-law
tail emission beyond 15 GeV
Authors: MAGIC Collaboration; Acciari, V. A.; Ansoldi, S.; Antonelli,
L. A.; Arbet Engels, A.; Asano, K.; Baack, D.; Babić, A.; Baquero,
A.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.;
Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti,
A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.;
Blanch, O.; Bonnoli, G.; Bošnjak, Ž.; Busetto, G.; Carosi, R.;
Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.;
Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.;
D'Amico, G.; D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis, A.; de
Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.;
di Girolamo, T.; di Pierro, F.; di Venere, L.; Do Souto Espiñeira,
E.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser,
D.; Fallah Ramazani, V.; Fattorini, A.; Ferrara, G.; Foffano, L.;
Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; García López, R. J.;
Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano,
F.; Gliwny, P.; Godinović, N.; Green, J. G.; Green, D.; Hadasch, D.;
Hahn, A.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten,
M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jormanainen, J.;
Jouvin, L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi,
Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.;
Lindfors, E.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya,
M.; López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.;
Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.;
Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez,
M.; Mazin, D.; Mender, S.; Mićanović, S.; Miceli, D.; Miener, T.;
Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.;
Morcuende, D.; Moreno, V.; Moretti, E.; Munar-Adrover, P.; Neustroev,
V.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nozaki,
S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.; Palatiello, M.; Paneque,
D.; Paoletti, R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes,
C.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.;
Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich,
A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.;
Saturni, F. G.; Schleicher, B.; Schmidt, K.; Schweizer, T.; Sitarek,
J.; Šnidarić, I.; Sobczynska, D.; Spolon, A.; Stamerra, A.; Strom,
D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.;
Temnikov, P.; Terzić, T.; Teshima, M.; Torres-Albà, N.; Tosti,
L.; Truzzi, S.; Tutone, A.; van Scherpenberg, J.; Vanzo, G.; Vazquez
Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.;
Vovk, I.; Will, M.; Zarić, D.; Hirotani, K.; Saz Parkinson, P. M.
Bibcode: 2020A&A...643L..14M
Altcode: 2020arXiv201110412M
We report the detection of pulsed gamma-ray emission from the
Geminga pulsar (PSR J0633+1746) between 15 GeV and 75 GeV. This is
the first time a middle-aged pulsar has been detected up to these
energies. Observations were carried out with the MAGIC telescopes
between 2017 and 2019 using the low-energy threshold Sum-Trigger-II
system. After quality selection cuts, ∼80 h of observational data
were used for this analysis. To compare with the emission at lower
energies below the sensitivity range of MAGIC, 11 years of Fermi-LAT
data above 100 MeV were also analysed. From the two pulses per rotation
seen by Fermi-LAT, only the second one, P2, is detected in the MAGIC
energy range, with a significance of 6.3σ. The spectrum measured
by MAGIC is well-represented by a simple power law of spectral index
Γ = 5.62 ± 0.54, which smoothly extends the Fermi-LAT spectrum. A
joint fit to MAGIC and Fermi-LAT data rules out the existence of a
sub-exponential cut-off in the combined energy range at the 3.6σ
significance level. The power-law tail emission detected by MAGIC
is interpreted as the transition from curvature radiation to Inverse
Compton Scattering of particles accelerated in the northern outer gap.
Title: Study of the GeV to TeV morphology of the $\gamma$-Cygni SNR
(G78.2+2.1) with MAGIC and Fermi-LAT
Authors: MAGIC Collaboration; Acciari, V. A.; Ansoldi, S.; Antonelli,
L. A.; Arbet Engels, A.; Baack, D.; Babić, A.; Banerjee, B.; Barres
de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek,
W.; Bellizzi, L.; Bernardini, E.; Berti, A.; Besenrieder, J.;
Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bonnoli,
G.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti,
M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colak, S. M.; Colin, U.;
Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Elia, V.;
Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Delfino, M.;
Delgado, J.; Depaoli, D.; Di Pierro, F.; Di Venere, L.; Do Souto
Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro,
M.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.; Ferrara, G.;
Foffano, L.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; García
López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto,
N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, D.; Hadasch, D.;
Hahn, A.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada,
T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jouvin, L.; Kajiwara, Y.;
Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida,
J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.;
Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Loporchio,
S.; Machado de Oliveira Fraga, B.; Masuda, S.; Maggio, C.; Majumdar,
P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim,
K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Mender, S.;
Mićanović, S.; Miceli, D.; Miener, T.; Minev, M.; Miranda, J. M.;
Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.;
Moretti, E.; Munar-Adrover, P.; Neustroev, V.; Nigro, C.; Nilsson, K.;
Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Nozaki, S.; Ohtani,
Y.; Oka, T.; Otero-Santos, J.; Palatiello, M.; Paneque, D.; Paoletti,
R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Peresano, M.; Persic,
M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Rhode, W.; Ribó,
M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.;
Saito, T.; Sakurai, S.; Satalecka, K.; Schleicher, B.; Schmidt, K.;
Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon,
A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.;
Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima,
M.; Torres-Albà, N.; Tosti, L.; van Scherpenberg, J.; Vanzo, G.;
Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito, C. F.;
Vitale, V.; Vovk, I.; Will, M.; Zarić, D.; authors, External; :;
Celli, S.; Morlino, G.
Bibcode: 2020arXiv201015854M
Altcode:
Context. Diffusive shock acceleration (DSA) is the most promising
mechanism to accelerate Galactic cosmic rays (CRs) in the shocks
of supernova remnants (SNRs). The turbulence upstream is supposedly
generated by the CRs, but this process is not well understood. The
dominant mechanism may depend on the evolutionary state of the shock
and can be studied via the CRs escaping upstream into the interstellar
medium (ISM). Aims. Previous observations of the $\gamma$-Cygni SNR
showed a difference in morphology between GeV and TeV energies. Since
this SNR has the right age and is at the evolutionary stage for a
significant fraction of CRs to escape, we aim to understand $\gamma$-ray
emission in the vicinity of the $\gamma$-Cygni SNR. Methods. We
observed the region of the $\gamma$-Cygni SNR with the MAGIC Imaging
Atmospheric Cherenkov telescopes between May 2015 and September
2017 recording 87 h of good-quality data. Additionally we analysed
Fermi-LAT data to study the energy dependence of the morphology
as well as the energy spectrum in the GeV to TeV range. The energy
spectra and morphology were compared against theoretical predictions,
which include a detailed derivation of the CR escape process and their
$\gamma$-ray generation. Results. The MAGIC and Fermi-LAT data allowed
us to identify three emission regions, which can be associated with the
SNR and dominate at different energies. Our hadronic emission model
accounts well for the morphology and energy spectrum of all source
components. It constrains the time-dependence of the maximum energy of
the CRs at the shock, the time-dependence of the level of turbulence,
and the diffusion coefficient immediately outside the SNR shock. While
in agreement with the standard picture of DSA, the time-dependence
of the maximum energy was found to be steeper than predicted and the
level of turbulence was found to change over the lifetime of the SNR.
Title: Studying the nature of the unidentified gamma-ray source HESS
J1841-055 with the MAGIC telescopes
Authors: MAGIC Collaboration; Acciari, V. A.; Ansoldi, S.; Antonelli,
L. A.; Arbet Engels, A.; Asano, K.; Baack, D.; Babić, A.; Banerjee,
B.; Baquero, A.; Barres de Almeida, U.; Barrio, J. A.; Becerra
González, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos,
M.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.;
Biland, A.; Blanch, O.; Bonnoli, G.; Bošnjak, Ž.; Busetto, G.;
Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.;
Cikota, S.; Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina,
J.; Covino, S.; D'Amico, G.; D'Elia, V.; da Vela, P.; Dazzi, F.; de
Angelis, A.; de Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez,
C.; Depaoli, D.; di Girolamo, T.; di Pierro, F.; di Venere, L.; Do
Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.;
Doro, M.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.; Ferrara,
G.; Foffano, L.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.;
García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.;
Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, D.;
Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec,
D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jouvin,
L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo,
H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.;
Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas,
A.; Loporchio, S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar,
P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim,
K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Mender, S.;
Mićanović, S.; Miceli, D.; Miener, T.; Minev, M.; Miranda, J. M.;
Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.;
Moretti, E.; Munar-Adrover, P.; Neustroev, V.; Nigro, C.; Nilsson,
K.; Ninci, D.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.;
Oka, T.; Otero-Santos, J.; Palatiello, M.; Paneque, D.; Paoletti,
R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes, C.; Persic,
M.; Prada Moroni, P. G.; Prandini, E.; Priyadarshi, C.; Puljak, I.;
Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.;
Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Schleicher, B.;
Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska,
D.; Spolon, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić,
T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima,
M.; Torres-Albà, N.; Tosti, L.; Truzzi, S.; van Scherpenberg, J.;
Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito,
C. F.; Vitale, V.; Vovk, I.; Will, M.; Zarić, D.
Bibcode: 2020MNRAS.497.3734M
Altcode: 2020arXiv200709321M; 2020MNRAS.497.3734A; 2020MNRAS.tmp.2246A
We investigate the physical nature and origin of the gamma-ray
emission from the extended source HESS J1841-055 observed at TeV
and GeV energies. We observed HESS J1841-055 at TeV energies for a
total effective time of 43 h with the MAGIC telescopes, in 2012 and
2013. Additionally, we analysed the GeV counterpart making use of about
10 yr of Fermi-LAT data. Using both Fermi-LAT and MAGIC, we study
both the spectral and energy-dependent morphology of the source for
almost four decades of energy. The origin of the gamma-ray emission
from this region is investigated using multiwaveband information on
sources present in this region, suggested to be associated with this
unidentified gamma-ray source. We find that the extended emission at
GeV-TeV energies is best described by more than one source model. We
also perform the first energy-dependent analysis of the HESS J1841-055
region at GeV-TeV. We find that the emission at lower energies comes
from a diffuse or extended component, while the major contribution
of gamma rays above 1 TeV arises from the southern part of the
source. Moreover, we find that a significant curvature is present
in the combined observed spectrum of MAGIC and Fermi-LAT. The first
multiwavelength spectral energy distribution of this unidentified source
shows that the emission at GeV-TeV energies can be well explained
with both leptonic and hadronic models. For the leptonic scenario,
bremsstrahlung is the dominant emission compared to inverse Compton. On
the other hand, for the hadronic model, gamma-ray resulting from
the decay of neutral pions (π0) can explain the observed
spectrum. The presence of dense molecular clouds overlapping with HESS
J1841-055 makes both bremsstrahlung and π0-decay processes
the dominant emission mechanisms for the source.
Title: Synthetic observations of deuterated molecules in massive
prestellar cores
Authors: Zamponi F., Joaquin; Giannetti, Andrea; Bovino, Stefano;
Sabatini, Giovanni; Schleicher, Dominik R. G.; Körtgen, Bastian;
Reissl, Stefan; Wolf, Sebastian
Bibcode: 2020arXiv200900407Z
Altcode:
Young massive stars are usually found embedded in dense massive
molecular clumps and are known for being highly obscured and
distant. During their formation process, deuteration is regarded as
a potentially good indicator of the very early formation stages. In
this work, we test the observability of the ground-state transition
of ortho-H$_2$D$^+$ $J_{\rm {K_a, K_c}} = 1_{10}$-$1_{11} $ by
performing interferometric and single-dish synthetic observations
using magneto-hydrodynamic simulations of high-mass collapsing
molecular cores, including deuteration chemistry. We studied different
evolutionary times and source distances (from 1 to 7 kpc) to estimate
the information loss when comparing the column densities inferred from
the synthetic observations to the column densities in the model. We
mimicked single-dish observations considering an APEX-like beam
and interferometric observations using CASA and assuming the most
compact configuration for the ALMA antennas. We found that, for
centrally concentrated density distributions, the column densities
are underestimated by about 51% in the case of high-resolution ALMA
observations ($\leqslant$1") and up to 90% for APEX observations
(17"). Interferometers retrieve values closer to the real ones, however,
their finite spatial sampling results in the loss of contribution from
large-scale structures due to the lack of short baselines. We conclude
that, the emission of o-H$_2$D$^+$ in distant massive dense cores is
faint and would require from $\sim$1 to $\sim$7 hours of observation
at distances of 1 and 7 kpc, respectively, to achieve a 14$\sigma$
detection in the best case scenario. Additionally, the column densities
derived from such observations will certainly be affected by beam
dilution in the case of single-dishes and spatial filtering in the
case of interferometers.
Title: Investigating the 21 cm signal fromthe reionization epoch
Authors: Bravo-Castillo, C.; Schleicher, D. R. G.
Bibcode: 2020BAAA...61R..85B
Altcode: 2020BAAA..61R...85B
Due to the presence of an enormous amount of neutral hydrogen during
the pre-reionization epoch of the Universe, the intergalactic medium
(IGM) can be characterized using the 21-cm line. This powerful tool will
allow us to learn about the end of the 'dark ages' when the formation
of the first structures and the first galaxies began. Once the first
galaxies emerged, the IGM was affected by the associated radiative
backgrounds. These galaxies have emitted ultraviolet radiation that
carved out ionized regions around them until hydrogen became fully
ionized, giving pass to the reionization era. We calculate the shape
of the spin temperature and the brightness temperature as a function
of redshift considering radiative heating. A particular focus of
this project will be to consider the contributions from X-ray photons
produced by the first massive black holes.
Title: Do fragmentation and accretion affect the stellar initial
mass function?
Authors: Riaz, R.; Schleicher, D. R. G.; Vanaverbeke, S.; Klessen,
R. S.
Bibcode: 2020MNRAS.494.1647R
Altcode: 2020arXiv200307639R; 2020MNRAS.tmp..723R
While the stellar initial mass function (IMF) appears to be close to
universal within the Milky Way galaxy, it is strongly suspected to be
different in the primordial universe, where molecular hydrogen cooling
is less efficient and the gas temperature can be higher by a factor of
30. In between these extreme cases, the gas temperature varies depending
on the environment, metallicity, and radiation background. In this
paper we explore if changes of the gas temperature affect the IMF of
the stars considering fragmentation and accretion. The fragmentation
behaviour depends mostly on the Jeans mass at the turning point in the
equation of state (EOS) where a transition occurs from an approximately
isothermal to an adiabatic regime due to dust opacities. The Jeans mass
at this transition in the EOS is always very similar, independent of the
initial temperature, and therefore the initial mass of the fragments
is very similar. Accretion on the other hand is strongly temperature
dependent. We argue that the latter becomes the dominant process for
star formation efficiencies above 5-7 per cent, increasing the average
mass of the stars.
Title: Resolving accretion flows in nearby active galactic nuclei
with the Event Horizon Telescope
Authors: Bandyopadhyay, Bidisha; Xie, Fu-Guo; Nagar, Neil M.;
Schleicher, Dominik R. G.; Ramakrishnan, Venkatessh; Arévalo,
Patricia; López, Elena; Diaz, Yaherlyn
Bibcode: 2019MNRAS.490.4606B
Altcode: 2019arXiv190705879B; 2019MNRAS.tmp.2508B
The Event Horizon Telescope (EHT), now with its first ever image of
the photon ring around the supermassive black hole of M87, provides
a unique opportunity to probe the physics of supermassive black holes
through Very Long Baseline Interferometry (VLBI), such as the existence
of the event horizon, the accretion processes as well as jet formation
in low-luminosity AGNs (LLAGNs). We build a theoretical model that
includes an advection dominated accretion flow (ADAF) with emission
from thermal and non-thermal electrons in the flow and a simple radio
jet outflow. The predicted spectral energy distribution (SED) of this
model is compared to sub-arcsec resolution observations to get the best
estimates of the model parameters. The model-predicted radial emission
profiles at different frequency bands are used to predict whether the
inflow can be resolved by the EHT or with telescopes such as the Global
3-mm VLBI array (GMVA). In this work the model is initially tested with
high-resolution SED data of M87 and then applied to our sample of five
galaxies (Cen A, M84, NGC 4594, NGC 3998, and NGC 4278). The model then
allows us to predict if one can detect and resolve the inflow for any
of these galaxies using the EHT or GMVA within an 8 h integration time.
Title: The 3D Structure of CO Depletion in High-mass Prestellar
Regions
Authors: Bovino, S.; Ferrada-Chamorro, S.; Lupi, A.; Sabatini, G.;
Giannetti, A.; Schleicher, D. R. G.
Bibcode: 2019ApJ...887..224B
Altcode: 2019arXiv191013981B
Disentangling the different stages of the star formation
process, in particular in the high-mass regime, is a challenge in
astrophysics. Chemical clocks could help alleviate this problem,
but their evolution strongly depends on many parameters, leading
to degeneracy in the interpretation of the observational data. One
of these uncertainties is the degree of CO depletion. We present
here the first self-consistent magneto-hydrodynamic simulations of
high-mass, star-forming regions at different scales, fully coupled
with a nonequilibrium chemical network, which includes C-N-O
bearing molecules. Depletion and desorption processes are treated
time dependently. The results show that full CO depletion (i.e., all
gas-phase CO frozen-out on the surface of dust grains) can be reached
very quickly, in one-third or even smaller fractions of the freefall
time, whether the collapse proceeds on slow or fast timescales. This
leads to a high level of deuteration in a short time, both for typical
tracers like N2H+, as well as for the main ion
{{{H}}}3+, the latter being in general larger and
more extended. N2 depletion is slightly less efficient, and
no direct effects on N-bearing molecules and deuterium fractionation
are observed. We show that CO depletion is not the only driver of
deuteration, and that there is a strong impact on D frac
when changing the grain size. We finally apply a two-dimensional
Gaussian point-spread function to our results to mimic observations
with single-dish and interferometers. Our findings suggest that the
low-values observed in high-mass star-forming clumps are in reality
masking a full-depletion stage in the inner 0.1 pc region.
Title: Discovery of a nitrogen-enhanced mildly metal-poor binary
system: Possible evidence for pollution from an extinct AGB star
Authors: Fernández-Trincado, José G.; Mennickent, Ronald; Cabezas,
Mauricio; Zamora, Olga; Martell, Sarah L.; Beers, Timothy C.; Placco,
Vinicius M.; Nataf, David M.; Mészáros, Szabolcs; Minniti, Dante;
Schleicher, Dominik R. G.; Tang, Baitian; Pérez-Villegas, Angeles;
Robin, Annie C.; Reylé, Céline
Bibcode: 2019A&A...631A..97F
Altcode: 2019arXiv190210635F
We report the serendipitous discovery of a nitrogen-rich, mildly
metal-poor ([Fe/H] = -1.08) giant star in a single-lined spectroscopic
binary system found in the SDSS-IV Apache Point Observatory
Galactic Evolution Experiment (APOGEE-2) survey, Data Release 14
(DR14). Previous work has assumed that two percent of halo giants
with unusual elemental abundances have been evaporated from globular
clusters, but other origins for their abundance signatures, including
binary mass transfer, must also be explored. We present the results of
an abundance reanalysis of the APOGEE-2 high-resolution near-infrared
spectrum of 2M12451043+1217401 with the Brussels Automatic Stellar
Parameter (BACCHUS) automated spectral analysis code. We manually
re-derive the main element families, namely light elements (C, N),
elements (O, Mg, Si), the iron-peak element (Fe), s-process element
(Ce), and light odd-Z element (Al). Our analysis confirms the N-rich
nature of 2M12451043+1217401, which has a [N/Fe] ratio of +0.69,
and shows that the abundances of C and Al are slightly discrepant
from those of a typical mildly metal-poor red giant branch star,
but exhibit Mg, Si, O and s-process abundances (Ce) of typical field
stars. We also detect a particularly large variability in the radial
velocity of this star over the period of the APOGEE-2 observations;
the most likely orbit fit to the radial velocity data has a period
of 730.89 ± 106.86 days, a velocity semi-amplitude of 9.92 ± 0.14
km s-1, and an eccentricity of ∼0.1276 ± 0.1174. These
data support the hypothesis of a binary companion, which has probably
been polluted by a now-extinct asymptotic giant branch star.
Title: Intermittent fragmentation and statistical variations during
gas collapse in magnetized atomic cooling haloes
Authors: Grete, P.; Latif, M. A.; Schleicher, D. R. G.; Schmidt, W.
Bibcode: 2019MNRAS.487.4525G
Altcode: 2019MNRAS.tmp.1506G; 2019MNRAS.tmp.1475G; 2019arXiv190300017G
Observations reveal the presence of supermassive black holes (SMBH)
as early as ∼700 million years after the big bang. Their formation
path is still subject to current debate. We explore the influence
of magnetic fields, which are strongly amplified via the turbulent
small-scale dynamo, on the formation of SMBH seeds within the direct
collapse scenario. In this study, we perform for the first time
cosmological magnetohydrodynamic large eddy simulations that employ
a model for unresolved, compressible MHD turbulence. In total we
perform 36 simulations for nine haloes each with two different initial
magnetic field strengths, and with and without employing the unresolved
turbulence model. We make use of the adaptive mesh refinement approach
to achieve an effective spatial resolution of less than one proper
astronomical unit. We consider a regime where cooling is regulated
by atomic hydrogen and the molecular hydrogen gets dissociated by a
strong radiation field. Our main finding is that the majority of the
gas properties in the haloes at the final output are predominantly
determined by the run-away gravitational collapse. Turbulence is
supersonic and super-Alfvénic in all cases, and magnetic fields are
amplified to an approximately dynamically relevant regime. Finally,
fragmentation during the collapse is intermittent and mass accretion
rates range from 0.2 to 3 M\odot yr-1. This
suggests that the presence of strongly amplified magnetic fields
and turbulence provides additional pressure support on small scales
and makes the direct collapse a viable scenario for the formation of
massive objects under the required ambient conditions.
Title: Star formation at high redshift
Authors: FFibla, P.; Bovino, S.; Riaz, R.; Díaz, V. B.; Olave, C.;
Vanaverbeke, S.; Schleicher, D. R. G.
Bibcode: 2019BAAA...61...66F
Altcode:
The importance of detailed chemical models to understand low-metallicity
star formation is widely recognized, as reflected also in recent
investigations. We present here a three-dimensional hydrodynamical
simulation for star formation. Our aim is to explore the effect of
the metal-line cooling on the thermodynamics of the star-formation
process. We explore the effect of changing the metallicity of the
gas from to . Furthermore, we explore the implications of using the
observational abundance pattern of a CEMP-no star, which have been
considered to be the missing second-generation stars. In order to
pursue our aim, we modeled the microphysics by employing the public
astrochemistry package KROME, using a chemical network which includes
sixteen chemical species (H i, H ii, H, He i, He ii, He iii, e, H i,
H ii, C i, C ii, O i, O ii, Si i, Si ii, and Si iii). We couple KROME
with the fully three-dimensional, smoothed-particle hydrodynamics
(SPH) code GRADSPH. With this framework we investigate the collapse of
a metal-enhanced cloud, exploring the fragmentation process and the
formation of stars. We found that the metallicity has a clear impact
on the thermodynamics of the collapse, allowing the cloud to reach
the CMB temperature floor for a metallicity , which is in agreement
with previous works. Moreover, we found that adopting the abundance
pattern given by the Keller star, the thermodynamics behavior is
very similar to simulations with a metallicity of , due to the high
carbon abundance. As long as only metal line cooling is considered, our
results support the metallicity threshold proposed by previous works,
which will very likely regulate the first episode of fragmentation and
potentially determine the masses of the resulting star clusters. For
a complete modeling of the IMF and its evolution, we expect that also
dust cooling needs to be taken into account.
Title: Impact of radiation backgrounds on the formation of massive
black holes
Authors: Díaz, V. B.; Schleicher, D. R. G.; Bovino, S.; FFibla, P.;
Riaz, R.; Vanaverbeke, S.; Olave, C.
