Author name code: nelson-chris ADS astronomy entries on 2022-09-14 author:"Nelson, Christopher J." OR "Nelson, Chris J." ------------------------------------------------------------------------ Title: IRIS burst properties in active regions Authors: Nelson, C. J.; Kleint, L. Bibcode: 2022arXiv220811013N Altcode: Interface Region Imaging Spectrograph (IRIS) bursts are localised features thought to be driven by magnetic reconnection. Although these events are well-studied, it remains unknown whether their properties vary as their host active regions (ARs) evolve. Here, we aim to understand whether the measurable properties of IRIS bursts are consistent during the evolution of their host ARs. We study 42 dense 400-step rasters sampled by IRIS. These rasters each covered one of seven ARs, with each AR being sampled at least four times over a minimum of 48 hours. An automated detection algorithm is used to identify IRIS burst profiles. Data from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager are also used to provide context about the co-spatial line-of-sight magnetic field. Of the rasters studied, 36 were found to contain IRIS burst profiles. Five ARs (11850, 11909, 11916, 12104, and 12139) contained IRIS burst profiles in each raster that sampled them whilst one AR (11871) was found to contain no such spectra at any time. A total of 4019 IRIS burst profiles belonging to 752 connected objects, which we define as parent IRIS bursts, were identified. IRIS burst profiles were only detected within compact regions in each raster, with these regions appearing to increase in size as the host ARs aged. No systematic changes in the frequency of IRIS burst profiles or the spectral characteristic of IRIS burst profiles through time were found for these ARs. Finally, 93 % of parent IRIS bursts with areas between 1 arcsec^2 and 4 arcsec^2 occurred co-spatial to bi-poles in the photosphere. Overall, IRIS bursts have remarkably consistent spectral and spatial properties throughout the evolution of ARs. These events predominantly form within the cores of larger and more complex ARs, with the regions containing these events appearing to increase in size as the host region itself evolves. Title: The European Solar Telescope Authors: Quintero Noda, C.; Schlichenmaier, R.; Bellot Rubio, L. R.; Löfdahl, M. G.; Khomenko, E.; Jurcak, J.; Leenaarts, J.; Kuckein, C.; González Manrique, S. J.; Gunar, S.; Nelson, C. J.; de la Cruz Rodríguez, J.; Tziotziou, K.; Tsiropoula, G.; Aulanier, G.; Collados, M.; the EST team Bibcode: 2022arXiv220710905Q Altcode: The European Solar Telescope (EST) is a project aimed at studying the magnetic connectivity of the solar atmosphere, from the deep photosphere to the upper chromosphere. Its design combines the knowledge and expertise gathered by the European solar physics community during the construction and operation of state-of-the-art solar telescopes operating in visible and near-infrared wavelengths: the Swedish 1m Solar Telescope (SST), the German Vacuum Tower Telescope (VTT) and GREGOR, the French Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires (THÉMIS), and the Dutch Open Telescope (DOT). With its 4.2 m primary mirror and an open configuration, EST will become the most powerful European ground-based facility to study the Sun in the coming decades in the visible and near-infrared bands. EST uses the most innovative technological advances: the first adaptive secondary mirror ever used in a solar telescope, a complex multi-conjugate adaptive optics with deformable mirrors that form part of the optical design in a natural way, a polarimetrically compensated telescope design that eliminates the complex temporal variation and wavelength dependence of the telescope Mueller matrix, and an instrument suite containing several (etalon-based) tunable imaging spectropolarimeters and several integral field unit spectropolarimeters. This publication summarises some fundamental science questions that can be addressed with the telescope, together with a complete description of its major subsystems. Title: Polymeric jets throw light on the origin and nature of the forest of solar spicules Authors: Dey, Sahel; Chatterjee, Piyali; Murthy, O. V. S. N.; Korsós, Marianna B.; Liu, Jiajia; Nelson, Christopher J.; Erdélyi, Robertus Bibcode: 2022NatPh..18..595D Altcode: Spicules are plasma jets that are observed in the dynamic interface region between the visible solar surface and the hot corona. At any given time, it is estimated that about 3 million spicules are present on the Sun. We find an intriguing parallel between the simulated spicular forest in a solar-like atmosphere and the numerous jets of polymeric fluids when both are subjected to harmonic forcing. In a radiative magnetohydrodynamic numerical simulation with sub-surface convection, solar global surface oscillations are excited similarly to those harmonic vibrations. The jets thus produced match remarkably well with the forests of spicules detected in observations of the Sun. Taken together, the numerical simulations of the Sun and the laboratory fluid dynamics experiments provide insights into the mechanism underlying the ubiquity of jets. The non-linear focusing of quasi-periodic waves in anisotropic media of magnetized plasma as well as polymeric fluids under gravity is sufficient to generate a forest of jets. Title: Oscillations in the line-of-sight magnetic field strength in a pore observed by the GREGOR Infrared Spectrograph (GRIS) Authors: Nelson, C. J.; Campbell, R. J.; Mathioudakis, M. Bibcode: 2021A&A...654A..50N Altcode: 2021arXiv210710183N Context. Numerous magnetohydrodynamic oscillations have been reported within solar pores over the past few decades, including in line-of-sight (LOS) velocities, intensities, and magnetic field strengths.
Aims: Our aim is to identify whether high-amplitude oscillations in the LOS magnetic field strength can be detected within a pore located in Active Region 12748 and to investigate which physical mechanisms could be responsible for them.
Methods: A solar pore was observed on 1 September 2019 using the GREGOR Infrared Spectrograph instrument for around one hour. Full-Stokes vectors were sampled in a 37 Å window containing the Fe I 15 648.52 Å line (effective Landé g factor of 3). The LOS magnetic field strength was inferred using the strong-field approximation. Additionally, the Stokes Inversion based on Response functions code was used to gain a more complete understanding of the physical properties of the solar atmosphere at the locations of these oscillations.
Results: Oscillations of more than 100 G are observed in the LOS magnetic field in the period window between 600 and 1272 s at three localised (> 1″2) regions. These oscillations have coherence across individual regions, indicating that jitter cannot account for their occurrence. Longer-period amplitude variations, amplitudes over 200 G, are also detected, but they have periods outside of the cone-of-influence. Numerical inversions confirm both oscillations in the LOS magnetic field strength at optical depths of around log τ5000 = −0.5 (potentially caused by compression) and other effects (e.g. changes in the optical depth or the inclination of the magnetic field) may account for these changes.
Conclusions: The oscillations in the separations of the Stokes-V lobes of the 15 648.52 Å line appear to be solar in nature. Future work will be required to understand whether these are truly oscillations in the magnetic field strength at a specific depth in the solar atmosphere or whether other effects are responsible for these signatures. Title: Flare-induced Sunquake Signatures in the Ultraviolet as Observed by the Atmospheric Imaging Assembly Authors: Quinn, Sean; Mathioudakis, Mihalis; Nelson, Christopher J.; Milligan, Ryan O.; Reid, Aaron; Jess, David B. Bibcode: 2021ApJ...920...25Q Altcode: 2021arXiv210505704Q Sunquakes (SQs) have been routinely observed in the solar photosphere, but it is only recently that signatures of these events have been detected in the chromosphere. We investigate whether signatures of SQs are common in ultraviolet (UV) continua that sample the solar plasma several hundred km above where SQs are typically detected. We analyze observations from the Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA) 1600 and 1700 Å passbands, for SQ signatures induced by the flares of Solar Cycle 24. We base our analysis on the 62 SQs detected in the recent statistical study presented by Sharykin & Kosovichev. We find that 9 out of 62 SQ candidates produced a response that is clearly detected in running-difference images from the AIA 1600 and 1700 Å channels. A binary frequency filter with a width of 2 mHz, centered on 6 mHz, was applied to the data. The first signature of each SQ was detected at distances between 5.2 and 25.7 Mm from the associated flare ribbon. Time-distance and regression analysis allowed us to calculate the apparent transverse velocities of the SQs in the UV data sets and found maximum velocities as high as 41 km s-1, 87 Mm away from the SQ source. Our analysis shows that flare-induced SQ signatures can be detected in the SDO/AIA 1600 and 1700 Å passbands, hinting at their presence in the lower chromosphere. There was no apparent correlation between GOES flare classification and the appearance of the SQ at these heights. Title: Temporal evolution of small-scale internetwork magnetic fields in the solar photosphere (Corrigendum) Authors: Campbell, R. J.; Mathioudakis, M.; Collados, M.; Keys, P. H.; Asensio Ramos, A.; Nelson, C. J.; Kuridze, D.; Reid, A. Bibcode: 2021A&A...652C...2C Altcode: No abstract at ADS Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: Temporal evolution of small-scale internetwork magnetic fields in the solar photosphere Authors: Campbell, R. J.; Mathioudakis, M.; Collados, M.; Keys, P. H.; Asensio Ramos, A.; Nelson, C. J.; Kuridze, D.; Reid, A. Bibcode: 2021A&A...647A.182C Altcode: 2021arXiv210200942C Context. While the longitudinal field that dominates in photospheric network regions has been studied extensively, small-scale transverse fields have recently been found to be ubiquitous in the quiet internetwork photosphere and this merits further study. Furthermore, few observations have been able to capture how this field evolves.
Aims: We aim to statistically characterize the magnetic vector in a quiet Sun internetwork region and observe the temporal evolution of specific small-scale magnetic features.
Methods: We present two high spatio-temporal resolution observations that reveal the dynamics of two disk-centre internetwork regions taken by the new GREGOR Infrared Spectrograph Integral Field Unit with the highly magnetically sensitive photospheric Fe I line pair at 15648.52 Å and 15652.87 Å. We record the full Stokes vector and apply inversions with the Stokes inversions based on response functions code to retrieve the parameters characterizing the atmosphere. We consider two inversion schemes: scheme 1 (S1), where a magnetic atmosphere is embedded in a field free medium, and scheme 2 (S2), with two magnetic models and a fixed 30% stray light component.
Results: The magnetic properties produced from S1 inversions returned a median magnetic field strength of 200 and 240 G for the two datasets, respectively. We consider the median transverse (horizontal) component, among pixels with Stokes Q or U, and the median unsigned longitudinal (vertical) component, among pixels with Stokes V, above a noise threshold. We determined the former to be 263 G and 267 G, and the latter to be 131 G and 145 G, for the two datasets, respectively. Finally, we present three regions of interest, tracking the dynamics of small-scale magnetic features. We apply S1 and S2 inversions to specific profiles of interest and find that the latter produces better approximations when there is evidence of mixed polarities. We find patches of linear polarization with magnetic flux density of the order of 130−150 G and find that linear polarization appears preferentially at granule-intergranular lane boundaries. The weak magnetic field appears to be organized in terms of complex `loop-like' structures, with transverse fields often flanked by opposite polarity longitudinal fields. Title: Significance of Cooling Effect On Comprehension of Kink Oscillations of Coronal Loops Authors: Shukhobodskaia, Daria; Shukhobodskiy, Alexander A.; Nelson, Chris J.; Ruderman, Michael S.; Erdélyi, Robert Bibcode: 2021FrASS...7..106S Altcode: Kink oscillations of coronal loops have been widely studied, both observationally and theoretically, over the past few decades. It has been shown that the majority of observed driven coronal loop oscillations appear to damp with either exponential or Gaussian profiles and a range of mechanisms have been proposed to account for this. However, some driven oscillations seem to evolve in manners which cannot be modelled with purely Gaussian or exponential profiles, with amplification of oscillations even being observed on occasions. Recent research has shown that incorporating the combined effects of coronal loop expansion, resonant absorption, and cooling can cause significant deviations from Gaussian and exponential profiles in damping profiles, potentially explaining increases in oscillation amplitude through time in some cases. In this article, we analyse 10 driven kink oscillations in coronal loops to further investigate the ability of expansion and cooling to explain complex damping profiles. Our results do not rely on fitting a periodicity to the oscillations meaning complexities in both temporal (period changes) and spatial (amplitude changes) can be accounted for in an elegant and simple way. Furthermore, this approach could also allow us to infer some important diagnostic information (such as, for example, the density ratio at the loop foot-points) from the oscillation profile alone, without detailed measurements of the loop and without complex numerical methods. Our results imply the existence of correlations between the density ratio at the loop foot-points and the amplitudes and periods of the oscillations. Finally, we compare our results to previous models, namely purely Gaussian and purely exponential damping profiles, through the calculation of chi^2 values, finding the inclusion of cooling can produce better fits in some cases. The current study indicates that thermal evolution should be included in kink-mode oscillation models in the future to help us to better understand oscillations that are not purely Gaussian or exponential. Title: Torsional oscillations within a magnetic pore in the solar photosphere Authors: Stangalini, Marco; Erdélyi, Robertus; Boocock, Callum; Tsiklauri, David; Nelson, Christopher J.; Del Moro, Dario; Berrilli, Francesco; Korsós, Marianna B. Bibcode: 2021NatAs...5..691S Altcode: 2021NatAs.tmp...82S Alfvén waves have proven to be important in a range of physical systems due to their ability to transport non-thermal energy over long distances in a magnetized plasma. This property is of specific interest in solar physics, where the extreme heating of the atmosphere of the Sun remains unexplained. In an inhomogeneous plasma such as a flux tube in the solar atmosphere, they manifest as incompressible torsional perturbations. However, despite evidence in the upper atmosphere, they have not been directly observed in the photosphere. Here, we report the detection of antiphase incompressible torsional oscillations observed in a magnetic pore in the photosphere by the Interferometric Bidimensional Spectropolarimeter. State-of-the-art numerical simulations suggest that a kink mode is a possible excitation mechanism of these waves. The excitation of torsional waves in photospheric magnetic structures can substantially contribute to the energy transport in the solar atmosphere and the acceleration of the solar wind, especially if such signatures will be ubiquitously detected in even smaller structures with the forthcoming next generation of solar telescopes. Title: Power-law energy distributions of small-scale impulsive events on the active Sun: results from IRIS Authors: Vilangot Nhalil, Nived; Nelson, Chris J.; Mathioudakis, Mihalis; Doyle, J. Gerry; Ramsay, Gavin Bibcode: 2020MNRAS.499.1385V Altcode: 2020MNRAS.tmp.2719N; 2020arXiv200903123V Numerous studies have analysed inferred power-law distributions between frequency and energy of impulsive events in the outer solar atmosphere in an attempt to understand the predominant energy supply mechanism in the corona. Here, we apply a burst detection algorithm to high-resolution imaging data obtained by the Interface Region Imaging Spectrograph to further investigate the derived power-law index, γ, of bright impulsive events in the transition region. Applying the algorithm with a constant minimum event lifetime (of either 60 s or 110 s) indicated that the target under investigation, such as Plage and Sunspot, has an influence on the observed power-law index. For regions dominated by sunspots, we always find γ < 2; however, for data sets where the target is a plage region, we often find that γ > 2 in the energy range (~1023, ~1026) erg. Applying the algorithm with a minimum event lifetime of three time-steps indicated that cadence was another important factor, with the highest cadence data sets returning γ > 2 values. The estimated total radiative power obtained for the observed energy distributions is typically 10-25 per cent of what would be required to sustain the corona indicating that impulsive events in this energy range are not sufficient to solve coronal heating. If we were to extend the power-law distribution down to an energy of 1021 erg, and assume parity between radiative energy release and the deposition of thermal energy, then such bursts could provide 25-50 per cent of the required energy to account for the coronal heating problem. Title: Umbral chromospheric fine structure and umbral flashes modelled as one: The corrugated umbra Authors: Henriques, Vasco M. J.; Nelson, Chris J.; Rouppe van der Voort, Luc H. M.; Mathioudakis, Mihalis Bibcode: 2020A&A...642A.215H Altcode: 2020arXiv200805482H Context. The chromosphere of the umbra of sunspots features an assortment of dynamic fine structures that are poorly understood and often studied separately. Small-scale umbral brightenings (SSUBs), umbral microjets, spikes or short dynamic fibrils (SDFs), and umbral dark fibrils are found in any observation of the chromosphere with sufficient spatial resolution performed at the correct umbral flash stage and passband. Understanding these features means understanding the dynamics of the umbral chromosphere.
Aims: We aim to fully understand the dynamics of umbral chromosphere through analysis of the relationships between distinct observed fine features and to produce complete models that explain both spectral profiles and the temporal evolution of the features. We seek to relate such understanding to umbral flashes.
Methods: We studied the spatial and spectral co-evolution of SDFs, SSUBs, and umbral flashes in Ca II 8542 Å spectral profiles. We produced models that generate the spectral profiles for all classes of features using non-local thermodynamic equilibrium radiative transfer with a recent version of the NICOLE inversion code.
Results: We find that both bright SSUBs and dark SDF structures are described with a continuous feature in the parameter space that is distinct from the surroundings even in pixel-by-pixel inversions. We find a phase difference between such features and umbral flashes in both inverted line-of-sight velocities and timing of the brightenings. For umbral flashes themselves we resolve, for the first time in inversion-based semi-empirical modelling, the pre-flash downflows, post-flash upflows, and the counter-flows present during the umbral flash phase. We further present a simple time-dependent cartoon model that explains the dynamics and spectral profiles of both fine structure, dark and bright, and umbral flashes in umbral chromospheres.
Conclusions: The similarity of the profiles between the brightenings and umbral flashes, the pattern of velocities obtained from the inversions, and the phase relationships between the structures all lead us to put forward that all dynamic umbral chromospheric structures observed to this date are a locally delayed or locally early portion of the oscillatory flow pattern that generates flashes, secondary to the steepening large-scale acoustic waves at its source. Essentially, SSUBs are part of the same shock or merely compression front responsible for the spatially larger umbral flash phenomenon, but out of phase with the broader oscillation. Title: Evolution of downflows in the transition region above a sunspot over short time-scales Authors: Nelson, C. J.; Krishna Prasad, S.; Mathioudakis, M. Bibcode: 2020A&A...640A.120N Altcode: 2020arXiv200613617N Context. Downflows with potentially super-sonic velocities have been reported to occur in the transition region above many sunspots; however, how these signatures evolve over short time-scales in both spatial and spectral terms is still unknown and requires further research.
Aims: In this article, we investigate the evolution of downflows detected within spectral lines sampling the transition region on time-scales of the order of minutes and we search for clues as to the formation mechanisms of these features in co-temporal imaging data.
Methods: For the purposes of this article, we used high-resolution spectral and imaging data sampled by the Interface Region Imaging Spectrograph on the 20 and 21 May 2015 to identify and analyse downflows. Additionally, photospheric and coronal imaging data from the Hinode and Solar Dynamics Observatory satellites were studied to provide context about the wider solar atmosphere.
Results: Four downflows were identified and analysed through time. The potential super-sonic components of these downflows had widths of around 2″ and were observed to evolve over time-scales of the order of minutes. The measured apparent downflow velocities were structured both in time and space, with the highest apparent velocities occurring above a bright region detected in Si IV 1400 Å images. Downflows with apparent velocities below the super-sonic threshold that was assumed here were observed to extend a few arcseconds away from the foot-points, suggesting that the potential super-sonic components are linked to larger-scale flows. The electron density and mass flux for these events were found to be within the ranges of 109.6-1010.2 cm-3 and 10-6.81-10-7.48 g cm-2 s-1, respectively. Finally, each downflow formed at the foot-point of thin "fingers", extending out around 3-5″ in Si IV 1400 Å data with smaller widths (< 1″) than the super-sonic downflow components.
Conclusions: Downflows can appear, disappear, and recur within time-scales of less than one hour in sunspots. As the potential super-sonic downflow signatures were detected at the foot-points of both extended fingers in Si IV 1400 SJI data and sub-sonic downflows in Si IV 1394 Å spectra, it is likely that these events are linked to larger-scale flows within structures such as coronal loops. Title: Solar Flare Prediction Using Magnetic Field Diagnostics above the Photosphere Authors: Korsós, M. B.; Georgoulis, M. K.; Gyenge, N.; Bisoi, S. K.; Yu, S.; Poedts, S.; Nelson, C. J.; Liu, J.; Yan, Y.; Erdélyi, R. Bibcode: 2020ApJ...896..119K Altcode: 2020arXiv200512180K In this article, we present the application of the weighted horizontal gradient of magnetic field (WGM) flare prediction method to three-dimensional (3D) extrapolated magnetic configurations of 13 flaring solar active regions (ARs). The main aim is to identify an optimal height range, if any, in the interface region between the photosphere and lower corona, where the flare onset time prediction capability of WGM is best exploited. The optimal height is where flare prediction, by means of the WGM method, is achieved earlier than at the photospheric level. 3D magnetic structures, based on potential and nonlinear force-free field extrapolations, are constructed to study a vertical range from the photosphere up to the low corona with a 45 km step size. The WGM method is applied as a function of height to all 13 flaring AR cases that are subject to certain selection criteria. We found that applying the WGM method between 1000 and 1800 km above the solar surface would improve the prediction of the flare onset time by around 2-8 hr. Certain caveats and an outlook for future work along these lines are also discussed. Title: Evolution of supersonic downflows in a sunspot Authors: Nelson, C. J.; Krishna Prasad, S.; Mathioudakis, M. Bibcode: 2020A&A...636A..35N Altcode: 2020arXiv200302489N Context. Supersonic downflows have been observed in transition region spectra above numerous sunspots, however, little research has been conducted to date into how persistent these signatures are within sunspots on timescales longer than a few hours.
Aims: We aim to analyse the lead sunspot of AR 12526 to infer the properties and evolution of supersonic downflows occurring within it using high-spatial and spectral resolution data.
Methods: We analysed 16 large, dense raster scans sampled by the Interface Region Imaging Spectrograph. These rasters tracked the lead sunspot of AR 12526 across the solar disc at discrete times between 27 March 2016 and 2 April 2016, providing spectral profiles from the Si IV, O IV, Mg II, and C II lines. Additionally, we studied one sit-and-stare observation acquired on 1 April 2016 centred on the sunspot to analyse the evolution of supersonic downflows on shorter timescales.
Results: Supersonic downflows are variable within this sunspot both in terms of spatial structuring and velocities. Thirteen of the 16 raster scans display some evidence of supersonic downflows in the Si IV 1394 Å line co-spatial to a sustained bright structure detected in the 1400 Å slit-jaw imaging channel; a peak velocity of 112 km s-1 is recorded on 29 March 2016. Evidence for supersonic downflows in the O IV 1401 Å line is found in 14 of these rasters; the spatial structuring in this line often differs from that inferred from the Si IV 1394 Å line. Only one example of a supersonic downflow is detected in the C II 1335 Å line and no downflows are found in the Mg II 2796 Å lines at these locations. In the sit-and-stare observations, no dual flow is initially detected, however, a supersonic downflow develops after approximately 60 min. This downflow accelerates from 73 km s-1 to close to 80 km s-1 in both the Si IV 1394 Å and O IV 1401 Å lines over the course of 20 min before the end of the observation.
Conclusions: Supersonic downflows are found in the Si IV 1394 Å line in 13 of the 16 rasters studied in this work. The morphology of these downflows evolved over the course of both hours and days and was often different in the Si IV 1394 Å and O IV 1401 Å lines. These events were found co-spatial to a bright region in the core of the Si IV 1394 Å line, which appeared to form at the footpoints of coronal fan loops. Our results indicate that one raster is not enough to conclusively draw inferences about the properties of supersonic downflows within a sunspot during its lifetime. Title: Multipoint Observations of Solar Wind Conditions and Magnetopause Motion Authors: Bagheri, F.; Lopez, R. E.; Dredger, P. M.; Bonde, R. E. F.; Bui, M.; Chapagain, N.; Nelson, C.; Xing, C. Bibcode: 2019AGUFMSM51C3198B Altcode: We study the magnetopause motion and structure based on observation from multiple crossings of the magnetopause of THEMIS A, D and E with simultaneous solar wind observations from Wind, ACE, THEMIS B, and THEMIS C. The solar wind data shows the IMF was radial and the velocity of solar wind was almost constant. The THEMIS A, D and E observations are consistent with the classic picture of pressure balance across the magnetopause. The thickness of the Chapman-Ferraro current layer is about one gyro diameter. The average magnetopause speeds were in the low 10's of km/s, however, speeds up to 100km/s were observed. During this period there is no evidence of hot flow anomalies in the magnetosheath near the magnetopause. Although the orientation of the IMF during the observations would have been predicted to cause wavy motions of the magnetopause boundary, in our study there is no evidence of such kind of motion. Title: Co-spatial velocity and magnetic swirls in the simulated solar photosphere Authors: Liu, Jiajia; Carlsson, Mats; Nelson, Chris J.; Erdélyi, Robert Bibcode: 2019A&A...632A..97L Altcode: 2019arXiv191110923L Context. Velocity or intensity swirls have now been shown to be widely present throughout the photosphere and chromosphere. It has been suggested that these events could contribute to the heating of the upper solar atmosphere, via exciting Alfvén pulses, which could carry significant amounts of energy. However, the conjectured necessary physical conditions for their excitation, that the magnetic field rotates co-spatially and co-temporally with the velocity field, has not been verified.