Bibcode: 2019BAAA...61..166D
Altcode: 2018arXiv181201565D
The presence of supermassive black holes (SMBHs) of a few billion
solar masses at very high redshift, has motivated us to study how
these massive objects formed during the first billion years after the
Big Bang. A promising model that has been proposed to explain this,
is the direct collapse of protogalactic gas clouds. In this scenario,
very high accretion rates are needed to form massive objects early
on, and the suppression of i cooling is important in regulating the
fragmentation. Recent studies have shown that if we use a strong
radiation background, the hydrogen molecules are destroyed, favoring
the high accretion rates and therefore producing objects of very high
mass. In this work, we study the impact of UV radiation fields in a
primordial gas cloud using the recently coupled code GRADSPH-KROME for
the modeling of gravitational collapse, including primordial chemistry
to explore the fragmentation in AU scales and hence the formation
of thr first SMBHs. We found that, to suppress the formation of i,
a very high value of is required (). As shown in a previous work,
such strong radiation backgrounds are very rare, so that the direct
collapse may be difficult to achieve. Therefore, this method could
hardly explain the formation of the first SMBHs.
Title: Synthetic observations of H_2D^+ towards high-mass starless
cores
Authors: Zamponi, J.; Schleicher, D. R. G.; Bovino, S.; Giannetti,
A.; Sabatini, G.; Ferrada, S.
Bibcode: 2019BAAA...61..131Z
Altcode:
Young massive stars are usually found embedded in dense and massive
molecular clumps, and are known for being highly obscured and
distant. During their formation process, deuteration is regarded as a
potentially good indicator of the formation stage. Therefore, proper
observations of such deuterated molecules are crucial, but still, hard
to perform. In this work, we test the observability of the transition
o-HD-, using a synthetic source, to understand how the physical
characteristics are reflected in observations through interferometers
and single-dish telescopes. In order to perform such tests, we
post-processed a magneto-hydrodynamic simulation of a collapsing
magnetized core using the radiative transfer code POLARIS. Using the
resulting intensity distributions as input, we performed single-dish
(APEX) and interferometric (ALMA) synthetic observations at different
evolutionary times, always mimicking realistic configurations. Finally,
column densities were derived to compare our simulations with real
observations previously performed. Our derivations for o-HD are in
agreement with values reported in the literature, in the range of
10 cm and 10 cm for single-dish and interferometric measurements,
respectively.
Title: H-band discovery of additional second-generation stars in
the Galactic bulge globular cluster NGC 6522 as observed by APOGEE
and Gaia
Authors: Fernández-Trincado, J. G.; Zamora, O.; Souto, Diogo;
Cohen, R. E.; Dell'Agli, F.; García-Hernández, D. A.; Masseron,
T.; Schiavon, R. P.; Mészáros, Sz.; Cunha, K.; Hasselquist,
S.; Shetrone, M.; Schiappacasse Ulloa, J.; Tang, B.; Geisler, D.;
Schleicher, D. R. G.; Villanova, S.; Mennickent, R. E.; Minniti, D.;
Alonso-García, J.; Manchado, A.; Beers, T. C.; Sobeck, J.; Zasowski,
G.; Schultheis, M.; Majewski, S. R.; Rojas-Arriagada, A.; Almeida, A.;
Santana, F.; Oelkers, R. J.; Longa-Peña, P.; Carrera, R.; Burgasser,
A. J.; Lane, R. R.; Roman-Lopes, A.; Ivans, I. I.; Hearty, F. R.
Bibcode: 2019A&A...627A.178F
Altcode: 2018arXiv180107136F
We present an elemental abundance analysis of high-resolution spectra
for five giant stars spatially located within the innermost regions of
the bulge globular cluster NGC 6522 and derive Fe, Mg, Al, C, N, O, Si,
and Ce abundances based on H-band spectra taken with the multi-object
APOGEE-north spectrograph from the SDSS-IV Apache Point Observatory
Galactic Evolution Experiment (APOGEE) survey. Of the five cluster
candidates, two previously unremarked stars are confirmed to have
second-generation (SG) abundance patterns, with the basic pattern of
depletion in C and Mg simultaneous with enrichment in N and Al as seen
in other SG globular cluster populations at similar metallicity. In
agreement with the most recent optical studies, the NGC 6522 stars
analyzed exhibit (when available) only mild overabundances of the
s-process element Ce, contradicting the idea that NGC 6522 stars are
formed from gas enriched by spinstars and indicating that other stellar
sources such as massive AGB stars could be the primary polluters of
intra-cluster medium. The peculiar abundance signatures of SG stars
have been observed in our data, confirming the presence of multiple
generations of stars in NGC 6522.
Title: Black hole formation in the context of dissipative dark matter
Authors: Latif, M. A.; Lupi, A.; Schleicher, D. R. G.; D'Amico, G.;
Panci, P.; Bovino, S.
Bibcode: 2019MNRAS.485.3352L
Altcode: 2018arXiv181203104L; 2019MNRAS.tmp..644L
Black holes with masses of 10^6-10^9 M_{\odot } dwell in the
centres of most galaxies, but their formation mechanisms are not
well known. A subdominant dissipative component of dark matter with
similar properties to the ordinary baryons, known as mirror dark
matter, may collapse to form massive black holes during the epoch of
first galaxies formation. In this study, we explore the possibility
of massive black hole formation via this alternative scenario. We
perform three-dimensional cosmological simulations for four distinct
haloes and compare their thermal, chemical, and dynamical evolution in
both the ordinary and the mirror sectors. We find that the collapse of
haloes is significantly delayed in the mirror sector due to the lack
of H_2 cooling and only haloes with masses above \ge 10^7 M_{\odot }
are formed. Overall, the mass inflow rates are \ge 10^{-2} M_{\odot
} yr^{ -1} and there is less fragmentation. This suggests that the
conditions for the formation of massive objects, including black holes,
are more favourable in the mirror sector.
Title: A timeline for massive star-forming regions via deuterium
chemistry .
Authors: Giannetti, A.; Bovino, S.; Caselli, P.; Leurini, S.;
Schleicher, D. R. G.; Körtgen, B.; Menten, K. M.; Pillai, T.;
Wyrowski, F.; Sabatini, G.
Bibcode: 2019MmSAI..90..491G
Altcode:
Chemistry is an extremely powerful tool to estimate the duration of
the prestellar phase; it can provide key tools to distinguish between a
slow or a fast path towards the formation of stars. The most promising
tracers of the quiescent phase are the light, depletion-resistant
H_{2}{D}^{+} and D_{2}{H}^{+}. Our observational effort has led to the
first detections of both ortho- and para-H_{2}{D}^{+} in massive clumps
using APEX, ALMA and SOFIA. We confirm that the anticorrelation
among the abundance of o-H_{2}{D}^{+} and N_{2}{D}^{+}, a species that
can be relatively easily observed, is real and that their relative
abundance strongly decreases with evolution in the very first stages
of the star formation process. The behaviour of these species can be
explained with simple considerations on the chemical formation paths,
depletion of heavy elements, and evaporation from the dust grain
mantles, and can be used as a powerful evolutionary indicator. Our unique 3D MHD simulations, coupled with chemistry, take us
one step further than a simple relative timeline, allowing to follow
abundance variations with time. Combining these pieces of the puzzle
with the first measurement of the ortho-to-para ratio of H_{2}{D}^{+}
in a massive clump, we will have the opportunity to investigate the
duration of the quiescent phase in different mass regimes.
Title: Synthetic observations of H$_2$D$^+$ towards high-mass
starless cores
Authors: Zamponi F., Joaquin.; Schleicher, Dominik R. G.; Bovino,
Stefano; Giannetti, Andrea; Sabatini, Giovanni; Ferrada-Chamorro, Simon
Bibcode: 2018arXiv181201191Z
Altcode:
Young massive stars are usually found embedded in dense and
massive molecular clumps and are known for being highly obscured and
distant. During their formation process, deuteration is regarded as a
potentially good indicator of the formation stage. Therefore, proper
observations of such deuterated molecules are crucial, but still,
hard to perform. In this work, we test the observability of the
transition o-H$_2$D$^+(1_{10}$-$1_{11})$, using a synthetic source,
to understand how the physical characteristics are reflected in
observations through interferometers and single-dish telescopes. In
order to perform such tests, we post-processed a magneto-hydrodynamic
simulation of a collapsing magnetized core using the radiative
transfer code POLARIS. Using the resulting intensity distributions as
input, we performed single-dish (APEX) and interferometric (ALMA)
synthetic observations at different evolutionary times, always
mimicking realistic configurations. Finally, column densities were
derived to compare our simulations with real observations previously
performed. Our derivations for o-H$_2$D$^+$ are in agreement with values
reported in the literature, in the range of 10$^{\!10-11}$cm$^{\!-2}$
and 10$^{\!12-13}$cm$^{\!-2}$ for single-dish and interferometric
measurements, respectively.
Title: Star formation at high redshift
Authors: Fibla, P.; Bovino, S.; Riaz, R.; Díaz, V. B.; Olave, C.;
Vanaverbeke, S.; Schleicher, D. R. G.
Bibcode: 2018arXiv181109516F
Altcode:
We present here a three-dimesional hydrodynamical simulation for star
formation. Our aim is to explore the effect of the metal-line cooling
on the thermodynamics of the star-formation process. We explore the
effect of changing the metallicty of the gas from $Z/Z_{\odot}=10^{-4}$
to $Z/Z_{\odot}=10^{-2}$. Furthermore, we explore the implications of
using the observational abundance pattern of a CEMP-no star, which
have been considered to be the missing second-generation stars, the
so-called Pop. III.2 stars. In order to pursue our aim, we modelled the
microphysics by employing the public astrochemistry package KROME, using
a chemical network which includes sixteen chemical species (H, H$^{+}$,
H$^{-}$, He, He$^{+}$, He$^{++}$, e$^{-}$, H$_{2}$, H$_{2}^{+}$, C,
C$^{+}$, O, O$^{+}$, Si, Si$^{+}$, and Si$^{++}$). We couple KROME
with the fully three-dimensional Smoothed-particle hydrodynamics (SPH)
code GRADSPH. With this framework we investigate the collapse of a
metal-enhanced cloud, exploring the fragmentation process and the
formation of stars. We found that the metallicity has a clear impact
on the thermodynamics of the collapse, allowing the cloud to reach the
CMB temperature floor for a metallicity $Z/Z_{\odot}=10^{-2}$, which
is in agreement with previous work. Moreover, we found that adopting
the abundance pattern given by the star SMSS J031300.36-670839.3
the thermodynamics behavior is very similar to simulations with
a metallicity of $Z/Z_{\odot}=10^{-2}$, due to the high carbon
abundance. As long as only metal line cooling is considered, our
results support the metallicity threshold proposed by previous works,
which will very likely regulate the first episode of fragmentation
and potentially determine the masses of the resulting star clusters.
Title: The Extremely Active Comet C/Hale-Bopp (1995 O1): Production
Rates from Nearly Five Years of Narrowband Photometry
Authors: Bair, Allison N.; Schleicher, David G.; Farnham, Tony
Bibcode: 2018DPS....5021006B
Altcode:
Comet C/Hale-Bopp (1995 O1) was an intrinsically bright object that
exhibited the highest continuous gas and dust production rates ever
measured for a comet. We will report on our extensive narrowband
photometry observations of H-B, including 332 individual sets of
photometry obtained on a total of 98 nights at Lowell and Perth
Observatories. Our observations span nearly 5 years, beginning with
inbound measurements on 1995 July 25 (heliocentric distance, r, of
7.14 AU), continuing through perihelion (1997 April 1; perihelion
distance of 0.91 AU), then extending outbound until 2000 March 3 (r
of 10.58 AU). A thorough analysis of this dataset has been delayed
for numerous reasons, including the long timeline of post-perihelion
observations and the calibrating of our then-new HB comet filter set
(Farnham et al. 2000, Icarus 147, 180). We additionally discovered
that, due to its extremely high production rates, the size of the
collision zone for H-B was much larger than normal, especially near
perihelion, requiring an adjustment to our standard scalelengths and
an empirical adjustment to the derived water production rates. From
our first observations, it was clear that H-B was unique. The dust
production, even at 7.14 AU, had an Afρ of 50,000 cm - much higher
than that measured for any comet in our database at any heliocentric
distance. H-B's highest production rates were measured near perihelion,
where Afρ peaked at 1.2×106 cm and the water production
rate, also by far our highest value measured for any comet, reached
3.59×1031 molecules s-1. The effective active
area required to produce the measured water production is 2100
km2, implying a minimum nucleus diameter of 26 km; however
the existence of isolated jets strongly indicates that the entire
surface of the nucleus is not active, which means the actual size is
likely to be at least 2× as large. These and other results from this
unique comet will be presented. This research has been supported by
NASA's Planetary Astronomy Program.
Title: The effect of non-equilibrium metal cooling on the interstellar
medium
Authors: Capelo, Pedro R.; Bovino, Stefano; Lupi, Alessandro;
Schleicher, Dominik R. G.; Grassi, Tommaso
Bibcode: 2018MNRAS.475.3283C
Altcode: 2017arXiv171001302C; 2018MNRAS.tmp...71C; 2018MNRAS.tmp....4C
By using a novel interface between the modern smoothed particle
hydrodynamics code GASOLINE2 and the chemistry package KROME, we follow
the hydrodynamical and chemical evolution of an isolated galaxy. In
order to assess the relevance of different physical parameters and
prescriptions, we constructed a suite of 10 simulations, in which we
vary the chemical network (primordial and metal species), how metal
cooling is modelled (non-equilibrium versus equilibrium; optically thin
versus thick approximation), the initial gas metallicity (from 10 to
100 per cent solar), and how molecular hydrogen forms on dust. This
is the first work in which metal injection from supernovae, turbulent
metal diffusion, and a metal network with non-equilibrium metal cooling
are self-consistently included in a galaxy simulation. We find that
properly modelling the chemical evolution of several metal species
and the corresponding non-equilibrium metal cooling has important
effects on the thermodynamics of the gas, the chemical abundances,
and the appearance of the galaxy: the gas is typically warmer, has
a larger molecular-gas mass fraction, and has a smoother disc. We
also conclude that, at relatively high metallicity, the choice of
molecular-hydrogen formation rates on dust is not crucial. Moreover,
we confirm that a higher initial metallicity produces a colder gas
and a larger fraction of molecular gas, with the low-metallicity
simulation best matching the observed molecular Kennicutt-Schmidt
relation. Finally, our simulations agree quite well with observations
that link star formation rate to metal emission lines.
Title: Atypical Mg-poor Milky Way Field Stars with Globular Cluster
Second-generation-like Chemical Patterns
Authors: Fernández-Trincado, J. G.; Zamora, O.; García-Hernández,
D. A.; Souto, Diogo; Dell'Agli, F.; Schiavon, R. P.; Geisler, D.;
Tang, B.; Villanova, S.; Hasselquist, Sten; Mennickent, R. E.; Cunha,
Katia; Shetrone, M.; Allende Prieto, Carlos; Vieira, K.; Zasowski,
G.; Sobeck, J.; Hayes, C. R.; Majewski, S. R.; Placco, V. M.; Beers,
T. C.; Schleicher, D. R. G.; Robin, A. C.; Mészáros, Sz.; Masseron,
T.; García Pérez, Ana E.; Anders, F.; Meza, A.; Alves-Brito, A.;
Carrera, R.; Minniti, D.; Lane, R. R.; Fernández-Alvar, E.; Moreno,
E.; Pichardo, B.; Pérez-Villegas, A.; Schultheis, M.; Roman-Lopes,
A.; Fuentes, C. E.; Nitschelm, C.; Harding, P.; Bizyaev, D.; Pan,
K.; Oravetz, D.; Simmons, A.; Ivans, Inese I.; Blanco-Cuaresma, S.;
Hernández, J.; Alonso-García, J.; Valenzuela, O.; Chanamé, J.
Bibcode: 2017ApJ...846L...2F
Altcode: 2017arXiv170703108F
We report the peculiar chemical abundance patterns of 11 atypical
Milky Way (MW) field red giant stars observed by the Apache Point
Observatory Galactic Evolution Experiment (APOGEE). These atypical
giants exhibit strong Al and N enhancements accompanied by C and Mg
depletions, strikingly similar to those observed in the so-called
second-generation (SG) stars of globular clusters (GCs). Remarkably,
we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al
and N overabundances in the majority (5/7) of the metal-rich ([Fe/H]
≳ -1.0) sample stars, which is at odds with actual observations
of SG stars in Galactic GCs of similar metallicities. This chemical
pattern is unique and unprecedented among MW stars, posing urgent
questions about its origin. These atypical stars could be former SG
stars of dissolved GCs formed with intrinsically lower abundances of
Mg and enriched Al (subsequently self-polluted by massive AGB stars)
or the result of exotic binary systems. We speculate that the stars
Mg-deficiency as well as the orbital properties suggest that they
could have an extragalactic origin. This discovery should guide future
dedicated spectroscopic searches of atypical stellar chemical patterns
in our Galaxy, a fundamental step forward to understanding the Galactic
formation and evolution.
Title: Gemini and Lowell observations of 67P/Churyumov-Gerasimenko
during the Rosetta mission
Authors: Knight, Matthew M.; Snodgrass, Colin; Vincent, Jean-Baptiste;
Conn, Blair C.; Skiff, Brian A.; Schleicher, David G.; Lister, Tim
Bibcode: 2017MNRAS.469S.661K
Altcode: 2017arXiv170906552K
We present observations of comet 67P/Churyumov-Gerasimenko acquired in
support of the Rosetta mission. We obtained usable data on 68 nights
from 2014 September until 2016 May, with data acquired regularly
whenever the comet was observable. We collected an extensive set of
near-IR J, H and Ks data throughout the apparition plus visible-light
images in g΄, r΄, I΄ and z΄ when the comet was fainter. We also
obtained broad-band R and narrow-band CN filter observations when
the comet was brightest using telescopes at Lowell Observatory. The
appearance was dominated by a central condensation and the tail until
2015 June. From 2015 August onwards, there were clear asymmetries in
the coma, which enhancements revealed to be due to the presence of
up to three features (I.e. jets). The features were similar in all
broad-band filters; CN images did not show these features but were
instead broadly enhanced in the southeastern hemisphere. Modelling
using the parameters from Vincent et al. replicated the dust morphology
reasonably well, indicating that the pole orientation and locations
of active areas have been relatively unchanged over at least the
last three apparitions. The dust production, as measured by A(0°)fρ
peaked ∼30 d after perihelion and was consistent with predictions
from previous apparitions. A(0°)fρ as a function of heliocentric
distance was well fitted by a power law with slope -4.2 from 35 to
120 d post-perihelion. We detected photometric evidence of apparent
outbursts on 2015 August 22 and 2015 September 19, although neither
was discernible morphologically in this data set.
Title: A detailed framework to incorporate dust in hydrodynamical
simulations
Authors: Grassi, T.; Bovino, S.; Haugbølle, T.; Schleicher, D. R. G.
Bibcode: 2017MNRAS.466.1259G
Altcode: 2016arXiv160601229G
Dust plays a key role in the evolution of the interstellar medium
and its correct modelling in numerical simulations is therefore
fundamental. We present a new and self-consistent model that treats
grain thermal coupling with the gas, radiation balance, and surface
chemistry for molecular hydrogen self-consistently. This method can
be applied to any dust distribution with an arbitrary number of grain
types without affecting the overall computational cost. In this paper,
we describe in detail the physics and the algorithm behind our approach,
and in order to test the methodology, we present some examples of
astrophysical interest, namely (I) a one-zone collapse with complete
gas chemistry and thermochemical processes, (II) a 3D model of a
low-metallicity collapse of a minihalo starting from cosmological
initial conditions, and (III) a turbulent molecular cloud with H-C-O
chemistry (277 reactions), together with self-consistent cooling and
heating solved on the fly. Although these examples employ the publicly
available code KROME, our approach can easily be integrated into any
computational framework.
Title: The Rotation State of Comet 103P/Hartley 2
Authors: Farnham, Tony; Knight, Matthew M.; Schleicher, David G.
Bibcode: 2016DPS....4830101F
Altcode:
On November 4, 2010, the Deep Impact (DI) spacecraft made its
closest approach to comet 103P/Hartley 2, passing only 694 km from the
nucleus. Observations of the coma produced a lightcurve that shows the
nucleus is in a state of non-principal axis rotation that evolves with
time, while other observations revealed a nucleus that has concentrated
collimated jets driven by CO2 emission (A'Hearn et al.,
2011), large variability in the production of H2O and
CO2 (Besse et al. 2016), and ice patches on the surface
(Sunshine et al. 2011). To properly interpret the significance of these
phenomena, it is necessary to understand the rotation of the nucleus,
so that its thermal history can be derived and properly modeled,
while at the same time, it is likely that the comet's high activity
levels play an important role in the nucleus dynamics.An analysis of the
lightcurve by Belton et al (2013) described the comet's rotation state,
with two periodicities (primary of 18 h, secondary of 28 or 55 h) that
change with time. Although their solution describes the periodicities
observed around closest approach, it is insufficient to reproduce the
changes in coma morphology with time. We are performing an analysis of
the structures in the coma (Farnham 2009), using Monte Carlo routines
to model the outflowing dust produced by active sources on the nucleus,
to derive a comprehensive solution for the nucleus' rotation.We are also
obtaining new observations of Hartley 2 in June/July 2016 (r~3.2 AU) to
measure the nucleus' primary component period before the comet becomes
highly active. This will provide an end-state measure of the rotation
from the 2010 apparition, as well as a starting value for the current
apparition, to allow its continuing evolution to be monitored. We
will present an update on the status and preliminary results of
these analyses.This work is funded by NASA Grant NNX12AQ64G.A'Hearn,
M.F., et al. (2011) Science 332, 1396-1400Belton M.J.S., et al. (2013)
Icarus 222, 595-609.Besse, S., et al. (2016) This meeting.Farnham, T.L.,
(2009) Planetary and Space Science 57, 1192-1217.Sunshine, J.M., et al.,
(2011) EPSC-DPS Abs. 6, #1345.
Title: Star-forming dwarf galaxies: the correlation between
far-infrared and radio fluxes
Authors: Schleicher, Dominik R. G.; Beck, Rainer
Bibcode: 2016A&A...593A..77S
Altcode: 2016arXiv160700094S
The correlation between far-infrared and radio fluxes connects star
formation and magnetic fields in galaxies and has been confirmed over a
wide range in luminosities in the far-infrared to radio domain, both in
the local Universe and even at redshifts of z ~ 2. Recent investigations
have indicated that it may even hold in the regime of local dwarf
galaxies, and we therefore explore here the expected behavior in the
regime of star formation surface densities below 0.1 M⊙
kpc-2 yr-1. We derive two conditions that can be
particularly relevant for inducing a change in the expected correlation:
a critical star formation surface density to maintain the correlation
between star formation rate and the magnetic field, and a critical
star formation surface density below which cosmic-ray diffusion losses
dominate their injection through supernova explosions. For rotation
periods shorter than 1.5 × 107(H/ kpc)2 yr,
with H the scale height of the disk, the first correlation will break
down before diffusion losses are relevant because higher star formation
rates are required to maintain the correlation between star formation
rate and magnetic field strength. For high star formation surface
densities ΣSFR, we derive a characteristic scaling of
the nonthermal radio to the far-infrared and infrared emission with
ΣSFR1/3 , corresponding to a scaling of the
nonthermal radio luminosity Ls with the infrared luminosity
Lth as Lth4/3 . The latter is expected
to change when the above processes are no longer steadily maintained. In
the regime of long rotation periods, we expect a transition toward
a steeper scaling with ΣSFR2/3, implying
Ls ∝ Lth5/3 , while the regime
of fast rotation is expected to show a considerably enhanced scatter
because a well-defined relation between star formation and magnetic
field strength is not maintained. The scaling relations above explain
the increasing thermal fraction of the radio emission observed within
local dwarfs and can be tested with future observations by LOFAR as well
as the Square Kilometer Array (SKA) and its precursor radio telescopes.
Title: Witnessing the birth of a supermassive protostar
Authors: Latif, M. A.; Schleicher, D. R. G.; Hartwig, T.