Aims: We aim to understand whether photospheric velocity swirls exist co-spatially and co-temporally with photospheric magnetic swirls, in order to demonstrate the link between swirls and pulses.
Methods: The automated swirl detection algorithm (ASDA) is applied to the photospheric horizontal velocity and vertical magnetic fields obtained from a series of realistic numerical simulations using the radiative magnetohydrodynamics (RMHD) code Bifrost. The spatial relationship between the detected velocity and magnetic swirls is further investigated via a well-defined correlation index (CI) study.
Results: On average, there are ∼63 short-lived photospheric velocity swirls (with lifetimes mostly less than 20 s, and average radius of ∼37 km and rotating speeds of ∼2.5 km s-1) detected in a field of view (FOV) of 6 × 6 Mm-2, implying a total population of velocity swirls of ∼1.06 × 107 in the solar photosphere. More than 80% of the detected velocity swirls are found to be accompanied by local magnetic concentrations in intergranular lanes. On average, ∼71% of the detected velocity swirls have been found to co-exist with photospheric magnetic swirls with the same rotating direction.
Conclusions: The co-temporal and co-spatial rotation in the photospheric velocity and magnetic fields provide evidence that the conjectured condition for the excitation of Alfvén pulses by photospheric swirls is fulfilled. Title: Investigation of light ion fusion reactions with plasma discharges Authors: Schenkel, T.; Persaud, A.; Wang, H.; Seidl, P. A.; MacFadyen, R.; Nelson, C.; Waldron, W. L.; Vay, J. -L.; Deblonde, G.; Wen, B.; Chiang, Y. -M.; MacLeod, B. P.; Ji, Q. Bibcode: 2019JAP...126t3302S Altcode: 2019arXiv190503400S The scaling of reaction yields in light ion fusion to low reaction energies is important for our understanding of stellar fuel chains and the development of future energy technologies. Experiments become progressively more challenging at lower reaction energies due to the exponential drop of fusion cross sections below the Coulomb barrier. We report on experiments where deuterium-deuterium (D-D) fusion reactions are studied in a pulsed plasma in the glow discharge regime using a benchtop apparatus. We model plasma conditions using particle-in-cell codes. Advantages of this approach are relatively high peak ion currents and current densities (0.1 to several A/cm2) that can be applied to metal wire cathodes for several days. We detect neutrons from D-D reactions with scintillator-based detectors. For palladium targets, we find neutron yields as a function of cathode voltage that are over 100 times higher than yields expected for bare nuclei fusion at ion energies below 2 keV (center of mass frame). A possible explanation is a correction to the ion energy due to an electron screening potential of 1000 ± 250 eV, which increases the probability for tunneling through the repulsive Coulomb barrier. Our compact, robust setup enables parametric studies of this effect at relatively low reaction energies. Title: Spatially Resolved Signatures of Bidirectional Flows Observed in Inverted-Y Shaped Jets Authors: Nelson, C. J.; Freij, N.; Bennett, S.; Erdélyi, R.; Mathioudakis, M. Bibcode: 2019ApJ...883..115N Altcode: 2019arXiv190805132N Numerous apparent signatures of magnetic reconnection have been reported in the solar photosphere, including inverted-Y shaped jets. The reconnection at these sites is expected to cause localized bidirectional flows and extended shock waves; however, these signatures are rarely observed as extremely high spatial-resolution data are required. Here, we use Hα imaging data sampled by the Swedish Solar Telescope’s CRisp Imaging SpectroPolarimeter to investigate whether bidirectional flows can be detected within inverted-Y shaped jets near the solar limb. These jets are apparent in the Hα line wings, while no signature of either jet is observed in the Hα line core, implying reconnection took place below the chromospheric canopy. Asymmetries in the Hα line profiles along the legs of the jets indicate the presence of bidirectional flows, consistent with cartoon models of reconnection in chromospheric anemone jets. These asymmetries are present for over two minutes, longer than the lifetimes of Rapid Blue Excursions, and beyond ±1 Å into the wings of the line indicating that flows within the inverted-Y shaped jets are responsible for the imbalance in the profiles, rather than motions in the foreground. Additionally, surges form following the occurrence of the inverted-Y shaped jets. This surge formation is consistent with models, which suggests such events could be caused by the propagation of shock waves from reconnection sites in the photosphere to the upper atmosphere. Overall, our results provide evidence that magnetic reconnection in the photosphere can cause bidirectional flows within inverted-Y shaped jets and could be the driver of surges. Title: Evidence of ubiquitous Alfvén pulses transporting energy from the photosphere to the upper chromosphere Authors: Liu, Jiajia; Nelson, Chris J.; Snow, Ben; Wang, Yuming; Erdélyi, Robert Bibcode: 2019NatCo..10.3504L Altcode: The multi-million degree temperature increase from the middle to the upper solar atmosphere is one of the most fascinating puzzles in plasma-astrophysics. Although magnetic waves might transport enough energy from the photosphere to heat up the local chromosphere and corona, observationally validating their ubiquity has proved challenging. Here, we show observational evidence that ubiquitous Alfvén pulses are excited by prevalent intensity swirls in the solar photosphere. Correlation analysis between swirls detected at different heights in the solar atmosphere, together with realistic numerical simulations, show that these Alfvén pulses propagate upwards and reach chromospheric layers. We found that Alfvén pulses carry sufficient energy flux (1.9 to 7.7 kW m-2) to balance the local upper chromospheric energy losses ( 0.1 kW m-2) in quiet regions. Whether this wave energy flux is actually dissipated in the chromosphere and can lead to heating that balances the losses is still an open question. Title: The Effect Of Cooling On Driven Kink Oscillations Of Coronal Loops Authors: Nelson, Chris J.; Shukhobodskiy, Alexander A.; Erdélyi, Robertus; Mathioudakis, Mihalis Bibcode: 2019FrASS...6...45N Altcode: 2019arXiv190513137N Ever since their detection two decades ago, standing kink oscillations in coronal loops have been extensively studied both observationally and theoretically. Almost all driven coronal loop oscillations (e.g., by flares) are observed to damp through time often with Gaussian or exponential profiles. Intriguingly, however, it has been shown theoretically that the amplitudes of some oscillations could be modified from Gaussian or exponential profiles if cooling is present in the coronal loop systems. Indeed, in some cases the oscillation amplitude can even increase through time. In this article, we analyse a flare-driven coronal loop oscillation observed by the Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA) in order to investigate whether models of cooling can explain the amplitude profile of the oscillation and whether hints of cooling can be found in the intensity evolution of several SDO/AIA filters. During the oscillation of this loop system, the kink mode amplitude appears to differ from a typical Gaussian or exponential profile with some hints being present that the amplitude increases. The application of cooling coronal loop modelling allowed us to estimate the density ratio between the loop and the background plasma, with a ratio of between 2.05-2.35 being returned. Overall, our results indicate that consideration of the thermal evolution of coronal loop systems can allow us to better describe oscillations in these structures and return more accurate estimates of the physical properties of the loops (e.g., density, scale height, magnetic field strength). Title: Automated Swirl Detection Algorithm (ASDA) and Its Application to Simulation and Observational Data Authors: Liu, Jiajia; Nelson, Chris J.; Erdélyi, Robertus Bibcode: 2019ApJ...872...22L Altcode: 2018arXiv180402931L Swirling motions in the solar atmosphere have been widely observed in recent years and suggested to play a key role in channeling energy from the photosphere into the corona. Here, we present a newly developed Automated Swirl Detection Algorithm (ASDA) and discuss its applications. ASDA is found to be very proficient at detecting swirls in a variety of synthetic data with various levels of noise, implying our subsequent scientific results are astute. Applying ASDA to photospheric observations with a pixel size of 39.2 km sampled by the Solar Optical Telescope on board Hinode suggests a total number of 1.62 × 105 swirls in the photosphere, with an average radius and rotating speed of ∼290 km and <1.0 km s-1, respectively. Comparisons between swirls detected in Bifrost numerical MHD simulations and both ground-based and space-borne observations suggest that (1) the spatial resolution of data plays a vital role in the total number and radii of swirls detected, and (2) noise introduced by seeing effects could decrease the detection rate of swirls, but has no significant influences in determining their inferred properties. All results have shown that there is no significant difference in the analyzed properties between counterclockwise or clockwise rotating swirls. About 70% of swirls are located in intergranular lanes. Most of the swirls have lifetimes of less than twice the cadences, meaning future research should aim to use data with much higher cadences than 6 s. In the conclusions, we propose some promising future research applications where ASDA may provide useful insight. Title: Solar Ultraviolet Bursts Authors: Young, Peter R.; Tian, Hui; Peter, Hardi; Rutten, Robert J.; Nelson, Chris J.; Huang, Zhenghua; Schmieder, Brigitte; Vissers, Gregal J. M.; Toriumi, Shin; Rouppe van der Voort, Luc H. M.; Madjarska, Maria S.; Danilovic, Sanja; Berlicki, Arkadiusz; Chitta, L. P.; Cheung, Mark C. M.; Madsen, Chad; Reardon, Kevin P.; Katsukawa, Yukio; Heinzel, Petr Bibcode: 2018SSRv..214..120Y Altcode: 2018arXiv180505850Y The term "ultraviolet (UV) burst" is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling opposite-polarity fields in the photosphere that occur in emerging flux regions, moving magnetic features in sunspot moats, and sunspot light bridges. We also compare UV bursts with similar transition-region phenomena found previously in solar ultraviolet spectrometry and with similar phenomena at optical wavelengths, in particular Ellerman bombs. Akin to the latter, UV bursts are probably small-scale magnetic reconnection events occurring in the low atmosphere, at photospheric and/or chromospheric heights. Their intense emission in lines with optically thin formation gives unique diagnostic opportunities for studying the physics of magnetic reconnection in the low solar atmosphere. This paper is a review report from an International Space Science Institute team that met in 2016-2017. Title: Magnetic Braids in Eruptions of a Spiral Structure in the Solar Atmosphere Authors: Huang, Zhenghua; Xia, Lidong; Nelson, Chris J.; Liu, Jiajia; Wiegelmann, Thomas; Tian, Hui; Klimchuk, James A.; Chen, Yao; Li, Bo Bibcode: 2018ApJ...854...80H Altcode: 2018arXiv180105967H We report on high-resolution imaging and spectral observations of eruptions of a spiral structure in the transition region, which were taken with the Interface Region Imaging Spectrograph, and the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The eruption coincided with the appearance of two series of jets, with velocities comparable to the Alfvén speeds in their footpoints. Several pieces of evidence of magnetic braiding in the eruption are revealed, including localized bright knots, multiple well-separated jet threads, transition region explosive events, and the fact that all three of these are falling into the same locations within the eruptive structures. Through analysis of the extrapolated 3D magnetic field in the region, we found that the eruptive spiral structure corresponded well to locations of twisted magnetic flux tubes with varying curl values along their lengths. The eruption occurred where strong parallel currents, high squashing factors, and large twist numbers were obtained. The electron number density of the eruptive structure is found to be ∼3 × 1012 cm-3, indicating that a significant amount of mass could be pumped into the corona by the jets. Following the eruption, the extrapolations revealed a set of seemingly relaxed loops, which were visible in the AIA 94 Å channel, indicating temperatures of around 6.3 MK. With these observations, we suggest that magnetic braiding could be part of the mechanisms explaining the formation of solar eruption and the mass and energy supplement to the corona. Title: The formation of small-scale umbral brightenings in sunspot atmospheres Authors: Nelson, C. J.; Henriques, V. M. J.; Mathioudakis, M.; Keenan, F. P. Bibcode: 2017A&A...605A..14N Altcode: 2017arXiv170505617N Context. Sunspot atmospheres have been shown to be highly inhomogeneous hosting both quasi-stable and transient features, such as small-scale umbral brightenings (previously named "umbral micro-jets") and dark fibril-like events.
Aims: We seek to understand the morphological properties and formation mechanisms of small-scale umbral brightenings (analogous to umbral micro-jets). In addition, we aim to understand whether links between these events and short dynamic fibrils, umbral flashes, and umbral dots can be established.
Methods: A Swedish 1 m Solar Telescope (SST) filtergram time-series sampling the Ca II H line and a CRisp Imaging Spectro-Polarimeter (SST/CRISP) full-Stokes 15-point Ca II 8542 Å line scan dataset were used. The spatial resolutions of these datasets are close to 0.1'' and 0.18'' with cadences of 1.4 s and 29 s, respectively. These data allowed us to construct light-curves, plot line profiles, and to perform a weak-field approximation in order to infer the magnetic field strength.