Bibcode: 2016MNRAS.458..233L
Altcode: 2015arXiv151002788L; 2016MNRAS.tmp...87L
The detection of z > 6 quasars reveals the existence of supermassive
black holes of a few 109 M⊙. One of the
potential pathways to explain their formation in the infant universe
is the so-called direct collapse model which provides massive seeds
of 105-106 M⊙. An isothermal direct
collapse mandates that haloes should be of a primordial composition and
the formation of molecular hydrogen remains suppressed in the presence
of a strong Lyman Werner flux. In this study, we perform high resolution
cosmological simulations for two massive primordial haloes employing a
detailed chemical model which includes H- cooling as well as
realistic opacities for both the bound-free H- emission and
the Rayleigh scattering of hydrogen atoms. We are able to resolve the
collapse up to unprecedentedly high densities of ∼10-3
g cm-3 and to scales of about 10-4 au. Our
results show that the gas cools down to ∼5000 K in the presence of
H- cooling, and induces fragmentation at scales of about
8000 au in one of the two simulated haloes, which may lead to the
formation of a binary. In addition, fragmentation also occurs on the
au scale in one of the haloes but the clumps are expected to merge on
short time-scales. Our results confirm that H- cooling does
not prevent the formation of a supermassive star and the trapping of
cooling radiation stabilizes the collapse on small scales.
Title: Impact of Dust Cooling on Direct-collapse Black Hole Formation
Authors: Latif, M. A.; Omukai, K.; Habouzit, M.; Schleicher, D. R. G.;
Volonteri, M.
Bibcode: 2016ApJ...823...40L
Altcode: 2015arXiv150907034L
Observations of quasars at z\gt 6 suggest the presence of
black holes with a few times {10}9\quad {M}⊙
. Numerous models have been proposed to explain their
existence, including a direct collapse, which provides massive
seeds of {10}5\quad {M}⊙ . The isothermal
direct collapse requires a strong Lyman-Werner (LW) flux to quench
{{{H}}}2 formation in massive primordial halos. In this
study, we explore the impact of trace amounts of metals and dust
enrichment. We perform three-dimensional cosmological simulations
for two halos of \gt {10}7\quad {M}⊙ with
Z/{Z}⊙ ={10}-4{--}{10}-6 illuminated
by an intense LW flux of {J}21={10}5. Our
results show that initially the collapse proceeds isothermally
with T∼ 8000 K, but dust cooling becomes effective at densities
of {10}8{--}{10}12 {{cm}}-3 and
brings the gas temperature down to a few 100-1000 K for Z/{Z}⊙
≥slant {10}-6. No gravitationally bound clumps
are found in the Z/{Z}⊙ ≤slant {10}-5
cases by the end of our simulations, in contrast to the case
with Z/{Z}⊙ ={10}-4. Large inflow rates of
≥slant 0.1\quad {M}⊙ {{yr}}-1 are observed
for Z/{Z}⊙ ≤slant {10}-5, similar to a
zero-metallicity case, while for Z/{Z}⊙ ={10}-4
the inflow rate starts to decline earlier because of dust cooling and
fragmentation. For given large inflow rates, a central star of ∼
{10}4\quad {M}⊙ may form for Z/{Z}⊙
≤slant {10}-5.
Title: A chemical model for the interstellar medium in galaxies
Authors: Bovino, S.; Grassi, T.; Capelo, Pedro R.; Schleicher,
D. R. G.; Banerjee, R.
Bibcode: 2016A&A...590A..15B
Altcode: 2015arXiv151007016B
Aims: We present and test chemical models for three-dimensional
hydrodynamical simulations of galaxies. We explore the effect
of changing key parameters such as metallicity, radiation, and
non-equilibrium versus equilibrium metal cooling approximations on the
transition between the gas phases in the interstellar medium.
Methods: The microphysics was modelled by employing the public chemistry
package KROME, and the chemical networks were tested to work in a wide
range of densities and temperatures. We describe a simple H/He network
following the formation of H2 and a more sophisticated
network that includes metals. Photochemistry, thermal processes, and
different prescriptions for the H2 catalysis on dust are
presented and tested within a one-zone framework. The resulting network
is made publicly available on the KROME webpage.
Results:
We find that employing an accurate treatment of the dust-related
processes induces a faster HI-H2 transition. In addition,
we show when the equilibrium assumption for metal cooling holds and
how a non-equilibrium approach affects the thermal evolution of the
gas and the HII-HI transition.
Conclusions: These models can be
employed in any hydrodynamical code via an interface to KROME and can be
applied to different problems including isolated galaxies, cosmological
simulations of galaxy formation and evolution, supernova explosions
in molecular clouds, and the modelling of star-forming regions. The
metal network can be used for a comparison with observational data of
CII 158 μm emission both for high-redshift and for local galaxies.
Title: Comet C/2013 A1 (Siding Spring)
Authors: Schleicher, D.; Knight, M.; Skiff, B.
Bibcode: 2014CBET.4004....1S
Altcode:
D. Schleicher, Lowell Observatory, obtained two narrowband photometry
sets of comet C/2013 A1 on Oct. 20 (with the comet at r = 1.40 AU) using
the Hall 1.1-m telescope at Lowell Observatory. These observations were
acquired only about 8 hr after the comet's closest approach to Mars and
yield the following mean production rates: Q(OH; Haser) = 1.2 x 10**28
molecules/s, with an uncertainty of about 30 percent, corresponding
to Q(H_2O; vectorial) = 1.3 x 10**28 molecules/s at this distance;
Q(CN) = 1.4 x 10**25 molecules/s; Q(C_2) = 1.8 x 10**25 molecules/s;
Af(rho) at 524 nm = 260 cm (102"-diameter aperture). He also obtained
photometry on Oct. 12 (at r = 1.41 AU), with the following production
rates determined: Q(OH; Haser) = 8 x 10**27 molecules/s, with an
uncertainty of about 30 percent, corresponding to Q(H2O; vectorial)
= 9 x 10**27 molecules/s at this distance; Q(CN) = 1.4 x 10**25
molecules/s; Q(C_2) = 1.7 x 10**25 molecules/s; Af(rho) at 524 nm =
300 cm (78"-diameter aperture). These values indicate that the comet
has "typical" composition and a moderate to slightly high dust-to-gas
ratio. M. Knight and B. Skiff, Lowell Observatory, report narrowband
imaging of comet C/2013 A1 on Oct. 20 (at r = 1.40 AU, also just 8
hr after the comet's closest approach to Mars) using the Discovery
Channel Telescope. Following removal of median radial profiles, the
dust exhibited no features other than the tail, while a CN feature was
seen towards the north and east. It was brightest near position angle
0 deg and extended counterclockwise from p.a. 330 to 90 deg. Additional
CN signal was seen throughout the anti-sunward hemisphere.
Title: A UV flux constraint on the formation of direct collapse
black holes
Authors: Latif, M. A.; Bovino, S.; Van Borm, C.; Grassi, T.;
Schleicher, D. R. G.; Spaans, M.
Bibcode: 2014MNRAS.443.1979L
Altcode: 2014arXiv1404.5773L
The ability of metal-free gas to cool by molecular hydrogen in
primordial haloes is strongly associated with the strength of
ultraviolet (UV) flux produced by the stellar populations in the
first galaxies. Depending on the stellar spectrum, these UV photons
can either dissociate H2 molecules directly or indirectly
by photodetachment of H- as the latter provides the main
pathway for H2 formation in the early universe. In this
study, we aim to determine the critical strength of the UV flux above
which the formation of molecular hydrogen remains suppressed for a
sample of five distinct haloes at z > 10 by employing a higher order
chemical solver and a Jeans resolution of 32 cells. We presume that
such flux is emitted by Pop II stars implying atmospheric temperatures
of 104 K. We performed three-dimensional cosmological
simulations and varied the strength of the UV flux below the Lyman
limit in units of J21. Our findings show that the value of
J_{21}^crit varies from halo to halo and is sensitive to the local
thermal conditions of the gas. For the simulated haloes, it varies
from 400 to 700 with the exception of one halo where J_{21}^crit ≥
1500. This has important implications for the formation of direct
collapse black holes and their estimated population at z > 6. It
reduces the number density of direct collapse black holes by almost
three orders of magnitude compared to the previous estimates.
Title: The Formation of Massive Primordial Stars in the Presence of
Moderate UV Backgrounds
Authors: Latif, M. A.; Schleicher, D. R. G.; Bovino, S.; Grassi, T.;
Spaans, M.
Bibcode: 2014ApJ...792...78L
Altcode: 2014arXiv1406.1465L
Radiative feedback produced by stellar populations played a vital
role in early structure formation. In particular, photons below
the Lyman limit can escape the star-forming regions and produce a
background ultraviolet (UV) flux, which consequently may influence
the pristine halos far away from the radiation sources. These photons
can quench the formation of molecular hydrogen by photodetachment
of H-. In this study, we explore the impact of such UV
radiation on fragmentation in massive primordial halos of a few
times 107 M ⊙. To accomplish this goal, we
perform high resolution cosmological simulations for two distinct
halos and vary the strength of the impinging background UV field in
units of J 21 assuming a blackbody radiation spectrum with
a characteristic temperature of T rad = 104
K. We further make use of sink particles to follow the evolution for
10,000 yr after reaching the maximum refinement level. No vigorous
fragmentation is observed in UV-illuminated halos while the accretion
rate changes according to the thermal properties. Our findings show
that a few 102-104 solar mass protostars are
formed when halos are irradiated by J 21 = 10-500 at z
> 10 and suggest a strong relation between the strength of the
UV flux and mass of a protostar. This mode of star formation is
quite different from minihalos, as higher accretion rates of about
0.01-0.1 M ⊙ yr-1 are observed by the end of
our simulations. The resulting massive stars are potential cradles
for the formation of intermediate-mass black holes at earlier cosmic
times and contribute to the formation of a global X-ray background.
Title: Comet 209P/LINEAR
Authors: Schleicher, D.; Ye, Q. -Z.
Bibcode: 2014CBET.3880....1S
Altcode:
D. Schleicher, Lowell Observatory, obtained three sets of narrowband
photometry of comet 209P on May 19 (when the comet was at r = 1.95
AU and Delta = 0.11 AU) using the Hall 1.1-m telescope at Lowell
Observatory, resulting in the following production rates: Q(OH; Haser)
= 1.8 x 10**25 molecules/s, yielding Q(H_2O; vectorial) = 2.5 x 10**25
molecules/s at this r; Q(CN) = 5.8 x 10**22 molecules/s; Q(C_2) =
6.5 x 10**22 molecules/s; Af(rho) at 524 nm = 0.7 cm. These values
are extremely low, helping explain why this periodic comet was only
discovered ten years ago; the water production implies an effective
active area of only about 0.01 km**2. Schleicher classifies 209P's
compositional class as "typical". Note that the dust measurements and
the resulting Af(rho) value may be significantly contaminated by light
reflected from the nucleus. Quanzhi Ye, University of Western Ontario,
reports observations of comet 209P (the parent body of the potential
forthcoming May 24 Camelopardalid meteor outburst; cf. CBET 3869) with
the 8-m Gemini North telescope on Apr. 9.25 UT (27 days pre-perihelion,
at r = 1.04 AU). Spectra in the 350-600 nm range do not reveal any CN,
C_2, or C_3 emission features, which puts an upper limit of around
10**25 molecules/s for CN, around 3 x 10**24 molecules/s for C_2,
and around 10**25 molecules/s for C_3, for the production rates of
the comet. Syndyne-synchrone modeling computed by Man-To Hui (UCLA)
shows that the optical cometary tail is dominated by particles at the
level of beta = 0.0005 (where beta is the ratio of radiation pressure
to gravitational pressure; Finson and Probstein 1968, Ap.J. 154,
327). The brightest cone of the tail has tau = 25-50 days (where tau
is the lead time that the particles are released from the parent),
which corresponds to material released at r = 1.26-1.41 AU. Images
can be found at website URL http://tinyurl.com/ktzs3ck.
Title: Comet 209P/LINEAR
Authors: Schleicher, D.; Ye, Q. -Z.
Bibcode: 2014CBET.3881....2S
Altcode:
D. Schleicher, Lowell Observatory, obtained three sets of narrowband
photometry of comet 209P on May 19 (when the comet was at r = 0.99
AU and Delta = 0.11 AU) using the Hall 1.1-m telescope at Lowell
Observatory, resulting in the following production rates: Q(OH; Haser)
= 1.8 x 10**25 molecules/s, yielding Q(H_2O; vectorial) = 2.5 x 10**25
molecules/s at this r; Q(CN) = 5.8 x 10**22 molecules/s; Q(C_2) =
6.5 x 10**22 molecules/s; Af(rho) at 524 nm = 0.7 cm. These values
are extremely low, helping explain why this periodic comet was only
discovered ten years ago; the water production implies an effective
active area of only about 0.01 km**2. Schleicher classifies 209P's
compositional class as "typical". Note that the dust measurements and
the resulting Af(rho) value may be significantly contaminated by light
reflected from the nucleus. Quanzhi Ye, University of Western Ontario,
reports observations of comet 209P (the parent body of the potential
forthcoming May 24 Camelopardalid meteor outburst; cf. CBET 3869) with
the 8-m Gemini North telescope on Apr. 9.25 UT (27 days pre-perihelion,
at r = 1.04 AU). Spectra in the 350-600 nm range do not reveal any CN,
C_2, or C_3 emission features, which puts an upper limit of around
10**25 molecules/s for CN, around 3 x 10**24 molecules/s for C_2,
and around 10**25 molecules/s for C_3, for the production rates of
the comet. Syndyne-synchrone modeling computed by Man-To Hui (UCLA)
shows that the optical cometary tail is dominated by particles at the
level of beta = 0.0005 (where beta is the ratio of radiation pressure
to gravitational pressure; Finson and Probstein 1968, Ap.J. 154,
327). The brightest cone of the tail has tau = 25-50 days (where tau
is the lead time that the particles are released from the parent),
which corresponds to material released at r = 1.26-1.41 AU. Images
can be found at website URL http://tinyurl.com/ktzs3ck.
Title: Newly-formed illite preserves fluid sources during folding of
shale and limestone rocks; an example from the Mexican Fold-Thrust
Belt
Authors: Fitz-Díaz, Elisa; Camprubí, Antoni; Cienfuegos-Alvarado,
Edith; Morales-Puente, Pedro; Schleicher, Anja M.; van der Pluijm, Ben
Bibcode: 2014E&PSL.391..263F
Altcode:
We combine structural, fluid-inclusion microthermometry,
illite-crystallinity, X-Ray Diffraction (XRD) and O and H stable
isotope analyses of authigenic illite to determine the source of local
fluids interacting with rock during folding in anchizonal shales of the
Mexican Fold-Thrust Belt (MFTB). A well-exposed train of mesoscopic,
asymmetrical folds in a sequence of Cretaceous limestones interbedded
with shale was targeted for this study. We test the hypothesis that
syn-folding vein minerals and clay minerals were formed from the same
fluids by comparing the δ2H composition of inclusion fluids
in calcite and quartz from veins, and from illite concentrates from
sheared shale layers, and the sources of that fluid. Five clay
size-fractions (<0.05, 0.05-0.2, 0.2-1, 1-2, and <2 μm) were
separated from eight shale samples. In the 40 clay grain-size fractions
analyzed, illite, calcite, kaolinite, smectite, chlorite and minor
quartz were identified by XRD analysis. Most samples show different
proportions of various clay minerals, except for the finer fractions
in two of the samples (BL3 and BL4) were illite is the only clay phase
present. The discriminating potential of δ18O values of
clay is generally masked by the abundance of calcite in all samples. In
contrast, samples containing chlorite and smectite show very low values
in δ2H (-75.9 to -53.9‰), while samples containing illite
and kaolinite or pure illite show relatively high δ2H values
(-33.1 to -50.1‰). The latter fall within the δ2H range
(-39 to -49‰) determined in fluid inclusions of syntectonic veins,
indicating isotopic equilibrium between water, veins fillings and
illitic clay during deformation, according to fractionation factors
at these temperatures (220-250 °C). The δ2H values and
fluid inclusion salinities in the sampled rocks indicate that water
active during folding was partly marine and partly meteoric and
that the amount of such pore-water represented a small fraction of
the deformed rock volume. Our study demonstrates that the H-isotopic
composition of anchizonal illitic clays, commonly present in exhumed
fold-thrust belts, can be used to determine the source(s) of fluids
that were active during deformation.
Title: Primordial star formation: relative impact of H2
three-body rates and initial conditions
Authors: Bovino, S.; Schleicher, D. R. G.; Grassi, T.
Bibcode: 2014A&A...561A..13B
Altcode: 2013arXiv1307.7567B
Context. Population III stars are the first stars in the Universe
to form at z = 20-30 out of a pure hydrogen and helium gas in
minihalos of 105-106M⊙. Cooling and
fragmentation is thus regulated via molecular hydrogen. At densities
above 108 cm-3, the three-body H2
formation rates are particularly important for making the gas fully
molecular. These rates were considered to be uncertain by at least
a few orders of magnitude.
Aims: We explore the impact of
recently derived accurate three-body H2 formation for three
different minihalos, and compare them with the results obtained with
three-body rates employed in previous other studies.
Methods:
The calculations were performed with the cosmological hydrodynamics code
enzo (release 2.2) coupled with the chemistry package krome (including
a network for primordial chemistry), which was previously shown to
be accurate in high-resolution simulations.
Results: While the
new rates can shift the point where the gas becomes fully molecular,
leading to a different thermal evolution, there is no trivial trend
in the way this occurs. While one might naively expect the results to
follow the rate coefficients trend, the behavior can vary depending on
the dark-matter halo that is explored.
Conclusions: We conclude
that employing the correct three-body rates is about equally important
as the use of appropriate initial conditions, and that the resulting
thermal evolution needs to be calculated for every halo individually.
Title: Comet C/2012 S1 (Ison)
Authors: Bodewits, Dennis; Farnham, Tony; A'Hearn, M. F.; Schleicher,
D.; Ye, Quanzhi; Hui, Man-To; Gao, Xing
Bibcode: 2013CBET.3718....1B
Altcode: 2013CBET.3718....1A
Dennis Bodewits, Tony Farnham, and Michael F. A'Hearn, University
of Maryland, College Park, report results from observations of comet
C/2012 S1 using the UltraViolet-Optical Telescope (UVOT) onboard the
Swift space telescope. They obtained photometry using broadband V
(lambda_c = 546.8 nm, FWHM = 75.0 nm) and UVW1 (lambda_c = 260.0 nm,
FWHM = 70.0 nm) filters. Comet C/2012 S1 was observed on Oct. 7 at r =
1.52 AU from the sun, Oct. 20 at r = 1.27 AU, Nov. 1 at r = 0.98 AU,
and Nov. 7 at r = 0.83 AU. They derived water-production rates using
a vectorial model of 2.0 x 10**28, 1.8 x 10**28, 1.6 x 10**28, and
2.1 x 10**28 molecules/s (+/- 25 percent). The OH coma filled almost
the entire 15' x 15' field-of-view. Using smaller, fixed apertures of
projected radius 50000 km at the comet, they measured Af(rho) values of
of 750, 796, 848, and 861 cm (+/- 5 percent), respectively, normalized
to a phase of 0 degrees using the phase function by D. Schleicher
(http://asteroid.lowell.edu/comet/dustphase.html). In addition, they
further processed their Swift observations acquired in early 2013
(cf. CBET 3608) and can further constrain their upper limits for the
comet's water- production rate; using apertures with radii between 10"
and 20", they find the following 3-sigma upper limits for Q(H_2O):
Jan. 30 at r = 4.95 AU, < 8 x 10**27/s; Mar. 11 at r = 4.50 AU, <
2 x 10**27; Apr. 24 at r = 3.97 AU, < 2 x 10**27; and May 9 at r =
3.79 AU, < 1. x 10**27. Quanzhi Ye, University of Western Ontario;
Man-To Hui, Guangzhou, China; and Xing Gao, No. 1 Senior High School
of Urumqi, China, report a dramatic change of cometary morphology of
C/2012 S1 (ISON) in unfiltered CCD images taken with the 0.35-m SASP
telescope (+ QHY9 camera) at the Xingming Observatory from Nov. 13.99
to 14.99 UT. Seven tails are seen from p.a. 275 to 320 deg in the
Nov. 14 images, as opposed to only two in the Nov. 13 images. After
applying the azmuthal median model to images from both dates, two
intense jets are seen at p.a. 0 and 220 deg in the Nov. 14 images,
both being slightly skewed to the anti-solar direction and measured
to be about 34" in length. The two jets were absent in the Nov. 13
images. Images are at visible at website URL http://tinyurl.com/kefa4y4
for Nov. 13 and at URL http://tinyurl.com/l29p5x6 for Nov. 14.
Title: Massive black hole factories: Supermassive and quasi-star
formation in primordial halos
Authors: Schleicher, Dominik R. G.; Palla, Francesco; Ferrara, Andrea;
Galli, Daniele; Latif, Muhammad
Bibcode: 2013A&A...558A..59S
Altcode: 2013arXiv1305.5923S
Context. Supermassive stars and quasi-stars (massive stars with a
central black hole) are both considered as potential progenitors for
the formation of supermassive black holes. They are expected to form
from rapidly accreting protostars in massive primordial halos.
Aims: We explore how long rapidly accreting protostars remain on the
Hayashi track, implying large protostellar radii and weak accretion
luminosity feedback. We assess the potential role of energy production
in the nuclear core, and determine what regulates the evolution
of such protostars into quasi-stars or supermassive stars.
Methods: We followed the contraction of characteristic mass shells in
rapidly accreting protostars, and inferred the timescales for them to
reach nuclear densities. We compared the characteristic timescales for
nuclear burning with those for which the extended protostellar envelope
can be maintained.
Results: We find that the extended envelope
can be maintained up to protostellar masses of 3.6 × 108
ṁ3 M⊙, where ṁ denotes the accretion rate
in solar masses per year. We expect the nuclear core to exhaust its
hydrogen content in 7 × 106 yr. If accretion rates ṁ
≫ 0.14 can still be maintained at this point, a black hole may form
within the accreting envelope, leading to a quasi-star. Alternatively,
the accreting object will gravitationally contract to become
a main-sequence supermassive star.
Conclusions: Due to the
limited gas reservoir in typical 107 M⊙ dark
matter halos, the accretion rate onto the central object may drop
at late times, implying the formation of supermassive stars as the
typical outcome of direct collapse. However, if high accretion rates
are maintained, a quasi-star with an interior black hole may form.
Title: Comet C/2012 S1 (Ison)
Authors: Schleicher, D.
Bibcode: 2013IAUC.9260....1S
Altcode:
D. Schleicher, Lowell Observatory, obtained additional narrowband
photometry (cf. IAUC 9257) of comet C/2012 S1 on Sept. 14 (with
the comet at r = 1.95 AU) using the Hall 1.1-m telescope at Lowell
Observatory, resulting in the following production rates: Q(OH; Haser)
= 1.1 x 10**28, with an uncertainty of 10 percent, corresponding
to Q(H_2O; vectorial) = 1.1 x 10**28 at this distance; Q(CN) =
1.1 x 10**25; Q(C_2) = 2.0 x 10**25; Af(rho) at 524 nm = 250 cm
(97"-diameter aperture). These values indicate that the comet has
"typical" composition and a moderate-to-low dust-to-gas ratio.
Title: The Formation of Massive Population III Stars in the Presence
of Turbulence
Authors: Latif, M. A.; Schleicher, D. R. G.; Schmidt, W.; Niemeyer, J.
Bibcode: 2013ApJ...772L...3L
Altcode: 2013arXiv1306.2745L
Population III stars forming in the infant universe at z = 30 heralded
the end of the cosmic dark ages. They are presumed to be assembled in
the so-called minihalos with virial temperatures of a few thousand K
where collapse is triggered by molecular hydrogen cooling. A central
question concerns their final masses, and whether fragmentation occurs
during their formation. While studies employing Lagrangian codes suggest
fragmentation via a self-gravitating disk, recent high-resolution
simulations indicated that disk formation is suppressed. Here we
report the first high-resolution large-eddy simulations performed with
the Eulerian grid-based code Enzo following the evolution beyond the
formation of the first peak to investigate the accretion of the central
massive clump and potential fragmentation. For a total of three halos,
we see that a disk forms around the first clump. The central clump
reaches ~10 solar masses after 40 yr, while subsequent accretion is
expected at a rate of 10-2 solar masses per year. In one of
these halos, additional clumps form as a result of fragmentation which
proceeds at larger scales. We note that subgrid-scale (SGS) turbulence
yields relevant contributions to the stability of the protostellar
disks. Both with and without the SGS model, the disk evolution appears
rather stable during the timescale considered here. We conclude that
the first protostar may reach masses up to 40-100 M ⊙,
which are only limited by the effect of radiative feedback.
Title: Comet C/2012 S1 (Ison)}
Authors: Schleicher, D.
Bibcode: 2013IAUC.9257....3S
Altcode: 2013IAUC.9257C...1S
D. Schleicher, Lowell Observatory, obtained limited narrowband
photometry of comet C/2012 S1 on May 4 (when the comet was at r = 3.86
AU) using the Hall 1.1-m telescope at Lowell Observatory, resulting in
the following CN and dust production rates: b Q(CN) = 2.2 x 10**24;
Af(rho)(445.0 nm) = 270 cm, with a 62"-diameter aperture. The CN
value can be used to infer a value for Q(H_2O; vectorial) at this
heliocentric distance of about 6 x 10**26, but with viable range from
2 x 10**26 to 2 x 10**27.
Title: Comet C/2012 S1 (Ison)
Authors: Schleicher, D.
Bibcode: 2013IAUC.9254....1S
Altcode: 2013IAUC.9254A...1S
D. Schleicher, Lowell Observatory, obtained limited narrowband
photometry of comet C/2012 S1 (cf. CBET 3238) on 2013 Mar. 5 (when
at r = 4.57 AU) using the Hall 1.1-m telescope at Lowell Observatory,
resulting in the following CN and dust production rates: Q(CN) = 1.3 x
10**24; [Af(rho)] at 445 nm = 120 cm, with a 97'-diameter aperture. The
CN value can be used to infer a Q(H_2O; vectorial) value of about 3
x 10**26, but with a viable range from 1 x 10**26 to 1 x 10**27.
Title: Dark matter annihilation feedback: Effects upon collapse
and fragmentation
Authors: Smith, Rowan J.; Iocco, Fabio; Glover, Simon C. O.;
Schleicher, Dominik; Klessen, Ralf S.; Greif, Thomas; Yoshida, Naoki;
Hirano, Shingo
Bibcode: 2012AIPC.1480..418S
Altcode:
We perform the first 3D simulations to include the effects of dark
matter annihilation (DMA) in a calculation of the collapse of a
primordial halo to near stellar densities. We couple the DMA to
a time dependent chemical network, and include the effects of DMA
induced ionisation. Despite an increase in the temperature of the
halos, the gas temperature cannot rise above 2000 K due to cooling
from H2 dissociation, and a normal Population III star forms at the
centre. After the first star forms, the increased temperatures in
the disk suppress further fragmentation. In our two simulated halos,
fragmentation is suppressed completely in one, and only one secondary
protostar forms in the second. However it is possible that in the
future the baryons could become displaced from the dark matter peak
and these effects could be reduced.
Title: Anisotropy and dynamics of photospheric velocity patterns:
2D power and coherence analyses
Authors: Nesis, A.; Hammer, R.; Schleicher, H.; Roth, M.
Bibcode: 2012A&A...542A..85N
Altcode:
Context. The dynamical and topological properties of a fluid define its
hydrodynamical state and energy transfer. By means of two-dimensional
(2D) spectroscopy and 2D power and coherence analyses we study
these properties in the solar photosphere.
Aims: To obtain
insight into the change of the velocity field with height in the solar
photosphere we analyze 2D spectroscopic observations.
Methods:
Maps of the vertical velocity at four different photospheric heights
are studied by means of 2D power and coherence analyses, in order to
characterize the dynamical and topological properties of the velocity
field in the 2D wave number domain (kx,ky). (i)
The power analysis shows the power amplitude and its distribution
over the (kx,ky) domain for each velocity
map and thus height level. We use the mean azimuthal presentation
to provide a quick 1D overview. (ii) The cross-amplitude spectrum
shows interrelationships between two velocity maps. We use the
cross-amplitude spectrum to visualize and quantify changes of the
velocity patterns with height in the photosphere. (iii) The square
coherence is the normalized cross power spectrum; it represents the
correlation in the (kx,ky) domain. The degree of
isotropy of this quantity signifies the existence of velocity patterns
with different shapes. To facilitate the visualization of the 2D power
and coherence maps we calculate their 1D mean azimuthal values.
Results: The 2D power and coherence analyses reveal that the velocity
fields of the higher photospheric layers are different from the deeper
granular layers. The loss of similarity is found to occur in the mid
photosphere. The highest photospheric layers are characterized by (i)
a diminution of the velocity power; (ii) a disappearance of the small
velocity structures; and (iii) a tendency for larger upflow velocity
structures to become asymmetric.
Title: The implications of dust for high-redshift protogalaxies and
the formation of binary disks
Authors: Latif, M. A.; Schleicher, D. R. G.; Spaans, M.
Bibcode: 2012A&A...540A.101L
Altcode: 2011arXiv1110.4256L
Numerical simulations suggest that the first galaxies are formed
in protogalactic halos with virial temperatures ≥104
K. It is likely that such halos are polluted with trace amounts of
metals produced by the first generation of stars. The presence of
dust can significantly change the chemistry and dynamics of early
galaxies. In this article, we aim to assess the role of dust on the
thermal and dynamical evolution of the first galaxies in the presence
of a background UV flux, and its implications for the observability
of Lyman-α emitters and sub-mm sources. We have performed high
resolution cosmological simulations using the adaptive mesh refinement
code FLASH to accomplish this goal. We have developed a chemical
network appropriate for these conditions and coupled it with the
FLASH code. The main ingredients of our chemical model include the
formation of molecules (both in the gas phase and on dust grains),
a multi-level treatment of atomic hydrogen, line trapping of Ly-α
photons and, photoionization and photodissociation processes in a UV
background. We found that the formation of molecules (H2
and HD) is significantly enhanced in the presence of dust grains
as compared to only gas phase reactions by up to two orders of
magnitude. The presence of dust may thus establish a molecular ISM in
high-redshift galaxies. The presence of a background UV flux strongly
influences the formation of molecules by photodissociating them. We
explore the evolution after a major merger, leading to the formation
of a binary disk. These disks have gas masses of ~107
M⊙ at a redshift of 5.4. Each disk lies in a separate
subhalo as a result of the merger event. The disks are supported by
turbulent pressure due to the highly supersonic turbulence present in
the halo. For values of J21 = 1000 (internal flux), we find
that fragmentation may be enhanced due to thermal instabilities in the
hot gas. The presence of dust does not significantly reduce the Ly-α
emission. The emission of Ly-α is extended and originates from the
envelope of the halo due to line trapping effects. We also find that
dust masses of a few × 108 M⊙ are required
to observe the dust continuum emission from z ~ 5 galaxies with ALMA.
Title: Venus transit 2004: Illustrating the capability of exoplanet
transmission spectroscopy
Authors: Hedelt, P.; Alonso, R.; Brown, T.; Collados Vera, M.; Rauer,
H.; Schleicher, H.; Schmidt, W.; Schreier, F.; Titz, R.
Bibcode: 2011A&A...533A.136H
Altcode: 2011arXiv1107.3700H
The transit of Venus in 2004 offered the rare possibility to remotely
sense a well-known planetary atmosphere using ground-based absorption
spectroscopy. Transmission spectra of Venus' atmosphere were obtained
in the near infrared using the Vacuum Tower Telescope (VTT) in
Tenerife. Since the instrument was designed to measure the very bright
photosphere of the Sun, extracting Venus' atmosphere was challenging. We
were able to identify CO2 absorption lines in the upper
Venus atmosphere. Moreover, the relative abundance of the three
most abundant CO2 isotopologues could be determined. The
observations resolved Venus' limb, showing Doppler-shifted absorption
lines that are probably caused by high-altitude winds. We demonstrate
the utility of ground-based measurements in analyzing the atmospheric
constituents of a terrestrial planet atmosphere using methods that
might be applied in future to terrestrial extrasolar planets.
Title: Lyman alpha emission from the first galaxies: implications
of UV backgrounds and the formation of molecules
Authors: Latif, M. A.; Schleicher, D. R. G.; Spaans, M.; Zaroubi, S.
Bibcode: 2011A&A...532A..66L
Altcode: 2011arXiv1106.3428L
The Lyman alpha line is a robust tracer of high redshift galaxies. We
present estimates of Lyman alpha emission from a protogalactic
halo illuminated by UV background radiation fields with various
intensities. For this purpose, we performed cosmological hydrodynamics
simulations with the adaptive mesh refinement code FLASH, including
a detailed network for primordial chemistry, comprising the formation
of primordial molecules, a multi-level model for the hydrogen atom as
well as the photo-ionization and photo-dissociation processes in a UV
background. We find that the presence of a background radiation field
J21 excites the emission of Lyman alpha photons, increasing
the Lyman α luminosity up to two orders of magnitude. For a halo of
~ 1010 M⊙, we find that a maximum flux of 5
× 10-15 erg cm-2 s-1 is obtained
for J21 × fesc = 0.1, where fesc
is the escape fraction of the ionizing radiation. Depending on
the environmental conditions, the flux may vary by three orders of
magnitude. For J21 × fesc > 0.1 the Lyman
alpha luminosity decreases as the atomic hydrogen abundance becomes
rather small. The fluxes derived here can be probed using Subaru and
the upcoming James Webb Space Telescope. The emission of Lyman alpha
photons is extended and comes from the envelope of the halo rather than
its core. In the center of the halo, line trapping becomes effective
above columns of 1022 cm-2 and suppresses the
emission of Lyman alpha. In addition, cooling by primordial molecules
may decrease the gas temperature in the central region, which further
reduces Lyman α emission. In the central core, H2 is
photo-dissociated for a background flux of J21 ≥ 1000. For
weaker radiation fields, i.e. J21 < 0.1, H2
and HD cooling are particularly strong in the center of the halo,
leading to gas temperatures as low as ~100 K. We also performed a
parameter study with different escape fractions of ionizing photons and
explored the relative role of ionizing and dissociating radiation. We
find that Lyman alpha emission depends more on the strength of the
ionizing background. For a constant ionizing background, the Lyman
α flux increases at least by an order of magnitude for stronger
photodissociation.
Title: Lyman α emission from the first galaxies: signatures of
accretion and infall in the presence of line trapping
Authors: Latif, M. A.; Schleicher, Dominik R. G.; Spaans, M.;
Zaroubi, S.
Bibcode: 2011MNRAS.413L..33L
Altcode: 2011arXiv1102.0218L
The formation of the first galaxies is accompanied by large accretion
flows and virialization shocks, during which the gas is shock heated
to temperatures of ∼104 K, leading to potentially strong
fluxes in the Lyman α line. Indeed, a number of Lyman α blobs
have been detected at high redshift. In this Letter, we explore the
origin of such Lyman α emission using cosmological hydrodynamical
simulations that include a detailed model of atomic hydrogen as a
multi-level atom and the effects of line trapping with the adaptive
mesh refinement code FLASH. We see that baryons fall into the centre
of a halo through cold streams of gas, giving rise to a Lyman α
luminosity of at least 1044 erg s-1 at z =
4.7, similar to the observed Lyman α blobs. We find that a Lyman α
flux of 5.0 × 10-17 erg cm-2 s-1
emerges from the envelope of the halo rather than its centre, where
the photons are efficiently trapped. Such emission can be probed in
detail with the upcoming James Webb Space Telescope (JWST) and will
constitute an important probe of gas infall and accretion.
Title: Comet 103P/Hartley
Authors: A'Hearn, M. F.; Feaga, L. M.; Samarasinha, N. H.; Mueller,
B. E. A.; Farnham, T. L.; Knight, M.; Schleicher, D.
Bibcode: 2010CBET.2512....1A
Altcode:
M. F. A'Hearn and L. M. Feaga, on behalf of the DIXI/EPOXI science team,
report that routine sampling with the Deep Impact Medium Resolution
Imager (MRI) enabled the discovery of an unusual cometary phenomenon
on comet 103P (sometimes known by its old name, "Hartley 2") that
may recur. Between Sept. 9 and 17, the outgassing of CN, as acquired
with the CN filter (sensitive to both the dust continuum and CN gas),
increased by a factor of five and then slowly decreased, returning
to its prior trend line by Sept. 24. There was no apparent change in
the reflected continuum, acquired with a clear filter, other than a
small, gradual increase consistent with the increases before and after
this period in both CN and dust due to the decreasing range from the
spacecraft to the comet and the increasing activity of the nucleus
as it approaches the sun. This long-duration, gradual increase and
decrease of gaseous emission without any increase in the dust is
very unlike typical cometary outbursts, which have sudden onsets
and are usually accompanied by considerable dust. It is dissimilar
to the activity observed at comet 9P (old-style name "Tempel 1")
and not apparently associated with the dust-free CN jets observed in
this and other comets. Thus it is not like anything that the authors
are aware of in any other comet. Observers should be aware of this
type of activity when planning observations and interpreting their
data. In addition, H_2O and CO_2 have been unambiguously detected in
the coma using the High Resolution Instrument infrared spectrometer
(HRI-IR) on Oct. 16. N. H. Samarasinha and B. E. A. Mueller, Planetary
Science Institute; and M. F. A'Hearn and T. L. Farnham, University
of Maryland, obtained CN narrowband images at the Kitt Peak National
Observatory 2.1-m telescope from Sept. 30 to Oct. 4 UT. The enhanced
images clearly indicate the rotation of a jet feature centered around a
position angle near 30 deg. This is presumably the same feature reported
by Knight et al. (IAUC 9163). This feature moves from the northwest
towards the earth's direction, almost towards the line of sight, and
then moves to the east-northeast and finally to the far side before
starting the cycle again; while on the far side from the earth, its
level of activity decreases significantly before starting to increase
again. The repeatability of the CN morphology is consistent with a
periodicity around 17.6 hours. Small differences in the morphology
during some cycles suggest that there may be a slight rotational
excitation, probably a low-excitation short-axis mode. The CN coma
morphology is compatible with a nucleus having a high obliquity and a
retrograde rotation and suggests a low-to-mid-latitude active region
in the negative hemisphere. A preliminary estimate for the rotational
angular momentum vector is R.A. = 345 deg, Decl. = -15 deg, and the
uncertainty is as large as 20 deg in some directions. The continuum
images from the same observing run show the dust tail, but no clear
jet features are discernible. M. Knight and D. Schleicher, Lowell
Observatory, report new narrowband imaging of comet 103P using the Hall
1.1-m telescope at Lowell Observatory. Further to Knight et al. (IAUC
9163), the CN gas feature was centered at a position angle near 355
deg on 2010 Aug. 13-17, near 350 deg on Sept. 9-13, and near 350 deg
on Oct. 16, 17, and 19. Numerical modeling of these position angles
and the sense of rotation yields a rotation axis having an obliquity
of about 15 deg in the comet's orbital frame, corresponding to R.A. =
310 deg, Decl. = +80 deg, assuming principal axis rotation. Preliminary
modeling suggests that the CN jet originates at a latitude of +50 to +60
deg. An additional, fainter CN feature was seen towards the southeast
in the October 1.1-m-telescope images and in additional images obtained
Oct. 12-14 on the 0.8-m telescope at Lowell Observatory. For this pole
solution, the comet's maximum sub-Earth latitude is attained in early
October, resulting in an overlap of the two CN features towards the
east, as was observed in the Oct. 12-14 images and possibly explaining
the morphology described by Samarasinha et al. (above). With this pole
solution, the sub-earth latitude should be near the comet's equator at
the time of the EPOXI spacecraft encounter, yielding side-on corkscrews.
Title: Black Hole Formation in Primordial Galaxies: Chemical and
Radiative Conditions
Authors: Schleicher, Dominik R. G.; Spaans, Marco; Glover, Simon C. O.
Bibcode: 2010ApJ...712L..69S
Altcode: 2010arXiv1002.2850S
In massive primordial galaxies, the gas may directly collapse and form a
single central massive object if cooling is suppressed. H2
line cooling can be suppressed in the presence of a strong
soft-ultraviolet radiation field, but the role played by other cooling
mechanisms is less clear. In optically thin gas, Lyα cooling can be
very effective, maintaining the gas temperature below 104
K over many orders of magnitude in density. However, the large neutral
hydrogen column densities present in primordial galaxies render them
highly optically thick to Lyα photons. In this paper, we examine
in detail the effects of the trapping of these Lyα photons on the
thermal and chemical evolution of the gas. We show that despite the
high optical depth in the Lyman series lines, cooling is not strongly
suppressed, and proceeds via other atomic hydrogen transitions. At
densities larger than ~109 cm-3, collisional
dissociation of molecular hydrogen becomes the dominant cooling process
and decreases the gas temperature to about 5000 K. The gas temperature
evolves with density as T ∝ ρ ^{γ_eff - 1}, with γeff
= 0.97-0.98. The evolution is thus very close to isothermal, and so
fragmentation is possible, but unlikely to occur during the initial
collapse. However, after the formation of a massive central object,
we expect that later-infalling, higher angular momentum material will
form an accretion disk that may be unstable to fragmentation, which
may give rise to star formation with a top-heavy initial mass function.
Title: The sodium exosphere of Mercury: Comparison between
observations during Mercury's transit and model results
Authors: Mura, Alessandro; Wurz, Peter; Lichtenegger, Herbert I. M.;
Schleicher, Helmold; Lammer, Helmut; Delcourt, Dominique; Milillo,
Anna; Orsini, Stefano; Massetti, Stefano; Khodachenko, Maxim L.
Bibcode: 2009Icar..200....1M
Altcode:
In this study we compare the sodium exosphere observations
made by Schleicher et al. [Schleicher, H., and 4 colleagues,
2004. Astron. Astrophys. 425, 1119-1124] with the result of a detailed
numerical simulation. The observations, made during the transit
of Mercury across the solar disk on 7 May 2003, show a maximum of
sodium emission near the polar regions, with north prevalence, and the
presence of a dawn-dusk asymmetry. We interpret this distribution as
the resulting effect of two combined processes: the solar wind proton
precipitation causing chemical alteration of the surface, freeing the
sodium atoms from their bounds in the crystalline structure on the
surface, and the subsequent photon-stimulated and thermal desorption
of the sodium atoms. While we find that the velocity distribution of
photon desorbed sodium can explain the observed exosphere population,
thermal desorption seems to play a minor role only causing a smearing at
the locations where Na atoms are released on the dayside. The observed
and simulated distributions agree very well with this hypothesis and
indicate that the combination of the proposed processes is able to
explain the observed features.
Title: Influence of Primordial Magnetic Fields on 21 cm Emission
Authors: Schleicher, Dominik R. G.; Banerjee, Robi; Klessen, Ralf S.
Bibcode: 2009ApJ...692..236S
Altcode: 2008arXiv0808.1461S
Magnetic fields in the early universe can significantly alter the
thermal evolution and the ionization history during the dark ages. This
is reflected in the 21 cm line of atomic hydrogen, which is coupled to
the gas temperature through collisions at high redshifts, and through
the Wouthuysen-Field effect at low redshifts. We present a semianalytic
model for star formation and the build-up of a Lyman-α background in
the presence of magnetic fields, and calculate the evolution of the mean
21 cm brightness temperature and its frequency gradient as a function
of redshift. We further discuss the evolution of linear fluctuations
in temperature and ionization in the presence of magnetic fields and
calculate the effect on the 21 cm power spectrum. At high redshifts,
the signal is increased compared to the nonmagnetic case due to the
additional heat input into the intergalactic medium from ambipolar
diffusion and the decay of MHD turbulence. At lower redshifts, the
formation of luminous objects and the build-up of a Lyman-α background
can be delayed by a redshift interval of 10 due to the strong increase
of the filtering mass scale in the presence of magnetic fields. This
tends to decrease the 21 cm signal compared to the zero-field case. In
summary, we find that 21 cm observations may become a promising tool
to constrain primordial magnetic fields.
Title: Effects of primordial chemistry on the cosmic microwave
background
Authors: Schleicher, D. R. G.; Galli, D.; Palla, F.; Camenzind, M.;
Klessen, R. S.; Bartelmann, M.; Glover, S. C. O.
Bibcode: 2008A&A...490..521S
Altcode: 2008arXiv0803.3987S
Context: Previous works have demonstrated that the generation of
secondary CMB anisotropies due to the molecular optical depth
is likely too small to be observed. In this paper, we examine
additional ways in which primordial chemistry and the dark ages might
influence the CMB.
Aims: We seek a detailed understanding
of the formation of molecules in the postrecombination universe
and their interactions with the CMB. We present a detailed and
updated chemical network and an overview of the interactions of
molecules with the CMB.
Methods: We calculate the evolution
of primordial chemistry in a homogeneous universe and determine
the optical depth due to line absorption, photoionization and
photodissociation, and estimate the resulting changes in the CMB
temperature and its power spectrum. Corrections for stimulated and
spontaneous emission are taken into account.
Results: The
most promising results are obtained for the negative hydrogen ion
H- and the HeH+ molecule. The free-free process
of H- yields a relative change in the CMB temperature of
up to 2×10-11, and leads to a frequency-dependent change
in the power spectrum of the order 10-7 at 30 GHz. With
a change of the order 10-10 in the power spectrum, our
result for the bound-free process of H- is significantly
below a previous suggestion. HeH+ efficiently scatters CMB
photons and smears out primordial fluctuations, leading to a change
in the power spectrum of the order 10-8.
Conclusions:
We demonstrate that primordial chemistry does not alter the CMB during
the dark ages of the universe at the significance level of current CMB
experiments. We determine and quantify the essential effects that may
contribute to changes in the CMB and leave an imprint from the dark
ages, thus constituting a potential probe of the early universe.
Title: Local Helioseismology with GFPI at the Vacuum Tower Telescope,
Tenerife
Authors: Staiger, J.; Roth, M.; Wöhl, H.; Schleicher, H.; Puschmann,
K.
Bibcode: 2008ESPM...12..2.3S
Altcode:
Local Helioseimology has recently become an important tool to
investigate the Solar Interior in the vicinity of localized
phenomena like sunspots. It possibly holds the promise to give
informations about subsurface magnetic fields and material flows. We
are currently modifying the GFPI Instrument at the VTT which will
also be a First Light Instrument at GREGOR Telescope to the needs of
ground-based helioseismologic observations (GFPI: Göttingen Fabry
Perot Interferomer). The upgrade consists of a CCD-camera with a
larger Field-of-View (100"-by-100"), a modified Interfacing Hardware and
dedicated Control- and Recording-Software. Direct Interfacing to the
VTT's telescope control system allows for mosaic type patching of the
observations field. Cadence times of below 1 Minute for a 300"-by-300"
field at the telescope's resolution limit of 0.2" are possible. Data
are stored to USB-based external harddisks. An of-the-shelf beamer
allows for optical adjustments with an artificial light source. Available Preprocessing Tools allow to immediately visualize the
quality of the observational data. This includes a prelimary Ringdiagram
Analysis. Future Online Preprocessing Capabilities are to further
reduce the achievable cycle times. We will present some details
of the instrumental setup and some prelimiary observational results.
Title: Velocity Pattern Evolution Within the Photosphere
Authors: Nesis, A.; Hammer, R.; Schleicher, H.; Roth, M.