Results: The average lifetime and lengths of the 54 small-scale brightenings identified in the sunspot umbra are found to be 44.2 s (σ = 20 s) and 0.56'' (σ = 0.14''), respectively. The spatial positioning and morphological evolution of these events in Ca II H filtergrams was investigated finding no evidence of parabolic or ballistic profiles nor a preference for co-spatial formation with umbral flashes. Line scans in Ca II 8542 Å and the presence of Stokes V profile reversals provided evidence that these events could form in a similar manner to umbral flashes in the chromosphere (I.e. through the formation of shocks either due to the steepening of localised wavefronts or due to the impact of returning material from short dynamic fibrils, a scenario we find evidence for). The application of the weak-field approximation indicated that changes in the line-of-sight magnetic field were not responsible for the modifications to the line profile and suggested that thermodynamic effects are, in fact, the actual cause of the increased emission. Finally, a sub-set of small-scale brightenings were observed to form at the foot-points of short dynamic fibrils.
Conclusions: The small-scale umbral brightenings studied here do not appear to be jet-like in nature. Instead they appear to be evidence of shock formation in the lower solar atmosphere. We found no correlation between the spatial locations where these events were observed and the occurrence of umbral dots and umbral flashes. These events have lifetimes and spectral signatures comparable to umbral flashes and are located at the footpoints of short dynamic fibrils, during or at the end of the red-shifted stage. It is possible that these features form due to the shocking of fibrilar material in the lower atmosphere upon its return under gravity. Title: IRIS Burst Spectra Co-spatial to a Quiet-Sun Ellerman-like Brightening Authors: Nelson, C. J.; Freij, N.; Reid, A.; Oliver, R.; Mathioudakis, M.; Erdélyi, R. Bibcode: 2017ApJ...845...16N Altcode: 2017arXiv170705080N Ellerman bombs (EBs) have been widely studied over the past two decades; however, only recently have the counterparts of these events been observed in the quiet-Sun. The aim of this article is to further understand small-scale quiet-Sun Ellerman-like brightenings (QSEBs) through research into their spectral signatures, including investigating whether the hot signatures associated with some EBs are also visible co-spatial to any QSEBs. We combine Hα and Ca II 8542 Å line scans at the solar limb with spectral and imaging data sampled by the Interface Region Imaging Spectrograph (IRIS). Twenty-one QSEBs were identified with average lifetimes, lengths, and widths measured to be around 120 s, 0.″63, and 0.″35, respectively. Three of these QSEBs displayed clear repetitive flaring through their lifetimes, comparable to the behavior of EBs in active regions. Two QSEBs in this sample occurred co-spatial to increased emission in SDO/AIA 1600 Å and IRIS slit-jaw imager 1400 Å data; however, these intensity increases were smaller than those reported co-spatially with EBs. One QSEB was also sampled by the IRIS slit during its lifetime, displaying increases in intensity in the Si IV 1393 Å and Si IV 1403 Å cores, as well as the C II and Mg II line wings, analogous to IRIS bursts (IBs). Using RADYN simulations, we are unable to reproduce the observed QSEB Hα and Ca II 8542 Å line profiles, leaving the question of the temperature stratification of QSEBs open. Our results imply that some QSEBs could be heated to transition region temperatures, suggesting that IB profiles should be observed throughout the quiet-Sun. Title: On the relationship between magnetic cancellation and UV burst formation Authors: Nelson, C. J.; Doyle, J. G.; Erdélyi, R. Bibcode: 2016MNRAS.463.2190N Altcode: 2016arXiv160806505N; 2016MNRAS.tmp.1156N Burst-like events with signatures in the UV are often observed co-spatial to strong line-of-sight photospheric magnetic fields. Several authors, for example, have noted the spatial relationship between Ellerman bombs (EBs) and moving magnetic features (MMFs), regions of flux which disconnect from a sunspot or pore before propagating away in the moat flow and often displaying evidence of cancellation. In this article, data collected by the Solar Dynamics Observatory's Helioseismic and Magnetic Imager and Atmospheric Imaging Assembly are analysed in an attempt to understand the potential links between such cancellation and UV burst formation. Two MMFs from AR 11579, three bi-poles from AR 11765, and six bi-poles (four of which were co-spatial to Interface Region Imaging Spectrograph bursts) in AR 11850 were identified for analysis. All of these cancellation features were found to have lifetimes of the order hours and cancellation rates of the order 1014-1015 Mx s-1. Hα line wing data from the Dunn Solar Telescope's Interferometric BIdimensional Spectrometer were also available for AR 11579 facilitating a discussion of links between MMFs and EBs. Using an algebraic model of photospheric magnetic reconnection, the measured cancellation rates are then used to ascertain estimates of certain quantities (such as upflow speeds, jet extents, and potential energy releases), which compared reasonably to the properties of EBs reported within the literature. Our results suggest that cancellation rates of the order measured here are capable of supplying enough energy to drive certain UV bursts (including EBs), however, they are not a guaranteeing condition for burst formation. Title: Magnetic Flux Cancellation in Ellerman Bombs Authors: Reid, A.; Mathioudakis, M.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Henriques, V.; Ray, T. Bibcode: 2016ApJ...823..110R Altcode: 2016arXiv160307100R Ellerman Bombs (EBs) are often found to be co-spatial with bipolar photospheric magnetic fields. We use Hα imaging spectroscopy along with Fe I 6302.5 Å spectropolarimetry from the Swedish 1 m Solar Telescope (SST), combined with data from the Solar Dynamic Observatory, to study EBs and the evolution of the local magnetic fields at EB locations. EBs are found via an EB detection and tracking algorithm. Using NICOLE inversions of the spectropolarimetric data, we find that, on average, (3.43 ± 0.49) × 1024 erg of stored magnetic energy disappears from the bipolar region during EB burning. The inversions also show flux cancellation rates of 1014-1015 Mx s-1 and temperature enhancements of 200 K at the detection footpoints. We investigate the near-simultaneous flaring of EBs due to co-temporal flux emergence from a sunspot, which shows a decrease in transverse velocity when interacting with an existing, stationary area of opposite polarity magnetic flux, resulting in the formation of the EBs. We also show that these EBs can be fueled further by additional, faster moving, negative magnetic flux regions. Title: High-cadence observations of spicular-type events on the Sun Authors: Shetye, J.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Kuridze, D.; Henriques, V.; Woeger, F.; Ray, T. Bibcode: 2016A&A...589A...3S Altcode: 2016arXiv160108087S Context. Chromospheric observations taken at high-cadence and high-spatial resolution show a range of spicule-like features, including Type-I, Type-II (as well as rapid blue-shifted excursions (RBEs) and rapid red-shifted excursions (RREs) which are thought to be on-disk counterparts of Type-II spicules) and those which seem to appear within a few seconds, which if interpreted as flows would imply mass flow velocities in excess of 1000 km s-1.
Aims: This article seeks to quantify and study rapidly appearing spicular-type events. We also compare the multi-object multi-frame blind deconvolution (MOMFBD) and speckle reconstruction techniques to understand if these spicules are more favourably observed using a particular technique.
Methods: We use spectral imaging observations taken with the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1-m Solar Telescope. Data was sampled at multiple positions within the Hα line profile for both an on-disk and limb location.
Results: The data is host to numerous rapidly appearing features which are observed at different locations within the Hα line profile. The feature's durations vary between 10-20 s and lengths around 3500 km. Sometimes, a time delay in their appearance between the blue and red wings of 3-5 s is evident, whereas, sometimes they are near simultaneous. In some instances, features are observed to fade and then re-emerge at the same location several tens of seconds later.
Conclusions: We provide the first statistical analysis of these spicules and suggest that these observations can be interpreted as the line-of-sight (LOS) movement of highly dynamic spicules moving in and out of the narrow 60 mÅ transmission filter that is used to observe in different parts of the Hα line profile. The LOS velocity component of the observed fast chromospheric features, manifested as Doppler shifts, are responsible for their appearance in the red and blue wings of Hα line. Additional work involving data at other wavelengths is required to investigate the nature of their possible wave-like activity. Title: High Cadence Observations and Analysis of Spicular-type Events Using CRISP Onboard SST Authors: Shetye, J.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Kuridze, D. Bibcode: 2016ASPC..504..115S Altcode: We present spectroscopic and imaging observations of apparent ultra-fast spicule-like features observed with CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m Solar Telescope (SST). The data shows spicules with an apparent velocity above 500 km s-1, very short lifetimes of up to 20 s and length/height around 3500 km. The spicules are seen as dark absorption structures in the Hα wings ±516 mÅ, ±774 mÅ and ±1032 mÅ which suddenly appear and disappear from the FOV. These features show a time delay in their appearance in the blue and red wings by 3-5 s. We suggest that their appearance/disappearance is due to their Doppler motion in and out of the 60 mÅ filter. See Fig. 1 for the evolution of the event at two line positions. Title: On The Role of MHD Waves in Heating Localised Magnetic Structures Authors: Erdélyi, R.; Nelson, C. J. Bibcode: 2016ASPC..504..153E Altcode: Satellite and ground-based observations from e.g. SOHO, TRACE, STEREO, Hinode, SDO and IRIS to DST/ROSA, IBIS, CoMP, STT/CRISP have provided a wealth of evidence of waves and oscillations present in a wide range of spatial scales of the magnetised solar atmosphere. Our understanding about localised solar structures has been considerably changed in light of these high spatial and time resolution observations. However, MHD waves not only enable us to perform sub-resolution magneto-seismology of magnetic waveguides but are also potential candidates to carry and damp the necessary non-thermal energy in these localised waveguides. First, we will briefly outline the basic recent developments in MHD wave theory focussing on linear waves. Next, we discuss the role of the most frequently studied wave classes, including the Alfven, and magneto-acoustic kink and sausage waves. The current theoretical (and often difficult) interpretations of the detected solar atmospheric wave and oscillatory phenomena within the framework of MHD will be shown. Last, the latest reported observational findings of potential MHD wave flux, in terms of localised plasma heating, in the solar atmosphere is discussed, bringing us closer to solve the coronal heating problem. Title: Small-scale Structuring of Ellerman Bombs at the Solar Limb Authors: Nelson, C. J.; Scullion, E. M.; Doyle, J. G.; Freij, N.; Erdélyi, R. Bibcode: 2015ApJ...798...19N Altcode: 2014arXiv1410.5715N Ellerman bombs (EBs) have been widely studied in recent years due to their dynamic, explosive nature and apparent links to the underlying photospheric magnetic field implying that they may be formed by magnetic reconnection in the photosphere. Despite a plethora of researches discussing the morphologies of EBs, there has been a limited investigation of how these events appear at the limb, specifically, whether they manifest as vertical extensions away from the disk. In this article, we make use of high-resolution, high-cadence observations of an Active Region at the solar limb, collected by the CRisp Imaging SpectroPolarimeter (CRISP) instrument, to identify EBs and infer their physical properties. The upper atmosphere is also probed using the Solar Dynamic Observatory's Atmospheric Imaging Assembly (SDO/AIA). We analyze 22 EB events evident within these data, finding that 20 appear to follow a parabolic path away from the solar surface at an average speed of 9 km s-1, extending away from their source by 580 km, before retreating back at a similar speed. These results show strong evidence of vertical motions associated with EBs, possibly explaining the dynamical "flaring" (changing in area and intensity) observed in on-disk events. Two in-depth case studies are also presented that highlight the unique dynamical nature of EBs within the lower solar atmosphere. The viewing angle of these observations allows for a direct linkage between these EBs and other small-scale events in the Hα line wings, including a potential flux emergence scenario. The findings presented here suggest that EBs could have a wider-reaching influence on the solar atmosphere than previously thought, as we reveal a direct linkage between EBs and an emerging small-scale loop, and other near-by small-scale explosive events. However, as previous research found, these extensions do not appear to impact upon the Hα line core, and are not observed by the SDO/AIA EUV filters. Title: The Detection of Upwardly Propagating Waves Channeling Energy from the Chromosphere to the Low Corona Authors: Freij, N.; Scullion, E. M.; Nelson, C. J.; Mumford, S.; Wedemeyer, S.; Erdélyi, R. Bibcode: 2014ApJ...791...61F Altcode: 2014arXiv1408.4621F There have been ubiquitous observations of wave-like motions in the solar atmosphere for decades. Recent improvements to space- and ground-based observatories have allowed the focus to shift to smaller magnetic structures on the solar surface. In this paper, high-resolution ground-based data taken using the Swedish 1 m Solar Telescope is combined with co-spatial and co-temporal data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) satellite to analyze running penumbral waves (RPWs). RPWs have always been thought to be radial wave propagation that occurs within sunspots. Recent research has suggested that they are in fact upwardly propagating field-aligned waves (UPWs). Here, RPWs within a solar pore are observed for the first time and are interpreted as UPWs due to the lack of a penumbra that is required to support RPWs. These UPWs are also observed co-spatially and co-temporally within several SDO/AIA elemental lines that sample the transition region and low corona. The observed UPWs are traveling at a horizontal velocity of around 17 ± 0.5 km s-1 and a minimum vertical velocity of 42 ± 21 km s-1. The estimated energy of the waves is around 150 W m-2, which is on the lower bound required to heat the quiet-Sun corona. This is a new, yet unconsidered source of wave energy within the solar chromosphere and low corona. Title: Effects of Stratification and Flows on P 1/ P 2 Ratios and Anti-node Shifts Within Closed Loop Structures Authors: Erdélyi, R.; Hague, A.; Nelson, C. J. Bibcode: 2014SoPh..289..167E Altcode: 2013arXiv1306.1051E The solar atmosphere is a dynamic environment, constantly evolving to form a wide range of magnetically dominated structures (coronal loops, spicules, prominences, etc.) which cover a significant percentage of the surface at any one time. Oscillations and waves in many of these structures are now widely observed and have led to the new analytic technique of solar magneto-seismology, where inferences of the background conditions of the plasma can be deduced by studying magneto-hydrodynamic (MHD) waves. Here, we generalise a novel magneto-seismological method designed to infer the density distribution of a bounded plasma structure from the relationship of its fundamental and subsequent harmonics. Observations of the solar atmosphere have emphatically shown that stratification, leading to complex density profiles within plasma structures, is common thereby rendering this work instantly accessible to solar physics. We show, in a dynamic waveguide, how the period ratio differs from the idealised harmonic ratios prevalent in homogeneous structures. These ratios show strong agreement with recent observational work. Next, anti-node shifts are also analysed. Using typical scaling parameters for bulk flows within atmospheric waveguides, e.g., coronal loops, it is found that significant anti-node shifts can be predicted, even to the order of 10 Mm. It would be highly encouraged to design specific observations to confirm the predicted anti-node shifts and apply the developed theory of solar magneto-seismology to gain more accurate waveguide diagnostics of the solar atmosphere. Title: Excitation of an outflow from the lower solar atmosphere and a co-temporal EUV transient brightening Authors: Nelson, C. J.; Doyle, J. G. Bibcode: 2013A&A...560A..31N Altcode: 2013arXiv1310.8490N
Aims: We analyse an absorption event within the Hα line wings, which has been identified as a surge, and the co-spatial evolution of an EUV brightening, with spatial and temporal scales analogous to a small blinker.