Bibcode: 2008ESPM...12.2.34N
Altcode:
The solar photosphere is the dynamical interface between the convection
zone and the chromosphere. It is compressible, convectively stable,
and affected by the overshooting granular flow. The photospheric
dynamics must thus be investigated as the continuation of the
granular dynamics as it spills over into the stable layers. We
investigate empirically the non-oscillatory small-scale velocity
field of the photosphere. We are particularly interested in the
temporal and height variations of the dynamics and its topological
behavior, i.e. in the evolution of velocity patterns in comparison
to the granular intensity patterns. Our analysis is based on
time series of 2D spectra taken with the triple etalon spectrograph
TESOS at the VTT on Tenerife. Oscillations were filtered out in
the Fourier domain. In a 2D time-series analysis, power spectra
demonstrate the rapid decay of the vertical overshoot velocities
with height by a factor 2 within less than 300 km above the surface,
thus implying a decay of the associated kinetic energy flux density
by nearly two orders of magnitude over the same height interval. As
expected, this decay of the energy flux is accompanied by a change of
the scales in the wavenumber domain. 2D coherence maps quantify the
drastic change of the pattern of the velocity field with height: While
the continuum layers are still governed by the typical granular-like
structuring with small-scale isotropy, the higher layers show elongated
patterns of upflow and downflow regions with short fragmentation and
reorganization time scales. According to a cross-correlation analysis
the extension of the granular upflows into the upper photosphere is a
strongly local process, suggesting a burst-like nature of the granular
velocity. Over the scale of the field of view, the velocity
field loses its horizontal isotropy with height. This suggests the
action of a structural instability of the deeper layers. It is an open
question which dynamical processes in the overshoot layers cause these
effects. The fragmentation and immediate reorganization of the velocity
field of the upper photosphere merit further study.
Title: Two-dimensional spectroscopy of sunspots. II. Search for
propagating waves and drifting velocity filaments in photospheric
layers
Authors: Balthasar, H.; Schleicher, H.
Bibcode: 2008A&A...481..811B
Altcode:
Aims: Running penumbral waves are often reported from observations in
chromospheric lines or lines formed in the upper photosphere. In this
work we investigate whether they can be detected in a line formed in
the mid to lower photosphere.
Methods: We used time series of
two-dimensional spectra of an iron line that is insensitive to the
magnetic field and that is formed in the lower to mid photosphere.
Results: No running penumbral waves are detected in this line formed
in the lower and mid photosphere. In the moat, outward moving velocity
features are detected. They are slightly faster than the plasma motions
but much slower than running penumbral waves.
Conclusions:
Running penumbral waves are a phenomenon occurring in higher layers,
i.e. the lower chromosphere and the upper photosphere, but not in the
mid photosphere or below. In the moat, we found long-living filamentary
velocity features drifting outwards.
Title: Propagating features in photospheric layers of sunspots
Authors: Schleicher, Helmold; Balthasar, Horst
Bibcode: 2007AN....328..717S
Altcode:
No abstract at ADS
Title: Velocity Pattern Evolution in the Solar Photosphere
Authors: Nesis, Anastasios; Hammer, Reiner; Schleicher, Helmold
Bibcode: 2007AN....328..702N
Altcode:
No abstract at ADS
Title: The Multiple Time Scales of Solar Granulation
Authors: Hammer, Reiner; Musielak, Zdzislaw E.; Nesis, Anastasios;
Routh, Swati; Schleicher, Helmold
Bibcode: 2007AN....328..703H
Altcode:
No abstract at ADS
Title: Dynamics of the solar granulation. IX. A global approach
Authors: Nesis, A.; Hammer, R.; Roth, M.; Schleicher, H.
Bibcode: 2006A&A...451.1081N
Altcode:
Based on a series of spectrograms taken with the German Vacuum Tower
Telescope (VTT) at the Observatorio del Teide (Tenerife), we study the
temporal evolution of granular dynamics and energy transport in the
photospheric layers. We consider the ensemble of the granules cut by
the spectrograph slit, modulated by wave motion, as a complex system. We
describe this ensemble by the rms of the fluctuations of the observables
along the slit: continuum intensity I, gas velocity v measured from
line center Doppler shifts with respect to the mean profile, and line
width w. The history of the rms of the observables v and w reflects the
dynamical change of the system over the 20 min observation time. We find
a burst-like change for both observables. However, the cross-correlation
between I and v remains virtually constant, with the exception of two
gaps. Using six lines of different strength we measure the rms of v in
the deep photospheric layers. On the basis of this v variation we derive
an upper limit of the kinetic energy flux as a function of height in the
photosphere for different times during the observation. The shape of the
variation with height is constant over time. A limit for the convective
enthalpy flux is calculated using the temperature variations of our
earlier models. Its shape remains the same over time. Taken together,
these results quantify the different roles that the lower and higher
photospheric layers play in the energetics of convective overshoot.
Title: Topology and dynamics of abnormal granulation
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 2005AN....326..305N
Altcode:
We present a 2D spectroscopic time series of an abnormal granulation
region and describe the formation and decay of structures, in particular
the gradual restitution of a granulation-like pattern. This behavior
is discussed in relation to magnetoconvection.
Title: Detection of neutral sodium above Mercury during the transit
on 2003 May 7
Authors: Schleicher, H.; Wiedemann, G.; Wöhl, H.; Berkefeld, T.;
Soltau, D.
Bibcode: 2004A&A...425.1119S
Altcode:
The extent of the exosphere of Mercury above the planet's limb could
for the first time be observed by detecting an excess absorption
in the solar sodium line D_2 during the transit of Mercury across
the solar disk on 2003 May 7. The observations were performed
with a 2d Fabry-Perot spectrograph of the Vacuum Tower Telescope
at Izaña, Tenerife. The absorption excess, blue-shifted by 13 pm
relative to the solar line, is mainly concentrated near the polar
regions. There, the absorption excess can be traced up to
≈700 km above the limb. Between the two polar regions, along the
eastern limb, a weaker absorption excess can be seen. A possible
streamer-like feature stretches more than 2000 km above the northern
region. Assuming the density to decrease exponentially with height,
we derive for the polar maxima vertical column densities of 3 ×
1010 cm-2, volume densities at the surface of 2.5
× 103 cm-3, and a density scale height of 150 km.
Title: Exosphere of Mercury seen as additional absorption in the Na
D2 line during the Transit on 2003 May 7.
Authors: Schleicher, H.; Wiedemann, G.; Woehl, H.; Berkefeld, T.;
Soltau, D.
Bibcode: 2004ANS...325...81S
Altcode: 2004ANS...325a..81S; 2004ANS...325..P05S
No abstract at ADS
Title: Topological changes of abnormal solar granulation surrounded
by pores.
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 2004ANS...325...77N
Altcode: 2004ANS...325..P01N; 2004ANS...325a..77N
No abstract at ADS
Title: Velocity Field of a Complex Sunspot with Light Bridges
Authors: Schleicher, H.; Balthasar, H.; Wöhl, H.
Bibcode: 2003SoPh..215..261S
Altcode:
For the leading part of sunspot group NOAA 8323, which rapidly changed
its complex structure, a time series of the line-of-sight (LOS)
component of the velocity field was obtained. With a two-dimensional
Fabry-Pérot spectrometer, the magnetically insensitive line Fe i
557.6 nm was scanned. The inclination of the LOS (heliographic angle)
to the vertical was θ=28.5°. The umbra of the observed spot was
divided by a system of light bridges into several parts. The spatial and
temporal velocity field also exhibits a considerable complexity: in one
extended umbral area there is a downward flow of 1 km s−1
relative to other dark sub-umbrae. At the center-side penumbra,
with a line-of-sight Evershed outflow of 1.5 km s−1,
a persistent patch, somewhat darker than the average penumbra, has
a LOS velocity of 1.3 km s−1 in opposite direction,
probably a downflow. At the limb-side penumbra, a photosphere-like
area is interspersed, interrupting the Evershed flow which resumes
with typical strength beyond this feature towards the outer penumbral
boundary. Most interesting is the behavior of the light bridges, which
have a slight blue shift, interrupted by short events of strong blue
or red shifts which - within the time resolution of 35 s - instantly
affect a considerable part of a light bridge.
Title: Time Variation of Statistical Properties of the Solar
Granulation
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 2003ANS...324Q..55N
Altcode: 2003ANS...324Q.P08N
No abstract at ADS
Title: Mercury Transit Observed with TESOS at the VTT on Tenerife
Authors: Schleicher, Helmold; Wöhl, Hubertus; Balthasar, Horst
Bibcode: 2003ANS...324..114S
Altcode: 2003ANS...324..P21S
No abstract at ADS
Title: Evolution of the Solar Granulation Dynamics
Authors: Nesis, Anastasios; Hammer, Reiner; Schleicher, Helmhold
Bibcode: 2003ANS...324..103N
Altcode: 2003ANS...324R.P09N
No abstract at ADS
Title: Dynamical Dichotomy of Granules Smaller and Larger than 1200 km
Authors: Nesis, Anastasios; Hammer, Reiner; Schleicher, Helmhold
Bibcode: 2003ANS...324..102N
Altcode: 2003ANS...324R.P08N
No abstract at ADS
Title: Merging and Splitting Phenomena in the Solar Granulation:
A Spectroscopic Investigation
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 2003ANS...324R..55N
Altcode: 2003ANS...324Q.P09N
No abstract at ADS
Title: Evolution of the Granular Dynamics and Energy Transport
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 2003SPD....34.0702N
Altcode: 2003BAAS...35..820N
Based on series of excellent spectrograms taken at the German Vacuum
Tower Telescope (VTT) at the Observatorio del Teide (Tenerife), we
study the temporal evolution of the granular dynamics and the energy
transport in the photospheric layers. We consider the ensemble of the
granules cut by the spectrograph slit as a complex system. We describe
this ensemble by the rms of the fluctuations of the granular observables
along the slit: continuum intensity I, Doppler velocity v, and line
width w. The history of the rms of the observables v and w reflects
the dynamical change of the system over the 20 minutes observation
time. We find for both observables a quasi-periodical change. However,
the history of the cross-correlation between I and v remains virtually
constant, with the exception of two gaps. We measure the rms of v
in the deep photospheric layers for six lines of different strength
included in the spectrograms. Using a model velocity variation based
on our previous publications, we assign photospheric heights to the
velocity measurements. These heights agree with those calculated by
other means. On the basis of this v variation we calculate the kinetic
energy flux as a function of the height in the photosphere for different
times during the observation. The form of the variation with height
turns out to be constant in time. The convective energy flux, finally,
is calculated from the measured velocity and the temperature variations
of our earlier models. Again we find practically the same variation
form over the time of the observation. Taken together, these results
quantify the different roles that the lower and higher photospheric
layers play for the energetics of the convective overshoot at the upper
boundary of the superadiabatic region of the Sun. A.N. acknowledges
travel support from the German science foundation DFG.
Title: Dynamics of the solar granulation. VIII. Time and space
development
Authors: Nesis, A.; Hammer, R.; Roth, M.; Schleicher, H.
Bibcode: 2002A&A...396.1003N
Altcode:
We study the evolution of the granulation dynamics from
the observational point of view. Based on series of excellent
spectrograms taken at the VTT, Observatorio del Teide (Tenerife), in
1999, we calculated temporal - spatial maps of the Doppler velocity,
line width, and intensity in order to track the dynamical behavior
of these observables at different positions along the spectrograph
slit. The Doppler velocity map reveals a granular dynamical time - the
characteristic time associated with the decay of the Doppler velocity
- of approximately 2 min, while the line width map does not show
any characteristic time scale but rather a strong intermittence. The
intensity map reveals the life time of the granulation as it is given
in the literature. The granular dynamical time is practically equal
to the value determined from spectrograms taken at the solar minimum
1994; so the dynamical time does not show any change over the solar
cycle. The stochastic properties of the Doppler velocity and intensity
data samples are studied (i) by means of their statistical moments and
(ii) theoretically using presupposed model distributions. For the latter
we estimated the distributions' parameters by means of the maximum
likelihood method. The histograms of the Doppler velocity variations
point to an asymmetric model distribution, while the histograms of the
intensity variations infer a symmetric one. The intensity variations
can be described well by a Gaussian probability density function, while
the Doppler velocity variations are described by the double exponential
(Gumbel) distribution, an asymmetric probability function. A remarkable
result of the statistical analysis based on both series of observations
in 1994 and 1999 is the unambiguous lack of flows with large velocity
amplitudes within the intergranular space.
Title: JOSO national report 2000-2001 - Germany
Authors: Schleicher, H.
Bibcode: 2002joso.book...67S
Altcode:
No abstract at ADS
Title: Dynamics of the solar granulation. VII. A nonlinear approach
Authors: Nesis, A.; Hammer, R.; Roth, M.; Schleicher, H.
Bibcode: 2001A&A...373..307N
Altcode:
We investigate the attractor underlying the granular phenomenon by
applying nonlinear methods to series of spectrograms from 1994 and
1999. In the three-dimensional phase space spanned by intensity, Doppler
velocity, and turbulence (line broadening), the granulation attractor
does not fill the entire phase space, as expected from the high
Reynolds and Rayleigh numbers of the photospheric plasma, but rather
shows a highly structured form. This could be due to the correlations
between intensity, turbulence, and velocity, which represent also
the Reynolds stress. To obtain insight into the dimensionality of the
attractor, we use the time lag method, a nonlinear method that enables
us to get information about the underlying attractor of a dynamical
system (granulation) from the measurement of one physical quantity
only. By applying this method to the observed Doppler velocities,
we show that the granulation attractor can be described by three
independent variables. The dimension of the granulation attractor
seems to be independent of the appearance of big granules and shear
flow. Furthermore, the power analysis of the Doppler velocity shows
power down to the spatial resolution of the instrument (0.3 arcsec). In
order to decide whether the power at the smallest scales is real or
noise, we use again the time lag method in combination with either a
high pass digital or wavelet filter, which filters out the large wave
numbers. It appears that the power at the smallest scales represents
a real signal.
Title: Dynamics of the solar granulation - On the Time Variation of
the Granular Flow
Authors: Nesis, A.; Hammer, R.; Roth, M.; Schleicher, H.; Soltau,
D.; Staiger, J.
Bibcode: 2001SoPh..200...11N
Altcode:
The emergence and evolution of large granules shows thegranular dynamics
particularly well. We therefore investigate the time dependence of
the convective flows within a regular and an exploding granule. The
observational material for this study was taken at the center of the
solar disk with the German VTT in Izaña (Tenerife, Spain) during
an observing campaign in the year 1994. It consists of series of
spectrograms of high spatial resolution, which were digitized and
processed with wavelet techniques. Among other features, our data show
the dynamical portrait of a regular and an exploding granule. We can
follow their temporal evolution over more than 12 min. Using absorption
lines of different strength we are able to see the dynamical change
of both granules at several heights within the first 200 km above
τ5000=1. The observations reveal significant changes of
the convective flow of both granules over time as well as over height,
which are discussed in detail.
Title: Development of the Dynamics of Solar Granulation in Space
and Time
Authors: Nesis, A.; Hammer, R.; Roth, M.; Schleicher, H.
Bibcode: 2001AGUSM..SP41B03N
Altcode:
We address the evolutionary behavior of the granulation dynamics from
an observational point of view by analyzing a series of excellent
spectrograms taken at the VTT in Izaña/Tenerife (Spain) in 1999. We
present temporal-spatial maps of the Doppler velocity, turbulent
line broadening, and intensity variations, which allow us to study
the dynamical behavior of these observables at different positions
on the solar surface. The Doppler velocity maps reveal a granular
dynamical time -- the time associated with the Doppler velocity decay
-- of approximately 2 min, while the turbulence map does not show
any characteristic time but a strong intermittency. The intensity
map reveals the life time of the granulation as it is given in the
literature. The granular dynamical time is practically equal to the
value determined from spectrograms taken during the solar minimum in
1994; so the dynamical time does not show any change over half a solar
cycle. The stochastical properties of the Doppler velocity and intensity
data samples were studied (i) by means of their statistical moments
and (ii) by using theoretically model distributions. For the latter
we estimated the distributions' parameters by means of the maximum
likelihood method. The histograms of the Doppler velocity variations
point to an asymmetrical model distribution, while the histograms of
the intensity variations infer a symmetrical one. Thus the intensity
variations can be described well by a Gaussian probability density
function, while the Doppler velocity variations can be described by a
Gumbel distribution an asymmetrical probability function. A remarkable
result of the statistical analysis of both the observations from 94
and 99 is the unambiguous lack of flows with large velocity amplitudes
within the intergranular space.
Title: The HB Narrowband Comet Filters: Standard Stars and
Calibrations
Authors: Farnham, Tony L.; Schleicher, David G.; A'Hearn, Michael F.
Bibcode: 2000Icar..147..180F
Altcode:
We present results concerning the development and calibration of a new
set of narrowband comet filters, designated the HB filter set, which
was designed and manufactured to replace aging IHW filters. Information
is also presented about the design and manufacturing of the filters,
including the reasoning that was used for deciding the final wavelengths
and bandpasses. The new filters are designed to measure five different
gas species (OH, NH, CN, C 2, C 3), two ions
(CO +, H 2O +), and four continuum
points. An improved understanding of extended wings from emission
bands in comet spectra, gained since the development of the IHW
filters, was incorporated into the new design, so that contamination
from undesired species is significantly reduced compared to previous
filters. In addition, advances in manufacturing techniques lead to
squarer transmission profiles, higher peak transmission and UV filters
with longer lifetimes. We performed the necessary calibrations so
that data obtained with the filters can be converted to absolute
fluxes, allowing for, among other things, accurate subtraction of
the continuum from the gas species. Flux standards and solar analogs
were selected and observed, and the data were used to establish
a magnitude system for the HB filters. The star measurements were
also used to evaluate which solar analogs were best representatives
of the Sun and to explore how the flux standards differed in the UV
with respect to their spectral type. New procedures were developed to
account for the non-linear extinction in the OH filter, so that proper
extrapolations to zero airmass can be performed, and a new formalism,
which can account for mutual contaminations in two (or more) filters,
was developed for reducing comet observations. The relevant equations
and reduction coefficients are given, along with detailed instructions
on how to apply them. We also performed a series of tests involving
factors that can affect either the filter transmission profiles or the
distribution of the emission lines in the gas species to determine how
these effects propagate through to the calibration coefficients. The
results indicate that there are only two factors that are a concern at
a level of more than a few percent: f-ratios smaller than f/ 4, and a
few individual filters whose transmission profiles are significantly
different from the filters used in the calibrations.
Title: Dynamics of the Granulation: A Non-Linear Approach
Authors: Nesis, A.; Hammer, R.; Roth, M.; Schleicher, H.
Bibcode: 2000SPD....31.0101N
Altcode: 2000BAAS...32..801N
Observables like Doppler velocity, intensity, and turbulence (line
broadening) can provide insight into the physics of the granulation
-- i.e., into the physics of the upper solar convective layers. So
far, measurements of these observables have been processed by means
of a power and coherence analysis, which is actually connected
with the physical concept of modes in linear theories. The upper
solar convective layer, however, is a highly nonlinear dissipative
system. According to theoretical considerations, such a system may
approach a strange attractor in its phase space with time. Based on a
series of spectrograms taken at the German VTT on Tenerife in the summer
of 1999, we address the granulation attractor and its dimension from
an observational point of view. In the three-dimensional phase space
spanned by the observables intensity, Doppler velocity, and turbulence,
the granulation attractor shows a high level of structuring. By means
of the time-lag and correlation integral methods applied to the Doppler
velocities we found (i) that the granulation attractor can indeed be
described by only three variables and (ii) that its dimension seems to
depend on the appearance of enhanced shear flow (shear turbulence) at
the granular borders. This means that the dynamical system underlying
the large scale granulation is a low dimension attractor. The time-lag
and correlation integral methods enable us also to decide between
noise and signal: in the case of pure noise the method does not
converge. We found that the residual velocity associated with the
small sub-granular scales does converge, however, in higher than 10
embedding dimensions. This implies that for small scale variations
the underlying attractor is not a low dimension one.
Title: Connections Between X, EUV/UV and VIS Solar Activity
Authors: Hammer, R.; Schleicher, H.
Bibcode: 2000PCEC...25..409H
Altcode:
No abstract at ADS
Title: Die Sonne im Computer.
Authors: Schleicher, H.; Stix, M.
Bibcode: 1999A&R....36Q...4S
Altcode:
No abstract at ADS
Title: Dynamics of the solar granulation. VI. Time variation of the
granular shear flow
Authors: Nesis, A.; Hammer, R.; Kiefer, M.; Schleicher, H.; Sigwarth,
M.; Staiger, J.
Bibcode: 1999A&A...345..265N
Altcode:
Excellent spectrograms can yield observational insight in the dynamics
of the solar surface not yet accessible to numerical simulations. We
present results of the elaboration of a series of spectrograms taken at
the center of the solar disk. Each of the spectrograms includes more
than 250 granules, while the series covers a time of 12 min. Our main
emphasis is to study the dynamics of the visible solar layers not only
as a function of height but also as a function of time. We investigated
the temporal and spatial behavior of the turbulent concentration at the
granular borders and its spreading-out into the intergranular space. In
the deep photosphere, enhanced turbulence is concentrated predominantly
near granular borders, while at higher layers the turbulence spreads
out over the entire intergranular space. Remarkable is the decay of the
turbulence with the height in the photosphere. There was no significant
variation of the turbulence over the 12 min. We also determined the rms
turbulent pressure at the granulation layers near tau_ {5000}=1. The
average ratio of turbulent to gas pressure is of the order of 0.1;
values of this size are also discussed in recent theoretical works. In
order to take the intermittency into account, we traced the peak to
peak variations of the turbulent velocity, which turn out to be ~
4 km sec(-1) . The corresponding ratio of turbulent to gas pressure
may thus reach locally significant values up to about 0.3. We did not
find either a correlation or an anticorrelation between turbulence
and convective flow, although the turbulence is presumably generated
by granular shear flow. We suggest that the intermittent turbulence
in the visible layers and the convective flow constitutes a dynamical
system. This turbulence-granulation-dynamical system exhibits a cyclic
behavior corresponding to the dynamical time of the granules, i.e. the
growth and decay of their velocity profile. The power spectra of the
turbulent and granular velocity show a two-component character, which
presumably reflects the action of two different processes determining
the dynamics of the solar convective boundary layers and above.
Title: Ein Blick in das Innere der Sonne.
Authors: Schleicher, H.; Stix, M.
Bibcode: 1999A&R....36....8S
Altcode:
No abstract at ADS
Title: Velocity Pulses in a Sunspot with Lightbridges
Authors: Balthasar, H.; Schleicher, H.; Wöhl, H.
Bibcode: 1999AGAb...15....7B
Altcode: 1999AGM....15..A05B
See splinter meeting SOLAR OBSERVATION WITH HIGH RESOLUTION
Title: Granulation and its variation with time
Authors: Nesis, A.; Hammer, R.; Roth, M.; Schleicher, H.
Bibcode: 1999AGAb...15...89N
Altcode: 1999AGM....15..P04N
The velocity fields on the solar surface are influenced by large
granules. They are stochastic events of convective origin which affect
the dynamics of the solar layers in various ways, for example, by
shear flow. Shear flows on the other hand produce turbulence, and thus
turbulent pressure is capable of back reacting upon the convection. This
leads to three principal questions: Is there a characteristic time
associated with the decay of the granular velocity amplitudes? What
is the nature of the attenuation of the velocity with time? What
interactions take place with the local oscillations? These questions
will be addressed through the discussion of spectrograph observations
made at the VTT.