Methods: We conduct a multi-wavelength, multi-instrument analysis using high-cadence, high-resolution data, collected by the Interferometric BIdimensional Spectrometer on the Dunn Solar Telescope, as well as the space-borne Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager instruments on board the Solar Dynamics Observatory.
Results: One large absorption event situated within the plage region trailing the lead sunspot of AR 11579 is identified within the Hα line wings. This event is found to be co-spatially linked to a medium-scale (around 4'' in diameter) brightening within the transition region and corona. This ejection appears to have a parabolic evolution, first forming in the Hα blue wing before fading and reappearing in the Hα red wing, and comprises a number of smaller fibril events. The line-of-sight photospheric magnetic field shows no evidence of cancellation leading to this event.
Conclusions: Our research has identified clear evidence that at least a subset of transient brightening events in the transition region is linked to the influx of cooler plasma from the lower solar atmosphere during large eruptive events, such as surges. These observations agree with previous numerical researches on the nature of blinkers and, therefore, suggest that magnetic reconnection is the driver of the analysed surge events; however, further research is required to confirm this.

A movie attached to Fig. 2 is available in electronic form at http://www.aanda.org Title: Ellerman Bombs—Evidence for Magnetic Reconnection in the Lower Solar Atmosphere Authors: Nelson, C. J.; Shelyag, S.; Mathioudakis, M.; Doyle, J. G.; Madjarska, M. S.; Uitenbroek, H.; Erdélyi, R. Bibcode: 2013ApJ...779..125N Altcode: 2013arXiv1310.7756N The presence of photospheric magnetic reconnection has long been thought to give rise to short and impulsive events, such as Ellerman bombs (EBs) and Type II spicules. In this article, we combine high-resolution, high-cadence observations from the Interferometric BIdimensional Spectrometer and Rapid Oscillations in the Solar Atmosphere instruments at the Dunn Solar Telescope, National Solar Observatory, New Mexico, with co-aligned Solar Dynamics Observatory Atmospheric Imaging Assembly and Hinode Solar Optical Telescope (SOT) data to observe small-scale events situated within an active region. These data are then compared with state-of-the-art numerical simulations of the lower atmosphere made using the MURaM code. It is found that brightenings, in both the observations and the simulations, of the wings of the Hα line profile, interpreted as EBs, are often spatially correlated with increases in the intensity of the Fe I λ6302.5 line core. Bipolar regions inferred from Hinode/SOT magnetic field data show evidence of flux cancellation associated, co-spatially, with these EBs, suggesting that magnetic reconnection could be a driver of these high-energy events. Through the analysis of similar events in the simulated lower atmosphere, we are able to infer that line profiles analogous to the observations occur co-spatially with regions of strong opposite-polarity magnetic flux. These observed events and their simulated counterparts are interpreted as evidence of photospheric magnetic reconnection at scales observable using current observational instrumentation. Title: Statistical Analysis of Small Ellerman Bomb Events Authors: Nelson, C. J.; Doyle, J. G.; Erdélyi, R.; Huang, Z.; Madjarska, M. S.; Mathioudakis, M.; Mumford, S. J.; Reardon, K. Bibcode: 2013SoPh..283..307N Altcode: 2013arXiv1301.1351N The properties of Ellerman bombs (EBs), small-scale brightenings in the Hα line wings, have proved difficult to establish because their size is close to the spatial resolution of even the most advanced telescopes. Here, we aim to infer the size and lifetime of EBs using high-resolution data of an emerging active region collected using the Interferometric BIdimensional Spectrometer (IBIS) and Rapid Oscillations of the Solar Atmosphere (ROSA) instruments as well as the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We develop an algorithm to track EBs through their evolution, finding that EBs can often be much smaller (around 0.3″) and shorter-lived (less than one minute) than previous estimates. A correlation between G-band magnetic bright points and EBs is also found. Combining SDO/HMI and G-band data gives a good proxy of the polarity for the vertical magnetic field. It is found that EBs often occur both over regions of opposite polarity flux and strong unipolar fields, possibly hinting at magnetic reconnection as a driver of these events.The energetics of EB events is found to follow a power-law distribution in the range of a nanoflare (1022−25 ergs). Title: Ellerman bombs: small-scale brightenings in the photosphere Authors: Nelson, C. J.; Doyle, J. G.; Erdélyi, R.; Madjarska, M.; Mumford, S. J. Bibcode: 2013MmSAI..84..436N Altcode: Observations of small-scale events in the solar atmosphere are limited by the spatial and temporal resolutions of the current crop of observational instruments. Both high-cadence and high-resolution observations of the photosphere have shown the continued dynamics to extremely small-scales. Ellerman bombs, brightening events in the wings of the Halpha line profile, are one example of small-scale, short-lived events which have been widely studied due to their fast dynamics in recent years. By combining the Interferometric BIdimensional Spectrometer (IBIS) instrument with the Helioseismic and Magnetic Imager (HMI/SDO), we show the small-scale nature of these events, as well as their link to the background magnetic field. It is found that EBs can be much smaller and shorter-lived than previous estimates have stated, implying the continued dynamics of the solar atmosphere below current observational limits. Title: Microlensing Binaries with Candidate Brown Dwarf Companions Authors: Shin, I. -G.; Han, C.; Gould, A.; Udalski, A.; Sumi, T.; Dominik, M.; Beaulieu, J. -P.; Tsapras, Y.; Bozza, V.; Szymański, M. K.; Kubiak, M.; Soszyński, I.; Pietrzyński, G.; Poleski, R.; Ulaczyk, K.; Pietrukowicz, P.; Kozłowski, S.; Skowron, J.; Wyrzykowski, Ł.; OGLE Collaboration; Abe, F.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Furusawa, K.; Hayashi, F.; Hearnshaw, J. B.; Hosaka, S.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Kobara, S.; Korpela, A.; Lin, W.; Ling, C. H.; Makita, S.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Nagaya, M.; Nishimoto, K.; Ohnishi, K.; Okumura, T.; Omori, K.; Perrott, Y. C.; Rattenbury, N.; Saito, To.; Skuljan, L.; Sullivan, D. J.; Suzuki, D.; Sweatman, W. L.; Tristram, P. J.; Wada, K.; Yock, P. C. M.; MOA Collaboration; Christie, G. W.; Depoy, D. L.; Dong, S.; Gal-Yam, A.; Gaudi, B. S.; Hung, L. -W.; Janczak, J.; Kaspi, S.; Maoz, D.; McCormick, J.; McGregor, D.; Moorhouse, D.; Muñoz, J. A.; Natusch, T.; Nelson, C.; Pogge, R. W.; Tan, T. -G.; Polishook, D.; Shvartzvald, Y.; Shporer, A.; Thornley, G.; Malamud, U.; Yee, J. C.; Choi, J. -Y.; Jung, Y. -K.; Park, H.; Lee, C. -U.; Park, B. -G.; Koo, J. -R.; μFUN Collaboration; Bajek, D.; Bramich, D. M.; Browne, P.; Horne, K.; Ipatov, S.; Snodgrass, C.; Steele, I.; Street, R.; Alsubai, K. A.; Burgdorf, M. J.; Calchi Novati, S.; Dodds, P.; Dreizler, S.; Fang, X. -S.; Grundahl, F.; Gu, C. -H.; Hardis, S.; Harpsøe, K.; Hinse, T. C.; Hundertmark, M.; Jessen-Hansen, J.; Jørgensen, U. G.; Kains, N.; Kerins, E.; Liebig, C.; Lund, M.; Lundkvist, M.; Mancini, L.; Mathiasen, M.; Hornstrup, A.; Penny, M. T.; Proft, S.; Rahvar, S.; Ricci, D.; Scarpetta, G.; Skottfelt, J.; Southworth, J.; Surdej, J.; Tregloan-Reed, J.; Wertz, O.; Zimmer, F.; Albrow, M. D.; Batista, V.; Brillant, S.; Caldwell, J. A. R.; Calitz, J. J.; Cassan, A.; Cole, A.; Cook, K. H.; Corrales, E.; Coutures, Ch.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Greenhill, J.; Hill, K.; Hoffman, M.; Kane, S. R.; Kubas, D.; Marquette, J. -B.; Martin, R.; Meintjes, P.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Wambsganss, J.; Williams, A.; Vinter, C.; Zub, M. Bibcode: 2012ApJ...760..116S Altcode: 2012arXiv1208.2323S Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during the 2004-2011 observation seasons. Based on the low mass ratio criterion of q < 0.2, we found seven candidate events: OGLE-2004-BLG-035, OGLE-2004-BLG-039, OGLE-2007-BLG-006, OGLE-2007-BLG-399/MOA-2007-BLG-334, MOA-2011-BLG-104/OGLE-2011-BLG-0172, MOA-2011-BLG-149, and MOA-201-BLG-278/OGLE-2011-BLG-012N. Among them, we are able to confirm that the companions of the lenses of MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 are brown dwarfs by determining the mass of the lens based on the simultaneous measurement of the Einstein radius and the lens parallax. The measured masses of the brown dwarf companions are 0.02 ± 0.01 M and 0.019 ± 0.002 M for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149, respectively, and both companions are orbiting low-mass M dwarf host stars. More microlensing brown dwarfs are expected to be detected as the number of lensing events with well-covered light curves increases with new-generation searches. Title: Characterizing Lenses and Lensed Stars of High-magnification Single-lens Gravitational Microlensing Events with Lenses Passing over Source Stars Authors: Choi, J. -Y.; Shin, I. -G.; Park, S. -Y.; Han, C.; Gould, A.; Sumi, T.; Udalski, A.; Beaulieu, J. -P.; Street, R.; Dominik, M.; Allen, W.; Almeida, L. A.; Bos, M.; Christie, G. W.; Depoy, D. L.; Dong, S.; Drummond, J.; Gal-Yam, A.; Gaudi, B. S.; Henderson, C. B.; Hung, L. -W.; Jablonski, F.; Janczak, J.; Lee, C. -U.; Mallia, F.; Maury, A.; McCormick, J.; McGregor, D.; Monard, L. A. G.; Moorhouse, D.; Muñoz, J. A.; Natusch, T.; Nelson, C.; Park, B. -G.; Pogge, R. W.; "TG" Tan, T. -G.; Thornley, G.; Yee, J. C.; μFUN Collaboration; Abe, F.; Barnard, E.; Baudry, J.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Furusawa, K.; Hayashi, F.; Hearnshaw, J. B.; Hosaka, S.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Kobara, S.; Korpela, A.; Lin, W.; Ling, C. H.; Makita, S.