Title: Time Variation of Granular Dynamics
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 1999soho....9E..74N
Altcode:
We found observationally well determined changes of the convective
flow of both regular and exploding granules over time as well as over
height. The attenuation of the velocity amplitude of both types of
granules must be attributed to different processes. Changes of granular
flow take place within time intervals (dynamical time) of 3 to 5 mins,
significantly shorter than the mean life time of a granule. Furthermore
the attenulation process is different at different heights in the
photosphere. The observational material for this study consists of
series of spectrograms of high spatial resolution taken at the center
of the solar disk with the German Vacuum Tower Telescope in Izana
(Tenerife, Spain) in 1994 and 1998. The series shows the dynamical
portrait of a regular and an exploding granule within the first 200
km above the continuum, which can be followed over 12 min, more than
the life time of a granule.
Title: Velocity Oscillations in Active Sunspot Groups
Authors: Balthasar, H.; Martínez Pillet, V.; Schleicher, H.; Wöhl, H.
Bibcode: 1998SoPh..182...65B
Altcode:
Time series of two-dimensional spectra were taken with the Göttingen
2D spectrometer at the VTT on Tenerife in 1996. They were investigated
for Doppler velocities and velocity oscillations in small spots and
pores of rapidly evolving sunspot groups. For the present measurements
the magnetically insensitive lines Fe i 557.6 nm and Fe i 709.0 nm
were selected.
Title: Two-dimensional spectral observations of sunspots in
chromospheric lines. I. Asymmetries of CA II lines
Authors: Ding, M. D.; Schleicher, H.
Bibcode: 1998A&A...332..767D
Altcode:
We present two-dimensional spectral observations of two closely
located small sunspots in chromospheric lines. Line asymmetries and
shifts are derived for the Caii K line in particular. It is found that
the majority of Caii K profiles show a blue asymmetry. Red asymmetry
may also appear, but only in some tiny regions. Some ephemeral blue
asymmetry patches are found in the umbrae, which seem to be related to
umbral flashes. On the limb side of the penumbra, the Caii K profiles
show a distinguishably blue asymmetry of K1. In contrast,
the profiles on the center side are more likely to possess a blue
asymmetry of K2, together with a slight red shift of
K3. We discuss possible causes for such a peculiar spatial
distribution of line asymmetries. Further line profile computations
are needed to get a consistent and satisfactory explanation.
Title: Activity and the Rotation Period of Comet Hyakutake (1996 B2)
Authors: Schleicher, David G.; Millis, Robert L.; Osip, David J.;
Lederer, Susan M.
Bibcode: 1998Icar..131..233S
Altcode:
Narrowband photometry of Comet Hyakutake (1996 B2) revealed periodic
variability in the production of dust and gas during the comet's close
approach to Earth in March 1996. The photometry alone was insufficient
to unambiguously discriminate among several possible periods, but
a unique period determination was possible by utilizing repeating
morphological features in CCD images obtained simultaneously with the
photometry on the nights of March 23-25. In particular, a large puff or
blob of material was seen to be released in the sunward direction every
6.23 ± 0.03 h. This periodic release of material, presumably from a
single dominant active region on the surface, was the source of the
observed lightcurve variations. A second, much smaller morphological
feature also repeats each cycle, confirming the value of 6.23 h for
Hyakutake's synodic rotational period.
Title: Granular Shear Flows - Influence on Helioseismology
Authors: Nesis, A.; Hammer, R.; Kiefer, M.; Schleicher, H.
Bibcode: 1998ESASP.418..829N
Altcode: 1998soho....6..829N
Over the past few years, turbulence and the associated
turbulent pressure in the upper convective layer have been
recognized as potentially important for the physics of solar
oscillations. The turbulent kinetic energy per volume, the
turbulent pressure Pturb, could affect the thickness of
the strongly superadiabatic layers and thus some of the results of
helioseismology,(see Rosenthal 1998). According to Stein and Nordlund
(1998), turbulent pressure is important in extending the mean atmosphere
in the superadiabatic layers, which lowers the eigenfrequencies of
medium and high ell modes. Our main emphasis in this paper is to provide
observational support for this influence. Series of spectrograms of
high spatial resolution, taken at the center of the solar disk with
the German Vacuum Tower Telescope in Izana (Tenerife, Spain) in 1994
and 1997, represent the observational material for this study. The
spectrograms were digitized and processed with wavelet techniques
and regression analysis. The turbulent pressure Pturb
is determined by the velocity in the granular layers. This velocity
can be measured as Doppler shifts if it is spatially resolved, and
as enhanced line widths otherwise. The resolved flow velocities are
typically found to be ~1 km sec-1, both horizontally and
vertically (Nesis and Mattig 1989). This yields a contribution to the
ratio of turbulent to gas pressure of the order of Pturb
/ Pgas 0.12. Values of this size are also discussed in
recent theoretical works (e.g., Stein and Nordlund 1998). Unresolved
velocities are observed in terms of enhanced line broadening. We find
these velocities to be highly intermittent along the slit, especially
at locations with steep velocity gradients near the borders of large
granules. In order to take this intermittency into account, we trace
the peak to peak variations of the unresolved velocity, which turn
out to be ~4km sec-1. The corresponding contribution
to the turbulent pressure near the solar surface is thus likewise
intermittent and amounts up to Pturb = 104
Pa. The ratio Pturb / Pgas may thus locally reach
significant values up to about 0.5. Furthermore, we found that resolved
and unresolved velocities in the granule/intergranule system cannot
be related by a regression line, i.e. they are neither correlated nor
anticorrelated globally. Rather the convective flow and the turbulence
should be interpreted in terms of a turbulence-granulation dynamical
system, which may indeed affect helioseismology. This system reveals
a periodic cycle similar to the growth/decay models described by
the Volterra-Lotka equations. The power spectra of the turbulent and
granular velocity show a two-component character, which presumably
reflects the action of two different processes determining the dynamics
of the solar surface layers.
Title: Dynamics of the deep solar photosphere at supergranular scales
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 1998IAUS..185..451N
Altcode:
Extending our previous studies of the dynamics of solar granulation we
investigated the relationship between granular flow and the emergence of
turbulence in the deep photosphere. Our main emphasis is to explore if
such a relationship exists, and if so, to define it quantitatively. To
this end we take advantage of the excellent signal approximation
property of wavelets. Spectrograms of high spatial resolution taken at
the center of the solar disk with the German Vacuum Tower Telescope
in Izana (Tenerife, Spain) in 1994 and 1995 represent the material
for this study. The spectrograms were digitized and processed with
wavelet techniques and regression analysis. The latter was applied to
granular convective flow and the apparently associated turbulence in
order to investigate their mutual connection. We found that granular
flow speed and turbulence cannot be related by a regression line;
rather the convective flow and the turbulence appear to be related by an
attractor in the convective flow speed--turbulence phase space. Thus,
it is well possible that the convective flow and turbulence can be
interpreted in terms of a dynamical system; and both quantities can
now be described mathematically and not only phenomenologically as
in the past. This will have consequences for our understanding of the
p-mode excitation and provide better insight into the physics of the
origin of the turbulence in the deep photosphere and its implications
for helioseismology.
Title: The Solar Intergranular Space: Time and Height Variability
Authors: Nesis, A.; Hammer, R.; Kiefer, M.; Schleicher, H.
Bibcode: 1998ASPC..154..658N
Altcode: 1998csss...10..658N
We investigate the turbulent velocity field and its interaction with
the granular flow as a function of height in the photosphere and over
one turn-over time of the granule. We are using a series of spectrograms
which includes absorption lines of different strengths. The spectrograms
were taken at the center of the solar disk with the German Vacuum Tower
Telescope (VTT) in Izana (Tenerife, Spain) in 1994. The processing of
the 7 best spectrograms from a series covering 12 min shows that the
intergranular space is always turbulent whereas the granule reveals
a practically pure laminar convective flow. In the deep photosphere,
the turbulence in the intergranular space is concentrated predominantly
near the granular border. At higher layers, however, the turbulence
spreads out over the entire intergranular space. Remarkable is the
decay of the turbulence with the height in the photosphere.
Title: Dynamics of the solar granulation. IV. Granular shear flow.
Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.; Schleicher, H.;
Sigwarth, M.; Staiger, J.
Bibcode: 1997A&A...326..851N
Altcode:
Strong velocity gradients at granular borders appear to be the source
of unresolved velocity fluctuations detectable as line broadening
variations of magnetically and thermally insensitive absorption
lines. Based on spectrograms of high spatial and spectral resolution
taken with the German Vacuum Tower Telescope(VTT) in Izana (Tenerife) we
study the strong velocity gradients and the unresolved velocity field as
well as their mutual interaction. We also investigate the variation of
these quantities with the height in the photosphere, for both a regular
and an exploding granule. By means of a coherence analysis we study,
furthermore, the extension of the convective and turbulent fluctuation
field of the granulation layers into the overlying overshoot layers as
a function of the wavenumber. The results of the coherence analysis
are consistent with, and complementary to, those obtained from the
investigation of regular and exploding granules. The small and large
scales of the convective and unresolved velocity field behave clearly
different as far as their penetration into the overlying photospheric
layers is concerned. One pressure scale height above the continuum we
find an unresolved velocity field that does not show any resemblance
to the same velocity field at the continuum level. We find that the
symmetry behavior of the unresolved velocity field with respect to
the granular flow varies with the height in the photosphere. The
unresolved velocity field could be of oscillatory, convective, or
turbulent character. However, the fact that the unresolved velocity
field is more prominent at the granular border, which is also the
location of strong shear flow, favors its turbulent character. In
this sense the granules can be seen as quasi-laminar convective flows
emerging in the turbulent field of the overshoot layers.
Title: Evolution of the Granular Shear Flow
Authors: Nesis, A.; Hammer, R.; Kiefer, M.; Schleicher, H.
Bibcode: 1997BAAS...29.1121N
Altcode:
No abstract at ADS
Title: Temporal and Spatial Variability of Parent Molecules in
Comet Hale-Bopp
Authors: Woodney, L. M.; A'Hearn, M. F.; Fernandez, Y. R.; Sherwin,
A. K.; Wellnitz, D. D.; McMullin, J. P.; Samarasinha, N.; Farnham,
T. L.; Schleicher, D. G.; Veal, J. M.; Snyder, L. E.; Wright, M. C. H.;
Forster, J. R.; Pound, M.; de Pater, I.; Helfer, T.; Plambeck, R. L.;
Engargiola, G.; Palmer, P.; Kuan, Y. -J.
Bibcode: 1997DPS....29.3701W
Altcode: 1997BAAS...29.1046W
Over the past year we have monitored the bright and exceptionally
active Comet Hale-Bopp (1995 O1). Our program has concentrated on
millimeter-wave observations of sulfur bearing molecules in an effort
to understand the total sulfur budget of the comet. Using the National
Radio Astronomy Observatory 12-m telescope on Kitt Peak we have
been observing both the long and short-term variations in H_2S, CS,
OCS and SO. Additionally, we observed H_2CS for the first time in any
comet. Near perihelion this effort expanded to include interferometric
observations with the Berkeley-Illinois-Maryland Association (BIMA)
Array. The multi-institution comet observing team obtained a wide
variety of successful observations with the array. The portion of
these data discussed here will include both maps of CS and maps of
HCN which were made simultaneously with images of the comet through a
narrow-band CN filter at Lowell Observatory. These concurrent HCN/CN
observations allow the comparison of the morphologies of a parent and
its daughter species.
Title: Hale-Bopp Imaging with the New Narrowband Comet Filters
Authors: Millis, R. L.; Schleicher, D. G.; Farnham, T. L.
Bibcode: 1997DPS....29.3213M
Altcode: 1997BAAS...29.1035M
The new narrowband comet filter set (designated the ``Hale-Bopp set'')
consists of 11 filters: five that isolate gas emission bands (OH, NH,
CN, C_3, and C_2), two for ions (CO(+) and H_2O(+) ) and four that
isolate associated continuum bands. Based on the knowledge gained from
the IHW filter set, many improvements were made in the new filters,
including a reduction of the continuum filter contamination from gas
emissions. Also, advancements in the manufacturing process produced
higher transmissions, squarer profiles and more robust, longer-lived
UV filters. Forty-seven full or partial filter sets were distributed
early in 1997. The status of both the standard star system and the
calibration process will be presented. Our own filters were extensively
used for both photometry and imaging of Comet Hale-Bopp from January
to May. Near-nucleus images were obtained in all wavelengths with the
Lowell Hall 42'' telescope and a 2048(2) CCD. The continuum images show
arc structures that change from night to night and can be measured to
obtain information about the nucleus rotation and dust velocities. The
CO(+) images show detailed structures that comprise the extensive
plasma tail, but the images taken through the H_2O(+) filter exhibit
little structure apart from what is seen in the dust images. The
neutral gas images are dominated by a large contribution from the
background continuum; however, even a preliminary (uncalibrated)
continuum subtraction reveals many details hidden by the underlying
dust. Wide-field images of Hale-Bopp were also obtained through
the narrowband filters, using the 2048(2) CCD mounted on an 8-inch
f/4 Takahashi telescope. These images have a 3(deg) field of view,
which captures 10-15 million kilometers of the tail. In these images,
the dust tail is well defined with a high signal-to-noise ratio but
exhibits very little structure. The CO(+) images, on the other hand,
show complex structure, which was observed to change on time scales
as short as 30 minutes.
Title: Uniform Analysis of IUE Spectra of Comets
Authors: Budzien, S. A.; Schleicher, D. G.; Dymond, K. F.
Bibcode: 1997DPS....29.2914B
Altcode: 1997BAAS...29Q1031B
The International Ultraviolet Explorer (IUE) satellite has provided a
large database of cometary spectra over a period of 18 years. During the
IUE lifetime varying solar activity levels, instrumental degradation,
data processing revisions, evolving coma models, and our growing
understanding of comets have rendered previous IUE cometary surveys
incomplete or difficult to compare. The IUE spacecraft was retired in
1996. We have performed a uniform reduction of over 400 mid-ultraviolet
(2000--3000 Angstroms) cometary spectra in the final archive (NEWSIPS)
data format. We use automated data reduction techniques developed for
handling large volumes of UV airglow data expected from upcoming NRL
satellite experiments. We derive gas production rates for H_2O, CS, NH,
and various minor species, set upper limits to undetected emissions
features, and calculate the Afrho parameter for dust-scattered solar
radiation. Solar activity and sensitivity degradation effects have
been taken into account. The production rates, abundance ratios, dust
parameters, and cometary orbital data are analyzed and discussed with
respect to chemical evolution of comae, compositional classes of comets,
and the results of ground-based photometric surveys.
Title: Lyman continuum as a diagnostic for nonthermal processes in
solar flares.
Authors: Ding, M. D.; Schleicher, H.
Bibcode: 1997A&A...322..674D
Altcode:
We have computed the Lyman continuum intensities for different flare
circumstances, namely, the temperature rise in the chromosphere, the
downward shift of the transition region, and the nonthermal effect of a
precipitating beam of electrons. All the three factors can enhance the
intensity by various amounts. The third effect additionally lowers the
color temperature of the Lyman continuum. It thus provides a diagnostic
tool to discriminate whether there exists an obvious nonthermal effect
of electron beam bombardment during solar flares. It is also suggested
that the relative magnitudes of Lyman and Balmer continuum enhancements
can be used to infer the energy distribution type of the beam electrons.
Title: Comet 81P/Wild 2
Authors: Farnham, T.; Schleicher, D.; Hornoch, K.; Znojil, V.; Pereira,
A.; Bortle, J. E.; Granslo, B. H.
Bibcode: 1997IAUC.6597....2F
Altcode:
T. Farnham and D. Schleicher, Lowell Observatory, report on narrow-band
photometry of comet 81P with the 0.79-m telescope on Mar. 5.4 UT,
at r = 1.70: "Haser-model production rates were log Q(OH) = 27.77,
log Q(CN) = 25.25, and log Q(C2) = 24.92, and the dust-production
rate was log (Af rho) = 2.63; combining these results with those
previously obtained with the Hall telescope on Feb. 12.2 and 15.2 (r
= 1.78-1.77 AU) implies that gas and dust production are essentially
unchanged over this three-week interval." Further total visual magnitude
estimates: Mar. 4.78 UT, 9.5 (K. Hornoch, Lelekovice, Czech Rep., 0.35-m
reflector); 7.76, 9.6 (V. Znojil, Brno, Czech Rep., 25x100 binoculars);
11.92, 9.9 (A. Pereira, Cabo da Roca, Portugal, 0.25-m reflector);
13.09, 9.7 (J. E. Bortle, Stormville, NY, 0.41-m reflector); 16.91,
9.7 (B. H. Granslo, Fjellhamar, Norway, 0.20-m reflector).
Title: Velocity oscillations in active sunspot groups.
Authors: Balthasar, H.; Martínez Pillet, V.; Schleicher, H.; Wöhl, H.
Bibcode: 1997AGAb...13...12B
Altcode:
No abstract at ADS
Title: The Velocity Field in and around Sunspots. Results from
2D-Spectroscopy
Authors: Balthasar, H.; Schleicher, H.
Bibcode: 1997ASPC..118..111B
Altcode: 1997fasp.conf..111B
A sunspot was observed on June 11, 1995 with the Gottingen
2D-spectrometer at the Vacuum Tower Telescope on Tenerife using the
line Fe 709 nm. The data show an radial outflow of 500 m/s outside
the penumbra for about 15000 km. This flow is separated from the
Evershed flow of 1.6 km/s by a sharp decrease at the boundary of the
visible penumbra. The Evershed flow is associated to dark penumbral
filaments, but we do not find a correlation between intensities and
line asymmetries. No relation between the power distribution and the
filaments is found for the 5 minute oscillations. Small spots and
pores in the vicinity of the main spot show 3 minute oscillations.
Title: Two-dimensional spectroscopy of sunspots. I. Intensity,
velocity, and velocity power maps of a sunspot.
Authors: Balthasar, H.; Schleicher, H.; Bendlin, C.; Volkmer, R.
Bibcode: 1996A&A...315..603B
Altcode:
A time series of two-dimensional spectra of a sunspot at θ=~45°
has been obtained with a spectrometer based on a Fabry-Perot
interferometer. From our observations in the FeI line at 709.04nm we
find that the gas plasma in the vicinity of the sunspot (the moat)
has a velocity of about 500m/s directed outwards. Nevertheless,
the Evershed flow shows a sharp decrease by about 1000m/s at the
outer boundary of the visible penumbra. The mean white-light image
averaged over 1^h^52^m^ still shows radial structures in the penumbra,
indicating their long lifetime. Spatial variations of the velocities
and continuum intensities have correlation coefficients of +0.66
for the centre-side penumbra and -0.57 for the limb-side one. The
correlation coefficients increase to +/-0.75 for the line-centre
intensities. This correlation confirms that the Evershed effect is
related to the dark filaments. Outside the spot, the long-time average
images of the continuum and the line-centre intensities show a chain of
bright dots with a size of about one arcsec and intensities up to 4.5%
higher than their surroundings. These dots are related to the outer
boundary of the velocity field in the moat. In the five-minute range,
velocity power spectra show a decrease in the umbra and in the penumbra,
but no dependence on the radial structure. In the range between eight
and twenty minutes, power is present in the centre-side penumbra; it
resembles that of granular areas, but it has a radial structure. In
the umbra or the limb-side penumbra, the power values are much lower.
Title: The Lyman continuum as a diagnostic for nonthermal processes
in solar flares.
Authors: Ding, M. D.; Schleicher, H.
Bibcode: 1996AGAb...12..163D
Altcode:
No abstract at ADS
Title: Turbulent and convective velocity fields in the solar
photosphere.
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 1996AGAb...12..164N
Altcode:
No abstract at ADS
Title: Coma Morphology of Comet Hyakutake (1996 B2) Using Narrowband
Imaging
Authors: Lederer, S. M.; Schleicher, D. G.; Osip, D. J.; Millis, R. L.
Bibcode: 1996DPS....28.0911L
Altcode: 1996BAAS...28.1090L
Data for morphological studies of Comet Hyakutake (1996 B2) were
obtained from Lowell Observatory. Narrowband filter images of the
comet were taken on the nights of Mar 23-25, 1996, the weekend
of closest approach. Central wavelengths of the filters include
3871Angstroms (CN), 4060 (C_3), 4260Angstroms (CO+), 4845Angstroms
(Cont), 5139Angstroms (C_2), 6840Angstroms (Cont), 7025 Angstroms
(H_2O +) as well as a wideband R filter. The images, taken with
the Hall 1m telescope, have a scale of .72''/pixel (4.8' per side)
or 1.92 x 10(5) km/pixel at closest approach. Further, we obtained
images on the nights of Mar 29-30 with a wide--field Takahashi .2m
telescope using the same narrowband filters. These images form a
complementary set to the earlier images as they have a scale of 7.76
''/pixel (51.7' per side). 20 pixels in the Takahashi images (Mar
30) covers the entire 1m closest approach field of view. In order to
investigate the detailed morphology present in the coma of Hyakutake,
we performed a sequence of procedures designed to remove the gross,
overall fall--off of material with increasing distance from the
nucleus. After bias subtracting and flat--fielding, the images were
shifted, trimmed, and normalized to assist in intercomparisons. Mean,
azimuthally--averaged radial profiles were determined for each
bandpass on each night. These were used to create radially symmetric
models. We then ratioed each processed image by the model created for
its corresponding filter. The results show underlying details including
temporal changes and sunward--tailward assymmetries. For instance,
continuum images clearly show a a sunward--moving blob of material
ejected once per rotation of 6.24 hours. The gas images show a similar
but less prominent structure moving away from the nucleus which may
be due to the underlying continuum present within those filters. In
addition, the tail's brightness can be more than twice as high as the
sunward blob in the continuum images, but very little sunward/tailward
brightness difference exists in the CN images. These and other details
will be presented and discussed.
Title: Dynamics of the solar granulation. V. The intergranular space.
Authors: Nesis, A.; Hammer, R.; Hanslmeier, A.; Schleicher, H.;
Sigwarth, M.; Staiger, J.
Bibcode: 1996A&A...310..973N
Altcode:
This investigation is based on a spectrogram of extraordinary spatial
resolution selected from a series of 80 spectrograms taken with the
vacuum tower telescope at Izana (Tenerife) in May 1994. The wavelength
range was λλ: 491.00-491.40nm and includes both magnetically sensitive
and insensitive spectral lines. The spectrograph slit intersected parts
of the border and interior of CaII network cells, thus permitting a
comparative study of the granular dynamics at varying, but moderate,
levels of magnetic activity. As diagnostic tools we use the Doppler
shift variation of line cores, which is associated with spatially
resolved velocity structures, and the line broadening variation,
which is a signature of unresolved velocity fluctuations. We discuss
in particular the granular dynamics and the intermittency of the
line broadening within the intergranular space as functions of height
and position relative to network cells. Our results suggest that the
magnetic field in the network is not only located preferentially in
the intergranular space, but furthermore coincides with regions of
enhanced line broadening. We confirm that the Doppler shift variation
is reduced in regions of enhanced magnetic field, but we find that this
reduction affects the entire range of granular scales. The slopes of
the velocity power spectra are independent of the magnetic activity
level. This result is surprising, since on the basis of classical MHD
turbulence theory one would have expected shallower power spectra in
magnetically active regions. The line broadening variation is much
less sensitive to the magnetic field than the line shift variation.
Title: A search for formation-height oscillations in umbrae.
Authors: Berger, B.; Balthasar, H.; Schleicher, H.; Wiehr, E.;
Woehl, H.
Bibcode: 1996A&A...310..328B
Altcode:
The formation heights of spectral lines and continua in sunspots can be
determined by measuring the apparent distance of the spot relative to
the nearby solar limb. In order to confirm the existence of oscillatory
variations of such limb distances and to exclude possible influences
of differential image motion between the spot and the nearby limb, we
have obtained time series observations of the lines Ca^+^ 8542, Mg b,
and the non-magnetic line Fe 5576 simultaneously on two telescopes. No
indication is found for periodic fluctuations of the spot's apparent
limb distance. Only one of the seven time series shows a significant
40 min period of the line core but not of the continuum in the data
from both telescopes. This variation of the line formation height,
however, may be attributed to parallel guiding corrections of a
spatially inhomogenous umbral chromosphere. The other time series
show different periods for the two telescopes, which must be caused
by unrelated guiding corrections.
Title: On the Turbulence of the Solar Photosphere
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 1996AAS...188.0202N
Altcode: 1996BAAS...28..820N
Velocity fields of convective origin and unresolved velocity
fluctuations ("turbulence spots") are distributed on the solar surface
in characteristic ways. The velocity field fluctuations (measured as
Doppler shifts) show a pattern similar to that of the granulation,
while the turbulence spots are concentrated in the intergranular space
near the granular borders and are apparently connected with shear
flows. Doppler velocity fields as well as turbulence spots are tightly
connected with the dynamics of the granular layers but seem to influence
the overlying layers. Emerging ordered laminar convective flows produce
shear flows which subsequently generate turbulence, apparently a major
controller of the atmospheric dynamics of the sun. A central issue is
the extension of the granular dynamics into the overlying photospheric
layers. In this investigation we address mainly the turbulence spots:
the change of their distribution with height in the photosphere, their
generation, and their relationship to the granular velocity. We are
also interested in the granular velocity patterns and their extension
into the photospheric layers. Our observational material consists
of spectrograms of excellent spectral and spatial quality. Doppler
velocity field and turbulence are measured simultaneously at various
heights in the photosphere by means of absorption lines of different
strength. To investigate the extension of the influence of the
granular dynamics into the photospheric layers we use the coherence
analysis, which makes use of the characteristic dynamical patterns
of the turbulence and Doppler velocity. We find that the small scale
turbulence pattern changes rapidly with height over a scale of one
pressure scale height. This result can be seen as a manifestation of
lateral diffusion of turbulence in the intergranular space after its
generation by the shear flow at granular borders. This explains the
turbulent state of the intergranular space.
Title: Narrowband Photometry and Imaging of Comet Hyakutake (1996 B2)
Authors: Schleicher, D. G.; Millis, R. L.; Osip, D. J.; Lederer, S.
Bibcode: 1996AAS...188.6206S
Altcode: 1996BAAS...28..926S
We present analysis of both narrowband photometry and CCD imaging of
Comet Hyakutake (1996 B2) obtained at Lowell Observatory using the IHW
comet filters. Photometry results include production rates measured
for OH, NH, CN, C_2, C_3, and a measure of the dust production, Afrho
. Several hundred CCD images were obtained in filters isolating CN, C_2,
C_3, CO(+) , and H_2O(+) , and continuum at 4845 Angstroms and 6840
Angstroms. Moderate time resolution (of order 10-30 minutes) in both
the photometry and the imaging over three nights near closest approach
to Earth enables us to evaluate temporal variations in the various
emission species and dust, related to the comet's rotational state and
active area distribution. Well--defined periodic brightness variations
were measured and are consistent with single--peaked lightcurves with
periods of about either 6.25 or 8.55 hr, or double--peaked lightcurves
with periods of 9.80, 12.45, 13.0, or 17.2 hr. Preliminary analysis
of the imaging data indicates the morphology repeats with a period of
between 6.0 and 6.4 hr within an individual night, but not for other
periods less than 10 hr. The combined results strongly imply that the
rotation period of the comet is approximately 6.25 hr and that a single
active region controls the photometric variations. Photometry from
the night of closest approach (25 March) yield mean production rates
(log Q(X) molecules/sec) of: 28.93 for OH; 26.60 for CN; and 26.78 for
C_2, while the log of the dust production was 3.75. Production rates
the prior two nights were significantly higher. Additional photometric
data obtained prior to and after closest approach indicated that the
dependence of the gas species initially was flat or very shallow with
heliocentric distance but then sharply steepened, while that of the dust
has maintained a constant slope of -2.5 [cf. IAUC 6344]. The ratio of
the trace species to water (as measured by OH) classify this comet as
``typical'' in our current taxonomy [cf. A'Hearn et al., 1995, Icarus
118, 223-270].
Title: Comet C/1996 B2 (Hyakutake)
Authors: Schleicher, D.; Osip, D.; Lederer, S.; Millis, R.; Wasserman,
L.; Luethen, H.; Bouma, R. J.; Shanklin, J. D.
Bibcode: 1996IAUC.6372....1S
Altcode:
D. Schleicher, Lowell Observatory, communicates: "Narrowband photometry
of comet C/1996 B2 was obtained by D. Osip and S. Lederer (University
of Florida) using the 0.79-m telescope at Lowell Observatory on
Mar. 23.2-23.5 UT (r = 1.08 AU), Mar. 24.2- 24.5 (1.06 AU), and
Mar. 25.1-25.2 (1.05 AU). Mean Haser-model production rates for the
three dates, respectively, were: log Q(OH) = 29.17, 29.18, and 28.93;
log Q(CN) = 26.69, 26.67, and 26.60; log Q(C2) = 26.86, 26.84, and
26.78. The dust-production rates were log [Af(rho)] = 3.91, 3.82, and
3.75. Additional photometry was obtained by R. Millis, D. Schleicher,
and L. Wasserman using the Hall 1.07-m telescope at Lowell Observatory
on Mar. 29.1-29.3 (0.96 AU) and 30.1-30.2 (0.94 AU). Production
rates for these dates were: log Q(OH) = 28.88 and 28.89; log Q(CN)
= 26.56 and 26.58; log Q(C2) = 26.73 and 26.77; and log [Af(rho)] =
3.80 and 3.85. Combining these results with those previously obtained
(cf. IAUC 6344) indicates that production was systematically high on
Mar. 23 and 24, particularily for OH, and returned to near-baseline
slopes on the Mar. 25, 29, and 30. The high values on Mar. 23 and
24 may be related to the 'luminous knots' reported by Lecacheux et
al. (IAUC 6354) on Mar. 23.9-24.2. Well-defined periodic brightness
variations were observed on all five nights for all species, with a
typical amplitude in the log of about 0.1 each night. Single-peaked
lightcurves with periods of about 6.25 or 8.55 hr are viable,
while double-peaked lightcurves with periods of 9.80, 12.45, 13.0,
or 17.2 hr are also acceptable. Periods shorter than about 5 hr are
ruled out. The single-peaked periods are slightly longer than the
periods proposed by Lecacheux et al. (cf. IAUC 6354). Narrowband CCD
imaging by D. Schleicher, R. Millis, and L. Wasserman using the Hall
telescope on Mar. 23, 24, and 25 shows distinct morphological structure
varying on a timescale of well less than 1 hr. Preliminary analysis
indicates the morphology repeats with a period of between 6.0 and 6.4
hr within an individual night, while the structure does not repeat for
any other period less than 10 hr. The imaging results, combined with
the lightcurve results, strongly imply that the comet has a rotation
period of about 6.25 hr and that a single active region controls the
photometric variations." Total visual magnitude estimates: Apr. 2.81
UT, 2.2 (H. Luethen, Hamburg, Germany, 10x50 binoculars); 3.99, 2.1
(R. J. Bouma, Groningen, Netherlands, naked eye; tail 18 deg long;
during total lunar eclipse); 4.00, 2.3 (J. D. Shanklin, Brinkley,
England, naked eye; tail 7 deg long in p.a. 44 deg).
Title: Comet C/1996 B2 (Hyakutake)
Authors: Womack, M.; Festou, M. C.; Stern, S. A.; Millis, R.;
Schleicher, D.; Granslo, B. H.; Cernis, K.; O'Meara, S.; Pravec, P.;
Marsden, B. G.; Scotti, J. V.; Morris, C. S.
Bibcode: 1996IAUC.6345....1W
Altcode:
M. Womack, Pennsylvania State University; M. C. Festou, Observatoire
Midi Pyrenees, Toulouse; and S. A. Stern, Southwest Research Institute,
report observations of comet C/1996 B2 with the National Radio Astronomy
Observatory's 12-m telescope at Kitt Peak: "The following lines were
detected during Mar. 16 and 17: H2CO 3(12)-2(11) at 226 GHz, HCN
3-2 at 266 GHz, CO 2-1 at 230 GHz and CH3OH at 145 GHz. Based on the
detected brightness temperatures and an assumed rotational temperature
of 50 K we estimate production rates of Q(H2CO) = 2*10**26/s, Q(CO) =
3*10**28/s, Q(CH3OH) = 5*10**26/s and Q(HCN) = 3*10**26/s. This Q(HCN)
is close to that found for CN by R. Millis and D. Schleicher on Mar. 19
(IAUC 6344), suggesting a direct link between the two species. However,
the CO and H2CO data indicate that H2CO is not the main parent of the
observed CO. Interpolation between the present observations of CO and
those reported on IAUC 6335 (and on the assumption that the fluorescence
efficiencies of the millimeter lines have not significantly changed)
indicates a very rapid change in the production rates, presumably near
an r**-5 law, during the last two weeks. If the CO/H2O ratio is 20
percent, as suggested on IAUC 6335, the water production is in excess
of 10**29/s." Improved orbital elements and a detailed new ephemeris
are given on MPEC 1996-F03. The following elements are from the same
solution but for a more current osculation epoch: Epoch = 1996 Mar. 18.0
TT T = 1996 May 1.3966 TT Peri. = 130.2016 e = 0.999705 Node = 188.0432
2000.0 q = 0.230085 AU Incl. = 124.9106 The earlier indication (IAUC
6329) that the comet is not "new" is confirmed, the last perihelion
passage having occurred some 9000 years ago. Corrections to the IAUC
6330 ephemeris: Mar. 22, Delta alpha = -0.01 timemin, Delta delta =
+3.5 arcmin; 23, -0.02, +5.2; 24, -0.04, +7.2; 25, -0.09, +9.0; 26,
-0.4, +9.0; 27, -7, +3.3; 28, -0.7, -5.8; 29, -0.19, -4.7; 30, -0.10,
-3.6; 31, -0.06, -2.8; Apr. 1, -0.04, -2.4; 2, -0.04, -2.0; then to the
IAUC 6311 ephemeris: Apr. 2, -0.08, -4.4; 7, -0.05, -2.3; 12, -0.04,
-1.7; 17, -0.05, -1.4; 22, -0.06, -1.4; 27, -0.08, -1.7. Naked-eye
magnitude estimates: Mar. 20.07 UT, 1.9 (B. H. Granslo, Fjellhamar,
Norway); 20.09, 2.3 (K. Cernis, Lavariskes, Lithuania); 20.58, 2.5
(S. O'Meara, Volcano, HI); 20.98, 2.1 (P. Pravec, Ondrejov, Czech
Republic); 21.16, 2.2 (B. G. Marsden, Lexington, MA); 21.31, 1.6
(J. V. Scotti, Tucson, AZ); 21.48, 1.3 (C. S. Morris, near Gorman, CA).
Title: Comet C/1996 B2 (Hyakutake)
Authors: Schleicher, D.; Millis, R.; Festou, M.; Andernach, H.;
A'Hearn, M.; Haken, M.; Moreels, G.; Clairemidi, J.
Bibcode: 1996IAUC.6333....1S
Altcode:
D. Schleicher, Lowell Observatory, communicates: "Narrow-band photometry
of C/1996 B2 was obtained by R. Millis and myself using the Hall
1.07-m and the 0.79-m telescopes at Lowell Observatory on Feb. 25.5
(r = 1.60 AU) and Mar. 1.5 UT (r = 1.51 AU), respectively. Haser-model
production rates for the two dates, respectively, were: log Q(OH) =
28.68 and 28.73, log Q(CN) = 26.08 and 26.15, and log Q(C2) = 26.22
and 26.32. The dust production rates were log [Af(rho)] = 3.38 and
3.45. Combining these results with those previously obtained on
Feb. 9.5 at r = 1.90 AU (cf. IAUC 6311) implies that the OH- and
CN-production rates are essentially unchanged over the three-week
time span, while C2 increased by 50 percent and dust production has
increased by about 80 percent. Therefore, while the water-production
r dependence is apparently flat, the species primarily responsible
for naked-eye visibility currently exhibit a production-rate slope
of about -2. This assumes that any short-term variations are not
distorting the true r dependence, an assumption consistent with recent
IUE observations (see below). M. Festou, H. Andernach, M. A'Hearn,
M. Haken, G. Moreels, and J. Clairemidi report for the International
Ultraviolet Explorer (IUE) ToO Team the following observations of
C/1996 B2 made at VILSPA on Feb. 19.3 (r = 1.71 AU), 22.2 (1.66),
and 27.2 UT (1.57): "The production of both water and dust shows
no change over the interval. Using the same Haser model as that of
Schleicher and Millis (see above), log Q(OH) = 28.68, 28.68, and 28.64,
in remarkably good agreement with their results. For a 'best' vectorial
model, the corresponding values of Q would be a bit more than 2 times
larger. The dust production at 300-304 nm can be characterized by
log Af(rho) = 3.17, 3.17, and 3.18 (cf. A'Hearn et al. 1984, AJ 89,
579). These values are not directly comparable with the values found
by Schleicher and Millis above, since they are measured at a different
wavelength. Taken together, they suggest that the dust has changed
from neutral in color to reddish. CS is also approximately constant
over the interval. This complete lack of brightening as the comet
approaches the sun is just the behavior that might have been expected
for a dynamically new comet, although the latest orbital solutions
(Marsden, IAUC 6329) suggest that the comet is not dynamically new."
Title: Dynamics of the Solar Granulation: Its Interaction with the
Magnetic Field
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 1996mpsa.conf..617N
Altcode: 1996IAUCo.153..617N
No abstract at ADS
Title: Evidence of shear flows in the solar granulation
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 1996ASPC..109..143N
Altcode: 1996csss....9..143N
No abstract at ADS
Title: Comet 1995 O1
Authors: Abe, H.; Nakano, S.; Ticha, J.; Tichy, M.; Pettarin, E.;
Toso, A.; Schleicher, D. G.; Spahr, T. B.; Yoshida, S.
Bibcode: 1995IAUC.6189....1A
Altcode:
The following additional precise positions have been reported: 1995 UT
R.A. (2000) Decl. m1 Observer July 24.59517 18 43 06.68 -32 08 28.5 Abe
24.60142 18 43 06.47 -32 08 27.6 " 24.85549 18 42 55.65 -32 08 03.7 12
Ticha 24.85676 18 42 55.61 -32 08 03.0 " 24.85757 18 42 55.60 -32 08
03.2 " 24.85836 18 42 55.54 -32 08 03.4 " 24.85919 18 42 55.50 -32 08
03.0 " 24.87581 18 42 54.81 -32 08 00.6 Pettarin 24.93351 18 42 52.37
-32 07 55.9 " 25.23715 18 42 39.13 -32 07 25.0 Schleicher 25.24229 18
42 38.92 -32 07 24.8 " 25.24516 18 42 38.82 -32 07 24.7 " 25.52113 18 42
27.45 -32 06 58.5 Yoshida 25.52545 18 42 27.26 -32 06 57.9 " 25.52975 18
42 27.07 -32 06 58.0 11.6 " H. Abe (Yatsuka). 0.26-m f/4.8 reflector +
CCD. Communicated by S. Nakano, Sumoto, Japan. J. Ticha and M. Tichy
(Klet). 0.57-m f/5.2 reflector + CCD. E. Pettarin and A. Toso (Farra
d'Isonzo). 0.4-m f/4.5 reflector + CCD. D. G. Schleicher and T. B. Spahr
(Anderson Mesa Station, Lowell Observatory). 1.1-m f/8 Hall reflector +
CCD. S. Yoshida (Wakayama). 0.25-m f/6.3 Schmidt-Cassegrain reflector +
CCD. Communicated by Nakano.
Title: Self-Organization of Magnetic and Velocity Fields in Solar
Intergranules
Authors: Nesis, A.; Hammer, R.; Schleicher, H.
Bibcode: 1995SPD....26..504N
Altcode: 1995BAAS...27..957N
No abstract at ADS
Title: Comet 6P/d'Arrest
Authors: Wasserman, L. H.; Millis, R. L.; Schleicher, D. G.
Bibcode: 1995IAUC.6140....4W
Altcode:
CCD observations (no flat fielding) by L. H. Wasserman, R. L. Millis
and D. G. Schleicher with the 1.1-m Hall telescope at the Lowell
Observatory: Feb. 2.53 UT, R = 21.5, I = 21.9; 3.50, I = 23.
Title: Observation at 892 nm of impact "L" with the solar Vacuum
Tower Telescope at Tenerife.
Authors: Schleicher, H.; Balthasar, H.; Jockers, K.; Knölker, M.;
Schmidt, W.
Bibcode: 1995ESOC...52..171S
Altcode: 1995eslj.work..171S; 1995esl9.conf..171S
During the period of SL-9 impacting Jupiter, the authors observed
Jupiter with the solar VTT. The impact of fragment "L" was monitored
with a time series of filtergrams in the CH4-band at 892 nm.
Title: Two-dimensional spectroscopy of a sunspot.
Authors: Balthasar, H.; Schleicher, H.; Bendlin, C.; Volkmer, R.
Bibcode: 1995AGAb...11..143B
Altcode:
No abstract at ADS
Title: Sunspot limb distance variations measured simultaneously with
two telescopes.
Authors: Berger, B.; Balthasar, H.; Schleicher, H.; Wöhl, H.;
Wiehr, E.
Bibcode: 1995AGAb...11..142B
Altcode:
No abstract at ADS
Title: Impact L observed at a wavelength of 892 nm with the solar
vacuum telescope on Tenerife
Authors: Schleicher, H.; Balthasar, H.; Knölker, M.; Schmidt, W.;
Jockers, K.
Bibcode: 1995HiA....10..632S
Altcode:
No abstract at ADS
Title: Observations at 891 nm of the impact "L" of SL-9 on Jupiter.
Authors: Balthasar, H.; Jockers, K.; Knölker, M.; Schleicher, H.;
Schmidt, W.
Bibcode: 1994AGAb...10..122B
Altcode:
No abstract at ADS
Title: The Impact of Fragment ``L'' of Comet SL-9 on Jupiter
Authors: Schleicher, H.; Balthasar, H.; Knolker, M.; Schmidt, W.;
Jockers, K.
Bibcode: 1994EM&P...66...13S
Altcode:
Filtergrams of high spatial and temporal resolution were obtained in
the methane band centred at 892 nm during the impact of fragment L of
comet Shoemaker-Levy 9 on Jupiter. The light curve shows two maxima of
an emission ball observed above the limb shortly after the impact. The
second maximum was the brightest and had a short life time of about 90
seconds. During it's life, the apparent height of the emission ball
declined towards the surface of Jupiter; the amount of displacement
is larger than the expected effect caused by Jupiter's rotation. About
half an hour after the impact, a domelike feature became visible when
the location of the impact rotated into the illuminated hemisphere
of Jupiter.
Title: Time saeries of the penumbral Evershed effect.
Authors: Schleicher, H.; Wiehr, E.; Balthasar, H.; Wöhl, H.
Bibcode: 1994AGAb...10..113S
Altcode:
No abstract at ADS
Title: Doppler oscillations in solar prominences simultaneously
observed with two telescopes. Discovery of a 30 S oscillation
Authors: Balthasar, H.; Wiehr, E.; Schleicher, H.; Wohl, H.
Bibcode: 1993A&A...277..635B
Altcode:
Time series of Doppler shifts are observed simultaneously with two
telescopes in order to separate actual solar velocities from influences
of image motion or unperfect guiding. Several maxima of the power
contours occur only in the data set from one of the two telescopes
and may thus originate from non-solar sources. Considering only those
power maxima which are observed with both telescopes we establish the
solar origin of periods near 20 and 12 min, which may be identified
with `hybrid fast modes' from model calculations. For one prominence a
significant period of 30 5 is detected which theory predicts as a wave
guided by the prominence fine-structures. Our prominence oscillations
are restricted to spatially small areas of a few arc see diameter.
Title: Observational Constraints on the Lifetime of Cometary H
2O
Authors: Cochran, Anita L.; Schleicher, David G.
Bibcode: 1993Icar..105..235C
Altcode:
We used a carefully selected set of observations of five comets along
with a vectorial model and the Haser model to explore the lifetimes
against photodissociation of H2O and OH in cometary
comae. The photometric and long-slit CCD data described in this paper
were obtained specifically for this project, while the IUE data are
archival. The underlying parameter space was examined and our knowledge
of such factors as the outflow and ejection velocities is discussed. We
conclude that it is difficult to constrain the lifetime of OH but that
the H2O lifetimes must be dependent on changes in the solar
UV flux. Our data are consistent with the expectation that as the solar
activity, and thus UV flux, increases, the H2O lifetimes
decrease. From our data, we show that the combined theoretical
lifetimes for H2O and OH do not produce good fits to
the data; thus, at least one set of theoretical lifetimes must be in
error. Our data require shorter H2O lifetimes and/or shorter
OH lifetimes. We present some useful relations for determining which
lifetimes and velocities to use for future applications. Additionally,
we have derived improved lifetimes and scale lengths for use computing
production rates with simple models. The new parent lifetimes and scale
lengths are about 15-45% shorter than commonly used values which ignore
effects due to solar activity. Finally, we discuss what data types
are needed in the future to enable better modeling of cometary data.
Title: Periodic Comet Swift-Tuttle (1992t)
Authors: McFadden, L.; Schleicher, D.; Schultz, R.; Chamberlin, A.;
A'Hearn, M.; Feldman, P.; Haken, M.; McPhate, J.; Mikuz, H.; Boattini,
A.; Midtskogen, O.; Vanmunster, T.; Kereszturi, A.; Green, D. W. E.;
Dahle, H.; Ohkuma, M.; Behrend, R.; Morris, C. S.
Bibcode: 1992IAUC.5663....1M
Altcode:
L. McFadden, University of Maryland, reports that spectroscopic
observations (range 380-525 nm) of P/Swift-Tuttle made on Oct. 5.097 UT
by D. Schleicher, R. Schultz, A. Chamberlin, and herself with the 1.8-m
Perkins Telescope at Lowell Observatory (+ Ohio State CCD spectrograph)
yield the following production rates, following a preliminary
reduction by Schultz: log Q(CN) = 26.77, log Q(C3) = 25.72, log Q(C2) =
26.49. M. A'Hearn, University of Maryland, communicates: "Observations
of P/Swift-Tuttle by L. McFadden, P. Feldman, M. Haken, J. McPhate, and
myself using the International Ultraviolet Explorer yield the following
respective water production rates (standard vectorial model, in units of
10**29 molecules/s): Nov. 3.1 UT, 1.5; 3.9, 2.2; 4.4, 2.5; 16.0, 3.4;
23.9 approx. 5. CS production is roughly 0.2 percent, as in P/Halley,
but higher than in most comets. Relative abundance can be significantly
affected by phase lags during variability. The continuum brightness
implies a gas-to-dust ratio comparable to but slightly higher than
that of P/Halley. Photometric variability during the shifts indicates
that periodic variations must have periods considerably greater than
16 hr." H. Mikuz, Ljubljana, Slovenia, reports that several 10-min CCD
frames obtained around Nov. 19.78 and 20.75 UT, with a 250-mm f/4 lens
and an H2O+ 620-nm filter, show a straight ion tail about 4.5 deg long
in p.a. 41 deg. Similar frames on Nov. 23.73-23.77 show a straight
ion tail about 6.7 deg long in p.a. 44 deg, when a red continuum
filter (647 nm) showed a fan of dust about 2 deg long extending in
p.a. 10-40 deg. Both filters have FWHM = 10 nm. Clouds and knots of
material are present along the tail stream on all three nights. Further
total visual magnitude estimates: Nov. 14.75 UT, 5.0 (A. Boattini,
Piazzano, Italy, naked eye); 15.70, 5.3 (O. Midtskogen, Tranby,
Norway, 0.05-m refractor); 17.78, 4.9 (T. Vanmunster, Landen, Belgium,
0.12-m reflector); 18.69, 5.0 (A. Kereszturi, Budapest, Hungary, 20
x 60 binoculars); 20.95, 4.9 (D. W. E. Green, Cambridge, MA, 12 x 50
binoculars); 21.69, 5.5 (H. Dahle, Oslo, Norway, 7 x 50 binoculars);
22.38, 4.6 (M. Ohkuma, Mt. Fuji, Japan, 10 x 70 binoculars); 23.74,
5.4 (R. Behrend, La Chaux-de-Fonds, Switzerland, 10 x 40 binoculars);
25.11, 5.0 (C. S. Morris, La Canada, CA, 10 x 50 binoculars).