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Nagaya, M.; Nishimoto, K.; Ohnishi, K.; Okumura, T.; Omori, K.; Perrott, Y. C.; Rattenbury, N.; Saito, To.; Skuljan, L.; Sullivan, D. J.; Suzuki, D.; Suzuki, K.; Sweatman, W. L.; Takino, S.; Tristram, P. J.; Wada, K.; Yock, P. C. M.; MOA Collaboration; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Poleski, R.; Ulaczyk, K.; Wyrzykowski, Ł.; Kozłowski, S.; Pietrukowicz, P.; OGLE Collaboration; Albrow, M. D.; Bachelet, E.; Batista, V.; Bennett, C. S.; Bowens-Rubin, R.; Brillant, S.; Cassan, A.; Cole, A.; Corrales, E.; Coutures, Ch.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Greenhill, J.; Kane, S. R.; Menzies, J.; Sahu, K. C.; Wambsganss, J.; Williams, A.; Zub, M.; PLANET Collaboration; Allan, A.; Bramich, D. M.; Browne, P.; Clay, N.; Fraser, S.; Horne, K.; Kains, N.; Mottram, C.; Snodgrass, C.; Steele, I.; Tsapras, Y.; RoboNet Collaboration; Alsubai, K. A.; Bozza, V.; Burgdorf, M. J.; Calchi Novati, S.; Dodds, P.; Dreizler, S.; Finet, F.; Gerner, T.; Glitrup, M.; Grundahl, F.; Hardis, S.; Harpsøe, K.; Hinse, T. C.; Hundertmark, M.; Jørgensen, U. G.; Kerins, E.; Liebig, C.; Maier, G.; Mancini, L.; Mathiasen, M.; Penny, M. T.; Proft, S.; Rahvar, S.; Ricci, D.; Scarpetta, G.; Schäfer, S.; Schönebeck, F.; Skottfelt, J.; Surdej, J.; Southworth, J.; Zimmer, F.; MiNDSTEp Consortium Bibcode: 2012ApJ...751...41C Altcode: 2011arXiv1111.4032C We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all of the events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For seven events, we measure the Einstein radii and the lens-source relative proper motions. Among them, five events are found to have Einstein radii of less than 0.2 mas, making the lenses very low mass star or brown dwarf candidates. For MOA-2011-BLG-274, especially, the small Einstein radius of θE ~ 0.08 mas combined with the short timescale of t E ~ 2.7 days suggests the possibility that the lens is a free-floating planet. For MOA-2009-BLG-174, we measure the lens parallax and thus uniquely determine the physical parameters of the lens. We also find that the measured lens mass of ~0.84 M is consistent with that of a star blended with the source, suggesting that the blend is likely to be the lens. Although we did not find planetary signals for any of the events, we provide exclusion diagrams showing the confidence levels excluding the existence of a planet as a function of the separation and mass ratio. Title: Microlensing Binaries Discovered through High-magnification Channel Authors: Shin, I. -G.; Choi, J. -Y.; Park, S. -Y.; Han, C.; Gould, A.; Sumi, T.; Udalski, A.; Beaulieu, J. -P.; Dominik, M.; Allen, W.; Bos, M.; Christie, G. W.; Depoy, D. L.; Dong, S.; Drummond, J.; Gal-Yam, A.; Gaudi, B. S.; Hung, L. -W.; Janczak, J.; Kaspi, S.; Lee, C. -U.; Mallia, F.; Maoz, D.; Maury, A.; McCormick, J.; Monard, L. A. G.; Moorhouse, D.; Muñoz, J. A.; Natusch, T.; Nelson, C.; Park, B. -G.; Pogge, R. W.; Polishook, D.; Shvartzvald, Y.; Shporer, A.; Thornley, G.; Yee, J. C.; μFUN Collaboration; Abe, F.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Fukui, A.; Furusawa, K.; Hayashi, F.; Hearnshaw, J. B.; Hosaka, S.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Kobara, S.; Korpela, A.; Lin, W.; Ling, C. H.; Makita, S.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Nagaya, M.; Nishimoto, K.; Ohnishi, K.; Okumura, T.; Omori, K.; Perrott, Y. C.; Rattenbury, N.; Saito, To.; Skuljan, L.; Sullivan, D. J.; Suzuki, D.; Sweatman, W. L.; Tristram, P. J.; Wada, K.; Yock, P. C. M.; MOA Collaboration; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Poleski, R.; Ulaczyk, K.; Wyrzykowski, Ł.; Kozłowski, S.; Pietrukowicz, P.; OGLE Collaboration; Albrow, M. D.; Batista, V.; Bramich, D. M.; Brillant, S.; Caldwell, J. A. R.; Calitz, J. J.; Cassan, A.; Cole, A.; Cook, K. H.; Corrales, E.; Coutures, Ch.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Greenhill, J.; Hoffman, M.; Jørgensen, U. G.; Kane, S. R.; Kubas, D.; Marquette, J. -B.; Martin, R.; Meintjes, P.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Wambsganss, J.; Williams, A.; Vinter, C.; Zub, M.; PLANET Collaboration; Allan, A.; Browne, P.; Horne, K.; Snodgrass, C.; Steele, I.; Street, R.; Tsapras, Y.; RoboNet Collaboration; Alsubai, K. A.; Bozza, V.; Browne, P.; Burgdorf, M. J.; Calchi Novati, S.; Dodds, P.; Dreizler, S.; Finet, F.; Gerner, T.; Glitrup, M.; Grundahl, F.; Hardis, S.; Harpsøe, K.; Hessman, F. V.; Hinse, T. C.; Hundertmark, M.; Kains, N.; Kerins, E.; Liebig, C.; Maier, G.; Mancini, L.; Mathiasen, M.; Penny, M. T.; Proft, S.; Rahvar, S.; Ricci, D.; Scarpetta, G.; Schäfer, S.; Schönebeck, F.; Skottfelt, J.; Surdej, J.; Southworth, J.; Zimmer, F.; MiNDSTEp Consortium Bibcode: 2012ApJ...746..127S Altcode: 2011arXiv1109.3295S Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of eight binary-lensing events detected through the channel of high-magnification events during the seasons from 2007 to 2010. The perturbations, which are confined near the peak of the light curves, can be easily distinguished from the central perturbations caused by planets. However, the degeneracy between close and wide binary solutions cannot be resolved with a 3σ confidence level for three events, implying that the degeneracy would be an important obstacle in studying binary distributions. The dependence of the degeneracy on the lensing parameters is consistent with a theoretical prediction that the degeneracy becomes severe as the binary separation and the mass ratio deviate from the values of resonant caustics. The measured mass ratio of the event OGLE-2008-BLG-510/MOA-2008-BLG-369 is q ~ 0.1, making the companion of the lens a strong brown dwarf candidate. Title: Minor Planet Observations [H21 Astronomical Research Observatory, Westfield] Authors: Holmes, R.; Vorobjov, T.; Foglia, S.; Buzzi, L.; Johnson, L.; Nelson, C.; Smith, A.; Friel, M.; Hernandez, J.; Fulmore, C.; Bowden, R.; Linder, T.; Haithcock, J.; Yan, Y.; Mobley, D.; Allen, S.; Bell, C.; Urbanski, J.; Devore, H.; Bradshaw, A.; Colby, C.; Price, C.; Battles, E.; Lucas, M. Bibcode: 2012MPC..77794...2H Altcode: No abstract at ADS Title: Minor Planet Observations [H21 Astronomical Research Observatory, Westfield] Authors: Holmes, R.; Linder, T.; Mobley, D.; Bowden, R.; Vorobjov, T.; Buzzi, L.; Foglia, S.; Devore, H.; Bell, C.; Urbanski, J.; Friel, M.; Hernandez, J.; Colby, C.; Price, C.; Spell, K.; Battles, E.; Johnson, L.; Nelson, C.; Allen, S.; Trayah, K.; Yan, Y.; Trotman, A.; Lucas, M.; Owens, H. Bibcode: 2011MPC..77396...2H Altcode: No abstract at ADS Title: Minor Planet Observations [H21 Astronomical Research Observatory, Westfield] Authors: Holmes, R.; Vorobjov, T.; Buzzi, L.; Foglia, S.; Bell, C.; Urbanski, J.; Tombelli, M.; Mobley, D.; Bowden, R.; Owens, T.; Friel, M.; Lucas, M.; Haithcock, J.; Battles, E.; Colby, C.; Bradshaw, A.; Smith, A.; Trotman, A.; Fulmore, C.; Linder, T.; Yan, Y.; Devore, H.; Vorobjov, M. T.; Johnson, L.; Hernandez, J.; Nelson, C.; Mugrage, M.; Price, C.; Allen, S.; Trayah, K.; Owens, H.; Spell, K. Bibcode: 2011MPC..77006...1H Altcode: No abstract at ADS Title: Minor Planet Observations [H21 Astronomical Research Observatory, Westfield] Authors: Holmes, R.; Linder, T.; Vorobjov, T.; Urbanski, J.; Foglia, S.; Buzzi, L.; Dankov, K.; Vorobjov, M. T.; Bone, J.; Faircloth, S.; Yan, Y.; Devore, H.; Bowden, R.; Fulmore, C.; Hernandez, J.; Friel, M.; Battles, E.; Lucas, M.; Owens, T.; Mobley, D.; Bradshaw, A.; Spell, K.; Smith, A.; Johnson, L.; Allen, S.; Colby, C.; Rozier, K.; Price, C.; Nelson, C.; Trayah, K. Bibcode: 2011MPC..76018...1H Altcode: No abstract at ADS Title: Vibration-Induced PM Noise in Oscillators and Measurements of Correlation with Vibration Sensors Authors: Howe, D. A.; Lanfranchi, J. L.; Cutsinger, L.; Hati, A.; Nelson, C. Bibcode: 2005ptti.conf..494H Altcode: No abstract at ADS Title: [OIII] Emission Line Profiles in PG Quasars Authors: Nelson, C.; Plasek, A.; Thompson, A.; Gelderman, R.; Monroe, T. Bibcode: 2004ASPC..311...83N Altcode: 2004apsd.conf...83N We have obtained high S/N, high resolution profiles of the [OIII] 5007 emission line for all PG quasars with z<0.5. Previous studies have shown that the kinematics of the narrow line region gas (NLR) in active galaxies are predominantly due to gravitational motion in the host bulge potential. Thus, using the well established correlation between bulge velocity dispersion, σ*, and nuclear black hole mass, M, we can use the widths of the [OIII] line profiles to estimate M for the entire sample. If the [OIII] kinematics are in fact virial, this technique could provide independent estimates for M from SDSS quasar spectra. Title: Search for Kaluza-Klein Graviton Emission in pp¯ Collisions at √(s)=1.8 TeV Using the Missing Energy Signature Authors: Acosta, D.; Affolder, T.; Akimoto, H.; Albrow, M. G.; Ambrose, D.; Amidei, D.; Anikeev, K.; Antos, J.; Apollinari, G.; Arisawa, T.; Artikov, A.; Asakawa, T.; Ashmanskas, W.; Azfar, F.; Azzi-Bacchetta, P.; Bacchetta, N.; Bachacou, H.; Badgett, W.; Bailey, S.; de Barbaro, P.; Barbaro-Galtieri, A.; Barnes, V. E.; Barnett, B. A.; Baroiant, S.; Barone, M.; Bauer, G.; Bedeschi, F.; Behari, S.; Belforte, S.; Bell, W. H.; Bellettini, G.; Bellinger, J.; Benjamin, D.; Bensinger, J.; Beretvas, A.; Berryhill, J.; Bhatti, A.; Binkley, M.; Bisello, D.; Bishai, M.; Blair, R. E.; Blocker, C.; Bloom, K.; Blumenfeld, B.; Blusk, S. R.; Bocci, A.; Bodek, A.; Bolla, G.; Bolshov, A.; Bonushkin, Y.; Bortoletto, D.; Boudreau, J.; Brandl, A.; Bromberg, C.; Brozovic, M.; Brubaker, E.; Bruner, N.; Budagov, J.; Budd, H. S.; Burkett, K.; Busetto, G.; Byrum, K. L.; Cabrera, S.; Calafiura, P.; Campbell, M.; Carithers, W.; Carlson, J.; Carlsmith, D.; Caskey, W.; Castro, A.; Cauz, D.; Cerri, A.; Cerrito, L.; Chan, A. W.; Chang, P. S.; Chang, P. T.; Chapman, J.; Chen, C.; Chen, Y. C.; Cheng, M. -T.; Chertok, M.; Chiarelli, G.; Chirikov-Zorin, I.; Chlachidze, G.; Chlebana, F.; Christofek, L.; Chu, M. L.; Chung, J. Y.; Chung, W. -H.; Chung, Y. S.; Ciobanu, C. I.; Clark, A. G.; Coca, M.; Connolly, A.; Convery, M.; Conway, J.; Cordelli, M.; Cranshaw, J.; Culbertson, R.; Dagenhart, D.; D'Auria, S.; de Cecco, S.; Dejongh, F.; dell'Agnello, S.; dell'Orso, M.; Demers, S.; Demortier, L.; Deninno, M.; de Pedis, D.; Derwent, P. F.; Devlin, T.; Dionisi, C.; Dittmann, J. R.; Dominguez, A.; Donati, S.; D'Onofrio, M.; Dorigo, T.; Eddy, N.; Einsweiler, K.; Engels, E.; Erbacher, R.; Errede, D.; Errede, S.; Eusebi, R.; Fan, Q.; Farrington, S.; Feild, R. G.; Fernandez, J. P.; Ferretti, C.; Field, R. D.; Fiori, I.; Flaugher, B.; Flores-Castillo, L. R.; Foster, G. W.; Franklin, M.; Freeman, J.; Friedman, J.; Fukui, Y.; Furic, I.; Galeotti, S.; Gallas, A.; Gallinaro, M.; Gao, T.; Garcia-Sciveres, M.; Garfinkel, A. F.; Gatti, P.; Gay, C.; Gerdes, D. W.; Gerstein, E.; Giagu, S.; Giannetti, P.; Giolo, K.; Giordani, M.; Giromini, P.; Glagolev, V.; Glenzinski, D.; Gold, M.; Goldschmidt, N.; Goldstein, J.; Gomez, G.; Goncharov, M.; Gorelov, I.; Goshaw, A. T.; Gotra, Y.; Goulianos, K.; Green, C.; Gresele, A.; Grim, G.; Grosso-Pilcher, C.; Guenther, M.; Guillian, G.; da Costa, J. Guimaraes; Haas, R. M.; Haber, C.; Hahn, S. R.; Halkiadakis, E.; Hall, C.; Handa, T.; Handler, R.; Happacher, F.; Hara, K.; Hardman, A. D.; Harris, R. M.; Hartmann, F.; Hatakeyama, K.; Hauser, J.; Heinrich, J.; Heiss, A.; Hennecke, M.; Herndon, M.; Hill, C.; Hocker, A.; Hoffman, K. D.; Hollebeek, R.; Holloway, L.; Hou, S.; Huffman, B. T.; Hughes, R.; Huston, J.; Huth, J.; Ikeda, H.; Issever, C.; Incandela, J.; Introzzi, G.; Iori, M.; Ivanov, A.; Iwai, J.; Iwata, Y.; Iyutin, B.; James, E.; Jones, M.; Joshi, U.; Kambara, H.; Kamon, T.; Kaneko, T.; Kang, J.; Unel, M. Karagoz; Karr, K.; Kartal, S.; Kasha, H.; Kato, Y.; Keaffaber, T. A.; Kelley, K.; Kelly, M.; Kennedy, R. D.; Kephart, R.; Khazins, D.; Kikuchi, T.; Kilminster, B.; Kim, B. J.; Kim, D. H.; Kim, H. S.; Kim, M. J.; Kim, S. B.; Kim, S. H.; Kim, T. H.; Kim, Y. K.; Kirby, M.; Kirk, M.; Kirsch, L.; Klimenko, S.; Koehn, P.; Kondo, K.; Konigsberg, J.; Korn, A.; Korytov, A.; Kotelnikov, K.; Kovacs, E.; Kroll, J.; Kruse, M.; Krutelyov, V.; Kuhlmann, S. E.; Kurino, K.; Kuwabara, T.; Kuznetsova, N.; Laasanen, A. T.; Lai, N.; Lami, S.; Lammel, S.; Lancaster, J.; Lannon, K.; Lancaster, M.; Lander, R.; Lath, A.; Latino, G.; Lecompte, T.; Le, Y.; Lee, J.; Lee, S. W.; Leonardo, N.; Leone, S.; Lewis, J. D.; Li, K.; Lin, C. S.; Lindgren, M.; Liss, T. M.; Liu, J. B.; Liu, T.; Liu, Y. C.; Litvintsev, D. O.; Lobban, O.; Lockyer, N. S.; Loginov, A.; Loken, J.; Loreti, M.; Lucchesi, D.; Lukens, P.; Lusin, S.; Lyons, L.; Lys, J.; Madrak, R.; Maeshima, K.; Maksimovic, P.; Malferrari, L.; Mangano, M.; Manca, G.; Mariotti, M.; Martignon, G.; Martin, M.; Martin, A.; Martin, V.; Martínez, M.; Matthews, J. A.; Mazzanti, P.; McFarland, K. S.; McIntyre, P.; Menguzzato, M.; Menzione, A.; Merkel, P.; Mesropian, C.; Meyer, A.; Miao, T.; Miller, R.; Miller, J. S.; Minato, H.; Miscetti, S.; Mishina, M.; Mitselmakher, G.; Miyazaki, Y.; Moggi, N.; Moore, E.; Moore, R.; Morita, Y.; Moulik, T.; Mulhearn, M.; Mukherjee, A.; Muller, T.; Munar, A.; Murat, P.; Murgia, S.; Nachtman, J.; Nagaslaev, V.; Nahn, S.; Nakada, H.; Nakano, I.; Napora, R.; Niell, F.; Nelson, C.; Nelson, T.; Neu, C.; Neubauer, M. S.; Neuberger, D.; Newman-Holmes, C.; Ngan, C. -Y. P.; Nigmanov, T.; Niu, H.; Nodulman, L.; Nomerotski, A.; Oh, S. H.; Oh, Y. D.; Ohmoto, T.; Ohsugi, T.; Oishi, R.; Okusawa, T.; Olsen, J.; Orejudos, W.; Pagliarone, C.; Palmonari, F.; Paoletti, R.; Papadimitriou, V.; Partos, D.; Patrick, J.; Pauletta, G.; Paulini, M.; Pauly, T.; Paus, C.; Pellett, D.; Penzo, A.; Pescara, L.; Phillips, T. J.; Piacentino, G.; Piedra, J.; Pitts, K. T.; Pompoš, A.; Pondrom, L.; Pope, G.; Pratt, T.; Prokoshin, F.; Proudfoot, J.; Ptohos, F.; Pukhov, O.; Punzi, G.; Rademacker, J.; Rakitine, A.; Ratnikov, F.; Ray, H.; Reher, D.; Reichold, A.; Renton, P.; Rescigno, M.; Ribon, A.; Riegler, W.; Rimondi, F.; Ristori, L.; Riveline, M.; Robertson, W. J.; Rodrigo, T.; Rolli, S.; Rosenson, L.; Roser, R.; Rossin, R.; Rott, C.; Roy, A.; Ruiz, A.; Ryan, D.; Safonov, A.; Denis, R. St.; Sakumoto, W. K.; Saltzberg, D.; Sanchez, C.; Sansoni, A.; Santi, L.; Sarkar, S.; Sato, H.; Savard, P.; Savoy-Navarro, A.; Schlabach, P.; Schmidt, E. E.; Schmidt, M. P.; Schmitt, M.; Scodellaro, L.; Scott, A.; Scribano, A.; Sedov, A.; Seidel, S.; Seiya, Y.; Semenov, A.; Semeria, F.; Shah, T.; Shapiro, M. D.; Shepard, P. F.; Shibayama, T.; Shimojima, M.; Shochet, M.; Sidoti, A.; Siegrist, J.; Sill, A.; Sinervo, P.; Singh, P.; Slaughter, A. J.; Sliwa, K.; Snider, F. D.; Snihur, R.; Solodsky, A.; Speer, T.; Spezziga, M.; Sphicas, P.; Spinella, F.; Spiropulu, M.; Spiegel, L.; Steele, J.; Stefanini, A.; Strologas, J.; Strumia, F.; Stuart, D.; Sukhanov, A.; Sumorok, K.; Suzuki, T.; Takano, T.; Takashima, R.; Takikawa, K.; Tamburello, P.; Tanaka, M.; Tannenbaum, B.; Tecchio, M.; Tesarek, R. J.; Teng, P. K.; Terashi, K.; Tether, S.; Thom, J.; Thompson, A. S.; Thomson, E.; Thurman-Keup, R.; Tipton, P.; Tkaczyk, S.; Toback, D.; Tollefson, K.; Tonelli, D.; Tonnesmann, M.; Toyoda, H.; Trischuk, W.; de Troconiz, J. F.; Tseng, J.; Tsybychev, D.; Turini, N.; Ukegawa, F.; Unverhau, T.; Vaiciulis, T.; Varganov, A.; Vataga, E.; Vejcik, S.; Velev, G.; Veramendi, G.; Vidal, R.; Vila, I.; Vilar, R.; Volobouev, I.; von der Mey, M.; Vucinic, D.; Wagner, R. G.; Wagner, R. L.; Wagner, W.; Wan, Z.; Wang, C.; Wang, M. J.; Wang, S. M.; Ward, B.; Waschke, S.; Watanabe, T.; Waters, D.; Watts, T.; Weber, M.; Wenzel, H.; Wester, W. C.; Whitehouse, B.; Wicklund, A. B.; Wicklund, E.; Wilkes, T.; Williams, H. H.; Wilson, P.; Winer, B. L.; Winn, D.; Wolbers, S.; Wolinski, D.; Wolinski, J.; Wolinski, S.; Wolter, M.; Worm, S.; Wu, X.; Würthwein, F.; Wyss, J.; Yang, U. K.; Yao, W.; Yeh, G. P.; Yeh, P.; Yi, K.; Yoh, J.; Yosef, C.; Yoshida, T.; Yu, I.; Yu, S.; Yu, Z.; Yun, J. C.; Zanello, L.; Zanetti, A.; Zetti, F.; Zucchelli, S. Bibcode: 2004PhRvL..92l1802A Altcode: 2003hep.ex....9051A We report on a search for direct Kaluza-Klein graviton production in a data sample of 84 pb-1 of pp¯ collisions at √(s)=1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and one or two high energy jets. We compare the data with the predictions from a (3+1+n)-dimensional Kaluza-Klein scenario in which gravity becomes strong at the TeV scale. At 95% confidence level (C.L.) for n=2, 4, and 6 we exclude an effective Planck scale below 1.0, 0.77, and 0.71TeV, respectively. Title: The MACHO Project Large Magellanic Cloud Variable Star Inventory. XI. Frequency Analysis of the Fundamental-Mode RR Lyrae Stars Authors: Alcock, C.; Alves, D. R.; Becker, A.; Bennett, D.; Cook, K. H.; Drake, A.; Freeman, K.; Geha, M.; Griest, K.; Kovács, G.; Lehner, M.; Marshall, S.; Minniti, D.; Nelson, C.; Peterson, B.; Popowski, P.; Pratt, M.; Quinn, P.; Rodgers, A.; Stubbs, C.; Sutherland, W.; Vandehei, T.; Welch, D. L. Bibcode: 2003ApJ...598..597A Altcode: 2003astro.ph..8019A We have frequency-analyzed 6391 variables classified earlier as fundamental-mode RR Lyrae (RR0) stars in the MACHO database on the Large Magellanic Cloud (LMC). The overwhelming majority (i.e., 96%) of these variables have been proved to be indeed RR0 stars, whereas the remaining ones have fallen into one of the following categories: single- and double-mode Cepheids, binaries, first-overtone and double-mode RR Lyrae stars, and nonclassified variables. Special attention has been paid to the properties of the amplitude- and phase-modulated RR0 stars (the Blazhko stars). We found altogether 731 Blazhko variables showing either a doublet or an equidistant triplet pattern at the main pulsation component in their frequency spectra. This sample overwhelmingly exceeds the number of Blazhko stars known in all other systems combined. The incidence rate of the Blazhko variables among the RR0 stars in the LMC is 11.9%, which is 3 times higher than their rate among the first-overtone RR Lyrae stars. No difference is found in the average brightness between the single-mode and Blazhko variables. However, the latter ones show a somewhat lower degree of skewness in their average light curves and a concomitant lower total amplitude in their modulation-free light curves. From the frequency spectra we found that variables with larger modulation amplitudes at the higher frequency side of the main pulsation component are 3 times more common than the ones showing the opposite amplitude pattern. A search for a modulation component with the Blazhko period in the average brightness of the individual variables showed the existence of such a modulation with an overall amplitude of ~0.006 mag. On the other hand, a similar search for quadruple modulation patterns around the main pulsation component has failed to clearly detect such components at the ~0.004 mag level. This means that the amplitudes of the quadruple components (if they exist) should be, on average, at least 10 times smaller than those of the triplet components. This finding and the existence of Blazhko variables with highly asymmetric modulation amplitudes not only question the validity of the magnetic oblique rotator model but also put stringent constraints on models based on mode-coupling theories. Title: [OIII] Emission Line Profiles in PG Quasars Authors: Nelson, C.; Gelderman, R.; Plasek, A.; Thompson, A.; Monroe, T.; Lamb, D. A. Bibcode: 2002AAS...20111404N Altcode: 2002BAAS...34.1286N We have obtained high S/N, high resolution profiles of the [OIII] λ 5007 emission line for nearly all of the PG quasars.Previous studies have shown that the kinematics of the narrow line region gas (NLR) in active galaxies are predominantly due to gravitational motion in the host bulge potential. Thus, using the now well established correlation between bulge velocity dispersion, σ , and nuclear black hole mass, M , we can use the widths of the [OIII] line profiles to estimate M for the entire sample. These values are independent of results from reverberation mapping techniques which rely on the assumption of Keplerian motion in the broad line region. The M values can be used to estimate the Eddington ratio, and to test the idea that L/LE is the primary influence on the group of AGN correlations known as eigenvector 1. We present the preliminary results of our analysis in this poster. This project has been supported by the Iowa Space Grant Consortium. Title: Frequency Analysis of a Subset of Fundamental Mode RR Lyrae Stars from the MACHO Project Large Magellanic Cloud Database Authors: Welch, D. L.; Kovács, G.; Cook, K. H.; Alcock, C.; Allsman, R.; Alves, D. R.; Axelrod, T.; Becker, A.; Bennett, D.; Drake, A.; Freeman, K.; Geha, M.; Griest, K.; Lehner, M.; Marshall, S.; Minniti, D.; Nelson, C.; Peterson, B.; Popowski, P.; Pratt, M.; Quinn, P.; Rodgers, A.; Stubbs, C.; Sutherland, W.; Vandehei, T.; MACHO Collaboration Bibcode: 2002ASPC..259..412W Altcode: 2002IAUCo.185..412W; 2002rnpp.conf..412W No abstract at ADS Title: Mass-losing Semiregular Variable Stars in Baade's Windows Authors: Alard, C.; Blommaert, J. A. D. L.; Cesarsky, C.; Epchtein, N.; Felli, M.; Fouque, P.; Ganesh, S.; Genzel, R.; Gilmore, G.; Glass, I. S.; Habing, H.; Omont, A.; Perault, M.; Price, S.; Robin, A.; Schultheis, M.; Simon, G.; van Loon, J. Th.; Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Geha, M.; Griest, K.