Title: Time series of Doppler velocities in prominences.
Authors: Balthasar, H.; Schleicher, H.; Wöhl, H.; Wiehr, E.
Bibcode: 1992AGAb....7..151B
Altcode:
No abstract at ADS
Title: Standard stars for photometry of comets
Authors: Osborn, Wayne H.; A'Hearn, Michael F.; Carsenty, Uri;
Millis, Robert L.; Schleicher, David G.; Birch, P. V.; Moreno, H.;
Gutierrez-Moreno, A.
Bibcode: 1990Icar...88..228O
Altcode:
A set of standard stars for photometric observations of comets
has been established. Magnitudes for 63 stars in 10 bandpasses are
presented. The bandpasses are those of the nine filters recommended by
the International Astronomical Union for comet photometry, which measure
the C 2, C 3, CN, CO +, H 2O
+ and OH emission and three continuum points, plus a 10th
filter which measures NH emission. The stars observed include those
recommended by the International Halley Watch for use in photometric
observations of Comet Halley during the 1985-1986 apparition.
Title: Absolute age determination. Physical and chemical dating
methods and their application.
Authors: Geyh, M. A.; Schleicher, H.
Bibcode: 1990aadp.book.....G
Altcode:
The spectrum of physical and chemical dating methods now covers
the entire range of Earth history. But there are so many methods
that it is becoming increasingly difficult to select those that are
appropriate for solving a specific problem. The objective of this
book is to cover the whole spectrum of methods and to give examples
of their applications. Contents: 1. Introduction. 2. Time scales
and ages. 3. Selection, collection, packing, storage, transport,
and description of the samples. 4. Treatment and interpretation
of the raw data. 5. Physical dating methods. 6. Radiometric
dating methods. 7. Chronostratigraphic methods using global
time markers. 8. Chemical dating methods. 9. Phanerozoic
time-scale. 10. Literature.
Title: The Nucleus of Comet P/Tempel 2
Authors: A'Hearn, Michael F.; Campins, Humberto; Schleicher, David G.;
Millis, Robert L.
Bibcode: 1989ApJ...347.1155A
Altcode:
Simultaneous optical photometry and IR radiometry of Comet P/Tempel
2 are presented. Periodic variations of brightness are present and in
phase at all wavelengths. Because the optical and thermal rotational
light curves are in phase, it is concluded that the variations are
caused by the changing apparent cross section of an elongated nucleus
rotating with a period near 8.9 h. The variation of flux with aperture
makes it possible to separate the contributions of the nucleus and
the coma. The contribution by the coma is about 25 percent at maximum
light in the optical and undetectable at the level of 10 percent at
all times in the thermal IR.
Title: Periodic Comet Brorsen-Metcalf (1989o)
Authors: Schleicher, D. G.; Osip, D. J.; Millis, R. L.; Wagner, R. M.;
Bertram, R.; Beaver, J.; Lutz, B. L.; Spinrad, H.; Dickinson, M.; Dey,
R.; Morris, C. S.; Seargent, D. A. J.; Green, D. W. E.; Bortle, J. E.
Bibcode: 1989IAUC.4810....1S
Altcode:
D. G. Schleicher, D. J. Osip, and R. L. Millis, Lowell Observatory,
communicate: "We report gas production rates from aperture photometry
obtained on July 7.43 UT, using the Lowell 1.07-m telescope: log Q(OH)
= 27.8, log Q(CN) = 25.4, log Q(C2) = 25.3, log Q(C3) = 24.2, log Q(NH)
= 25.0. The gas-to-dust ratio is high, with log Q(OH)/(A f rho) = 26.2
(cf. A'Hearn et al. 1984, A.J. 89, 579). Continuum magnitude at 485 nm
within a 75"- diameter aperture is about 14.0. The comet is extremely
diffuse, presumably due to the low concentration of dust." R. M. Wagner,
R. Bertram, and J. Beaver, Ohio State University; and D. G. Schleicher
and B. L. Lutz, Lowell Observatory, report: "Long-slit spectra were
obtained on July 7.44 UT using the OSU CCD Spectrograph (spectral range
360-620 nm, resolution 0.8 nm) on the Perkins 1.8-m reflector at Lowell
Observatory. Strong molecular emissions of CN, C3, CH, C2, and NH2 were
present, superposed on a very weak continuum. CN (Delta v=0) and C2
(Delta v=0) emission extended for at least 5' along the projected length
of the slit." H. Spinrad reports that spectra obtained by M. Dickinson,
R. Dey, and himself with the low-resolution spectrograph (range 390-800
nm) on the 3-m Shane reflector at the Lick Observatory on July 7.47 UT
show strong C2 and O I and detectable C3 and CN emission. The continuum
was moderately weak. Total visual magnitude estimates: July 8.45 UT,
9.6 (C. S. Morris, Pine Mountain Club, CA, 20x80 binoculars; 9' coma);
10.76, 9.0 (D. A. J. Seargent, The Entrance, N.S.W., 0.15-m reflector);
12.30, 7.8 (D. W. E. Green, Harvard, MA, 7x50 binoculars; 12' coma);
13.32, 8.1 (J. E. Bortle, Stormville, NY, 10x50 binoculars; 10' coma).
Title: A thinned CCD camera for solar spectroscopic investigations -
testing and first applications
Authors: Schleicher, H.; Wittman, A. D.; Wöhl, H.; Ye, B.
Bibcode: 1989AGAb....3...18S
Altcode:
No abstract at ADS
Title: Periodic Comet Tempel 2 (1987g)
Authors: A'Hearn, M.; Campins, H.; Schleicher, D.
Bibcode: 1988IAUC.4614....3A
Altcode:
M. A'Hearn, H. Campins and D. Schleicher report simultaneous optical
and thermal infrared observations from the University of Hawaii's
2.2-m reflector and Infrared Telescope Facility on Mauna Kea on June
10 and 11. They confirm the basic period (near 9 hours) and amplitude
(near 0.5 mag) of the double-peaked lightcurve of Wisniewski (IAUC
4603). In a 10" aperture the coma contribution was constant at 20
percent of the total light at maximum in the optical and less than
5 percent at 10 microns. The effective nuclear radius at maximum is
5.6 +/- 0.2 km with geometric albedo 0.024 +/- 0.005 and axial ratio
greater than or equal to 1.9.
Title: Ultraviolet spectrophotometry of comet Giacobini-Zinner during
the ICE encounter
Authors: McFadden, L. A.; A'Hearn, M. F.; Feldman, P. D.; Bohnhardt,
H.; Rahe, J.; Festou, M. C.; Brandt, J. C.; Maran, S. P.; Niedner,
M. B.; Smith, A. M.; Schleicher, D. G.
Bibcode: 1987Icar...69..329M
Altcode:
A program of ultraviolet spectrophotometry using the International
Ultraviolet Explorer (IUE) Observatory was carried out in support of
the International Cometary Explorer (ICE) mission. The H 2O
production rate was monitored from 1985 June to October. Between 1985
September 9 and 12, the spatial and temporal variation and abundance
(or upper limits) of the remotely detectable species, C, CO, CO
+, CO 2+, CS, H, Mg +, O,
OH, and S, were obtained. These observations included the time of the
ICE encounter (1985 September 11.46) when the H 2O production
rate was 3 × 10 28 sec -1 ± 50%. This rate is
consistent with a number of gas production rates derived indirectly
from the ICE experiments. The comet was in a nearly steady state
around the time of encounter showing no evidence of short-term temporal
fluctuations in brightness greater than 6%. A sunward-tailward asymmetry
of the OH brightness was observed at 10,000 km from the nucleus. The
absence of detected Mg + rules out this species as a possible
ion of M/Q = 24 which was detected by the Ion Composition Instrument,
part of the ICE complement of instruments. Comparison of the abundance
of CO 2+ ions with total electron density measured
by the plasma electron and radio science experiments on ICE indicates
a deficiency of ions relative to electrons. To satisfy charge balance
criteria, a major population of ions not detected by remote sensing
must be present.
Title: Periodic Comet Halley (1982i)
Authors: Brooke, T. Y.; Knacke, R.; Wehinger, P. A.; Wyckoff, S.;
Foltz, C.; Heller, C.; Wagner, M.; Schleicher, D.; Festou, M.
Bibcode: 1985IAUC.4041....2B
Altcode:
T. Y. Brooke and R. Knacke report magnitudes (7"2 diaphragm) obtained
at the NASA Infrared Telescope Facility on Feb. 17.3 UT: J = 18.53
+/- 0.20, H = 17.76 +/- 0.17, K = 17.82 +/- 0.29. These do not
confirm the very blue color noted on IAUC 4034, and J-H and H-K are
comparable to those of RD objects and other comets. P. A. Wehinger,
Arizona State University, reports: " Reticon spectra (300-750 nm,
1.5 nm resolution) obtained on Feb. 17 with the 4.5-m Multiple-Mirror
Telescope by S. Wyckoff, C. Foltz and C. Heller, in collaboration
with Wehinger, M. Wagner, D. Schleicher and M. Festou, show evidence
for weak CN emission at 387.5 nm. The observed band strength through
a 5" diameter aperture was 1.9 +/- 1.4 x 10**-18 J m**-2 s**-1 after
subtraction of the reflected solar continuum. The average CN column
density centered on the nucleus was 3.3 x 10**13 m**-2, and the CN
production rate calculated from the vectorial model Q = 6 x 10**25
s**-1. When the spectrum of the comet is ratioed with that of a G star,
very marginal evidence is found for the presence of several additional
weak emission features in the 320-700 nm region. The magnitude and color
(measured through the 5" aperture) were V = 18.9, B-V = +0.66. No
significant brightness variations > +/- 0.2 mag were observed
in twelve successive 10-min integrations during 3.5 hr beginning on
Feb. 17.12 UT."
Title: Periodic Comet Halley (1982i)
Authors: Belton, M.; Spinrad, H.; Wehinger, P.; Wyckoff, S.; Wagner,
M.; Schleicher, D.; Morris, C.; Hale, A.; Valisa, P.
Bibcode: 1985IAUC.4029....1B
Altcode:
Low-resolution spectra (~ 1.5 nm) of P/Halley were obtained by 2
groups in Arizona using the Kitt Peak 4-m telescope with the cryogenic
camera (spectral range = 460-800 nm; observers M. Belton, H. Spinrad,
P. Wehinger, S. Wyckoff) and the Mount Hopkins 4.5-m MMT with an
intensified reticon (range 300-750 nm; observers Wyckoff, Wehinger,
Belton, M. Wagner, D. Schleicher). The Kitt Peak group observed on
1984 Feb. 4 UT (V = 23.5, exposure time 3600 s), Oct. 30 (V = 21.3,
5800 s), and Nov. 26 (V = 20.5, 3600 s), while the MMT group observed
on 1984 Nov. 26 (V = 20.5, 4000 s). The data show no detected molecular
or atomic emission features, but only a reflected solar continuum. The
Nov. 26 Kitt Peak spectra probably indicate an albedo increase by ~
30 percent over the range 460-800 nm relative to earlier spectra. The
Oct. 30 data (obtained with a long slit) show a resolved/extended coma
~ 16" in diameter (5.5 x 10**4 km) in the sunward direction. Belton,
Spinrad, Wehinger, and Wyckoff also report that observations made on
1984 Dec. 27 UT, with the Kitt Peak 4-m reflector and cryogenic camera
(TI 800x800-pixel CCD; spectral resolution 1.5 nm), show continuous
spectra for both 1983 TB and comet 1984s, except the latter did show
weak [O I] 630-nm emission which extended 4"-5" into the coma. The
long-slit spectra (4') of the comet also show broad wings (50") in
the continuum which are significantly redder than the central part
of the coma. The color of 1983 TB is like an S-type asteroid. Visual
magnitude estimates for 1983 TB: 1984 Dec. 23.14 UT, 13.5: (C. Morris,
Whitaker Peak, CA); 24.23, 13.5 (A. Hale, Pine Valley, CA). Total visual
magnitude estimates of comet 1984s: Dec. 19.88, 10.0 (P. Valisa, Varese,
Italy, 0.20-m reflector; photographic tail 10' to west); 23.19, 10.7
(C. S. Morris, 0.25-m reflector, Whitaker Peak, CA); 1985 Jan. 16.24,
10.3 (Morris, 3' tail in p.a. 40 ). estimates by C. Morris, 0.25-m
reflector, near Mt. Wilson, CA: Jan. 18.56 UT, 13.0; 20.55, 13.0.
Title: Jet activity in the Seyfert galaxy MKN 335
Authors: Fricke, K. J.; Kollatschny, W.; Schleicher, H.
Bibcode: 1983MitAG..58..105F
Altcode:
On prime focus plates of the radio-quiet Seyfert 1 galaxy Mkn 335 the
authors find a jet-like feature to the north west. The line spectrum
of this feature is redshifted with respect to the nucleus and shows
line ratios different from those in the nuclear spectrum.
Title: Extranuclear activity in MKN 335
Authors: Fricke, K. J.; Kollatschny, W.; Schleicher, H.
Bibcode: 1983ASSL..103..149F
Altcode: 1983ajet.proc..149F
It is believed that the line spectrum of the NW-feature showing emission
line widths comparable to those in the nuclear spectrum may derive
from a secondary weak Seyfert nucleus located in the outskirts of
Mkn 335 as a result of merging or ejection. The bulk velocity of the
feature relative to the nucleus of Mkn 335 of approximately 300 km/s
would be in accord with both options. Merging is thought unlikely for
two reasons. The first is that Mkn 335 is not in a group or cluster;
the second is that there is little sign of galactic material in the
vicinity of the NW-feature. The steep Balmer decrement could be an
indication that dust associated with such material does not belong to
Mkn 335. The possible velocity spread within the emission lines favors
a physical connection of the underlying object with Mkn 335 and its
origin by ejection from the nucleus. The steep Balmer decrement could
then be a consequence of obscuration by dust within Mkn 335. Another
possibility is that the broad and narrow emission lines originate from
a gaseous jet and its confining dense surroundings.
Title: The line spectrum of the Fe II Seyfert I galaxy AKN 120
Authors: Kollatschny, W.; Schleicher, H.; Fricke, K. J.; Yorke, H. W.
Bibcode: 1981A&A...104..198K
Altcode:
Combined UV and optical spectra are presented for the Fe II Seyfert
galaxy Akn 120. The galaxy shows unusually strong Ly-alpha and UV Fe
II emission, as well as a jump in the continuum at 3000-4000 A. The
spectra are obtained with the IUE satellite telescope in both the short
and long wavelength regions. Also discussed is an optical spectrum
which has been taken nearly simulataneously with the UV spectra,
thereby avoiding the effects of a possible variability of Akn 120.
Title: Variability of the continuum and the emission lines in the
Seyfert 1 galaxy Akn 120.
Authors: Kollatschny, W.; Fricke, K. J.; Schleicher, H.; Yorke, H. W.
Bibcode: 1981A&A...102L..23K
Altcode:
No abstract at ADS
Title: UV observations of the BL Lac object 0716+71.
Authors: Fricke, K. J.; Kollatschny, W.; Schleicher, H.
Bibcode: 1981A&A...100....1F
Altcode:
UV observations acquired by the IUE satellite of the BL Lac object
0716+71 are presented. Data were obtained in both the long- and
short-wavelength ranges (2400-3000 and 1250-1900 A) and reduced using
the spatially resolved line by line spectrum and the geometrically and
photometrically corrected image in view of the very low signal-to-noise
ratio. Integrated fluxes of 6.4 + or - 0.5 and 2.9 + or - 0.4 x 10
to the -13th erg/sec per sq cm are measured for the 1300-1900 and
2400-3000A ranges, respectively, using the corrected image, and 8.6 +
or - 0.8 and 3.7 + or - 0.5 x 10 to the -13th erg/sec per sq cm using
the line by line spectrum. Data are consistent with an overall power
law spectrum with an index of -1 from the mm to the X-ray region and
a pronounced excess in the near IR and optical regions.
Title: Observations of six flat spectrum sources from the 5 GHz
survey.
Authors: Biermann, P.; Duerbeck, H.; Eckart, A.; Fricke, K.; Johnston,
K. J.; Kuhr, H.; Liebert, J.; Pauliny-Toth, I. I. K.; Schleicher,
H.; Stockman, H.; Strittmatter, P. A.; Witzel, A.
Bibcode: 1981ApJ...247L..53B
Altcode:
Observations at radio, optical, and X-ray wavelengths of six sources
from the Bonn-NRAO 5 GHz survey are reported. The sources were
selected on the basis of their flux densities and spectral indices at
5 GHz. All have been shown to contain compact radio cores and to emit
strongly at X-ray wavelengths; five are strongly polarized at optical
wavelengths. The measured flux densities suggest that the sources are
of comparable luminosity (per fractional bandwidth) in the X-ray and
optical regions. The interpretation of these results in terms of a
synchrotron-self-Compton mechanism is briefly discussed.
Title: Photoelectric scanner measurements of Balmer emission line
profiles for southern Be stars. II. A survey for variations.
Authors: Dachs, J.; Eichendorf, W.; Schleicher, H.; Schmidt-Kaler,
T.; Stift, M.; Tug, H.
Bibcode: 1981A&AS...43..427D
Altcode:
Between 1974 and 1979, more than 800 Hα, Hβ and Hγ line profiles were
measured for 36 bright southern Be and B-type shell stars as well as
for three early-type supergiants (β Ori, ζ Pup, and ζ1
Sco) and for four B-type comparison stars having Balmer lines in
absorption. For the measurements, a photoelectric spectrum scanner was
used giving a nominal spectral resolution of about 2 Å at Hα and of
1 Å for the other lines. The program includes most of the southern
Be stars reported to have Balmer line emission strength of at least
e2 in the notation of Lesh (1968). An atlas of about 200
Balmer line profiles is presented containing a selection of typical
profiles for the program stars. It demonstrates the variety of profiles
as well as the presence of short-and long-term variations. For a few
stars, the measurements could be supplemented by photographic coudé
spectrograms. The following main results and conclusions drawn
from our data are: 1. If the strength of Balmer line emission
according to MK classification spectrograms is at least e2
for a Be star, the equivalent widths of its Hα and Hβ emission
lines exceed about -30 Å and -2.4 Å respectively. 2. Between
1974 and 1977, Balmer line emission disappeared in the spectrum of
μ Cen, but reappeared for α Eri. 3. HR 2790 (= HD 57219) and
HR 4618 (= HD 105382) should be deleted from Be star catalogues. 4. Projected stellar rotational velocities are determined for five
Be stars for which they were not previously known. HR 5223 (= HD
120991) was detected to be a pole-on star showing the Balmer lines up
to H 24 in emission in early-1979. 5. Changes of Hα equivalent
width exceeding ten percent were detected with time scales from a few
nights (two stars) up to several years (three stars). Only three stars
out of 18 for which observations covering three years are available
show Balmer line emission with constant equivalent widths and line
shapes. V/R variations from night to night are visible in the Balmer
emission line profiles of four stars while V/R variations on longer
time scales are very common. 6. For Be stars having single Hα
emission lines without central reversal, the half-width of the Hα
emission line is usually less than the projected rotational velocity
of the central star in the Hα emitting envelope. In a few cases,
Hα line broadening is variable in time. 7. Strong persistent
asymmetry of Hα emission lines probably indicates permanent radial
motions in the envelopes of several Be stars. 8. For six Be stars
and for the three supergiants included in the survey, faint wings of
Hα emission are detected extending to about 20 to 30 Å from the line
centres. Possible origins of these extended wings might be electron
scattering or a stellar wind.
Title: IUE Observations of a new BL Lac Object from the S5 Radio
Catalogue
Authors: Fricke, K. J.; Kollatschny, W.; Schleicher, H.; Yorke, H. W.
Bibcode: 1981MitAG..52...61F
Altcode:
No abstract at ADS
Title: Optical and Ultraviolet Spectra of Seyfert Galaxies
Authors: Fricke, K. J.; Kollatschny, W.; Schleicher, H.; Yorke, H. W.
Bibcode: 1981MitAG..52...62F
Altcode:
No abstract at ADS
Title: Optical and ultraviolet spectra of Seyfert galaxies
Authors: Fricke, K. J.; Kollatschny, W.; Schleicher, H.; Yorke, H. W.
Bibcode: 1981AGAb...52...62F
Altcode:
Using the IUE satellite, low resolution UV spectra from the Seyfert
galaxies NGC 1566, NGC 7603, Akn 120, and Mkn 3 were obtained. The first
two objects were observed only in the short wavelength region 1100 -
2000 A, the other two also in the long wavelength region 2000 - 3000
A. The IDS spectra were reduced using the standard ESO software. Both
the optical and UV spectra were corrected for interstellar extinction
in our galaxy and EB-V values were derived from 21 cm maps.
Title: IUE observations of a new BL lac object from the S5 radio
catalogue
Authors: Fricke, K. J.; Kollatschny, W.; Schleicher, H.; Yorke, H. W.
Bibcode: 1981AGAb...52...61F
Altcode:
Low resolution UV spectra of Kuhr A were obtained in the wavelength
regions 2000-3000 A and 2000-1100 A. The detection limit for emission
lines was estimated to be approx. equally to 10 to the minus 13th
power erg/sec/sq cm.
Title: Spectroscopy of Seyfert Galaxies
Authors: Schleicher, H.
Bibcode: 1981goje.symp...89S
Altcode:
No abstract at ADS
Title: Photoelectric scanner measurements of Balmer emission line
profiles for southern Be stars. II. A survey for variations.
Authors: Dachs, J.; Eichendorf, W.; Schleicher, H.; Schmidt-Kaler,
T.; Stift, M.; Tüg, H.
Bibcode: 1981BeSN....3....2D
Altcode:
No abstract at ADS
Title: Optical and Ultraviolet Spectroscopy of the Nuclei of Seyfert
Galaxies
Authors: Schleicher, H.; Yorke, H. W.
Bibcode: 1980Msngr..22...14S
Altcode:
The launching of the International Ultraviolet Explorer (IUE) in
1978 has made the ultraviolet sky in the wavelength region from
1150 A to 3200 A accessible to detailed spectroscopic study. The
IUE is a satellite in a geosynchronous orbit, equipped with a 45 cm
telescope with two spectrographs. For a more detailed description of
this satellite, the interested reader is referred to the article by
A. Heck et al. (Messenger No. 15, Oec. 1978). Although the diameter
of the IUE telescope is quite small-its size is more typical of an
amateur telescope than of a scientific instrument-it has been used
successfully even for extragalactic spectroscopy.
Title: IUE observations of Seyfert galaxies and a BL Lac object.
Authors: Schleicher, H.; Fricke, K. J.; Kollatschny, W.
Bibcode: 1980ESASP.157..271S
Altcode: 1980IUE2E.R....271S; 1980iue..conf..271S; 1980IUE2n......271S
Spectrophotometric data for Seyfert galaxies NGC 1566, NGC7603, Akn
120, and Mkn 3, and the BL Lac object 0716 + 71 were taken. Spectra
in short and long wavelength regions corrected for galactic reddening
are presented as well as absolute emission line intensities.
Title: UV Spectroscopy of Very Bright Suspected BL Lac Objects
Authors: Schleicher, H.
Bibcode: 1980iue..prop..589S
Altcode:
No abstract at ADS
Title: Ein empirisches Modell für die tiefen Umbra-Schichten
Authors: Wiehr, E.; Stellmacher, G.; Schleicher, H.
Bibcode: 1976MitAG..38..217W
Altcode:
No abstract at ADS