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Nelson, C.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Quinn, P. J.; Sutherland, W.; Tomaney, A. B.; Vandehei, T.; Welch, D. L. Bibcode: 2001ApJ...552..289A Altcode: 2001astro.ph..1094A By cross-correlating the results of two recent large-scale surveys, the general properties of a well-defined sample of semiregular variable stars have been determined. ISOGAL mid-infrared photometry (7 and 15 μm) and MACHO V and R light curves are assembled for approximately 300 stars in the Baade's windows of low extinction toward the Galactic bulge. These stars are mainly giants of late M spectral type, evolving along the asymptotic giant branch (AGB). They are found to possess a wide and continuous distribution of pulsation periods and to obey an approximate logP-Mbol relation or set of such relations. Approximate mass-loss rates M in the range of ~1×10-8 to 5×10-7 Msolar yr-1 are derived from ISOGAL mid-infrared photometry and models of stellar spectra adjusted for the presence of optically thin circumstellar silicate dust. Mass-loss rates depend on luminosity and pulsation period. Some stars lose mass as rapidly as short-period Mira variables but do not show Mira-like amplitudes. A period of 70 days or longer is a necessary but not sufficient condition for mass loss to occur. For AGB stars in the mass-loss ranges that we observe, the functional dependence of mass-loss rate on temperature and luminosity can be expressed as M~TαLβ, where α=-8.80+0.96-0.24 and β=+1.74+0.16-0.24, in agreement with recent theoretical predictions. If we include our mass-loss rates with a sample of extreme mass-losing AGB stars in the Large Magellanic Cloud and ignore T as a variable, we get the general result for AGB stars that M~L2.7, valid for AGB stars with 10-8<M<10-4 Msolar yr-1. Title: The Nuclear Dynamics of M32. I. Data and Stellar Kinematics Authors: Joseph, C. L.; Merritt, D.; Olling, R.; Valluri, M.; Bender, R.; Bower, G.; Danks, A.; Gull, T.; Hutchings, J.; Kaiser, M. E.; Maran, S.; Weistrop, D.; Woodgate, B.; Malumuth, E.; Nelson, C.; Plait, P.; Lindler, D. Bibcode: 2001ApJ...550..668J Altcode: 2000astro.ph..5530J We have obtained optical long-slit spectroscopy of the nucleus of M32 using the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. The stellar rotation velocity and velocity dispersion, as well as the full line-of-sight velocity distribution (LOSVD), were determined as a function of position along the slit using two independent spectral deconvolution algorithms. We see three clear kinematical signatures of the nuclear black hole: a sudden upturn, at ~0.3" from the center, in the stellar velocity dispersions; a flat or rising rotation curve into the center; and strong, non-Gaussian wings on the central LOSVD. The central velocity dispersion is ~130 km s-1 (Gaussian fit) or >~175 km s-1 (corrected for the wings). The central kinematics are consistent with the presence of a supermassive compact object in M32 with a mass in the range (2-4)×106 Msolar. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555. Title: Evidence of a Supermassive Black Hole in the Galaxy NGC 1023 from the Nuclear Stellar Dynamics Authors: Bower, G. A.; Green, R. F.; Bender, R.; Gebhardt, K.; Lauer, T. R.; Magorrian, J.; Richstone, D. O.; Danks, A.; Gull, T.; Hutchings, J.; Joseph, C.; Kaiser, M. E.; Weistrop, D.; Woodgate, B.; Nelson, C.; Malumuth, E. M. Bibcode: 2001ApJ...550...75B Altcode: 2000astro.ph.11204B We analyze the nuclear stellar dynamics of the SB0 galaxy NGC 1023, utilizing observational data both from the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope and from the ground. The stellar kinematics measured from these long-slit spectra show rapid rotation (V~70 km s-1 at a distance of 0.1"=4.9 pc from the nucleus) and increasing velocity dispersion toward the nucleus (where σ=295+/-30 km s-1). We model the observed stellar kinematics assuming an axisymmetric mass distribution with both two and three integrals of motion. Both modeling techniques point to the presence of a central dark compact mass (which presumably is a supermassive black hole) with confidence greater than 99%. The isotropic two-integral models yield a best-fitting black hole mass of (6.0+/-1.4)×107 Msolar and mass-to-light ratio (M/LV) of 5.38+/-0.08, and the goodness of fit (χ2) is insensitive to reasonable values for the galaxy's inclination. The three-integral models, which nonparametrically fit the observed line-of-sight velocity distribution as a function of position in the galaxy, suggest a black hole mass of (3.9+/-0.4)×107 Msolar and M/LV of 5.56+/-0.02 (internal errors), and the edge-on models are vastly superior fits over models at other inclinations. The internal dynamics in NGC 1023 as suggested by our best-fit three-integral model shows that the velocity distribution function at the nucleus is tangentially anisotropic, suggesting the presence of a nuclear stellar disk. The nuclear line-of-sight velocity distribution has enhanced wings at velocities >=600 km s-1 from systemic, suggesting that perhaps we have detected a group of stars very close to the central dark mass. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under NASA contract NAS 5-26555. Title: MACHO Bulge Microlensing: Spectroscopy Needed Authors: Minniti, D.; Alcock, C.; Cook, K.; Geha, M.; Marshall, S.; Nelson, C.; Popowski, P.; Axelrod, T.; Allsman, R.; Drake, A.; Freeman, K. C.; Peterson, B.; Becker, A.; Pratt, M.; Stubbs, C.; Tomaney, A.; Alves, D. R.; Bennett, D.; Quinn, P.; Welch, D.; Sutherland, W. Bibcode: 2001ASPC..230...39M Altcode: 2001gddg.conf...39M We discuss the analysis of MACHO bulge microlensing. New results that give a smaller optical depth [τ = (2-3) 10-6] are encouragingly closer to current models of the inner Milky Way. Although hundreds of bulge events are now available and much progress has occurred, there is still a need for spectroscopic characterization of the microlensing events. Title: HST Observations of IRAS 15179+3956, an Interacting Galaxy Pair in the Bootes Void Authors: Cruzen, S.; Wehr, T.; Weistrop, D.; Nelson, C.; Angione, R. Bibcode: 2000AAS...197.7904C Altcode: 2000BAAS...32.1532C We present analysis of broadband (U, V, I) images of the asymmetric Bootes Void galaxy IRAS 15179+3956, taken with the Hubble Space Telescope's WFPC2 camera. We also include a discussion of optical spectroscopy from Mount Laguna Observatory. Ground-based optical (Cruzen, et. al. 1997) and radio observations (Sage et. al. 1997) have suggested that this system is an interacting pair. It exhibits very blue broadband colors, a strong emission-line spectrum, and is reported to be an OH megamaser (Bottinelli, et. al. 1989, Baan et. al. 1998), all suggesting violent star formation. Our WFPC2 images clearly confirm that this system is an interacting pair, with the southern-most galaxy exhibiting a greatly disturbed morphology and an extended tidal tail. The broadband colors identify regions of enhanced star-formation within the two galaxies. The starburst models of Leitherer et al. (1999) are compared with the colors and equivalent widths of emission lines to place constraints on the age of the star-formation episodes. We describe the morphologies of both galaxies and discuss the effects of the tidal interaction. The cosmological implications of interacting galaxies in low-density environments are also discussed. This work has been supported in part by NASA under contract NAS5-31231, and through the Nevada Space Grant Consortium. Mount Laguna Observatory is operated jointly by San Diego State University and the University of Illinois. Title: The MACHO Project Large Magellanic Cloud Variable-Star Inventory. IX. Frequency Analysis of the First-Overtone RR Lyrae Stars and the Indication for Nonradial Pulsations Authors: Alcock, C.; Allsman, R.; Alves, D. R.; Axelrod, T.; Becker, A.; Bennett, D.; Clement, C.; Cook, K. H.; Drake, A.; Freeman, K.; Geha, M.; Griest, K.; Kovács, G.; Kurtz, D. W.; Lehner, M.; Marshall, S.; Minniti, D.; Nelson, C.; Peterson, B.; Popowski, P.; Pratt, M.; Quinn, P.; Rodgers, A.; Rowe, J.; Stubbs, C.; Sutherland, W.; Tomaney, A.; Vandehei, T.; Welch, D. L. Bibcode: 2000ApJ...542..257A Altcode: 2000astro.ph..5361A More than 1300 variables classified provisionally as first-overtone RR Lyrae pulsators in the MACHO variable-star database of the Large Magellanic Cloud (LMC) have been subjected to standard frequency analysis. Based on the remnant power in the prewhitened spectra, we found 70% of the total population to be monoperiodic. The remaining 30% (411 stars) are classified as one of nine types according to their frequency spectra. Several types of RR Lyrae pulsational behavior are clearly identified here for the first time. Together with the earlier discovered double-mode (fundamental and first-overtone) variables, this study increased the number of known double-mode stars in the LMC to 181. During the total 6.5 yr time span of the data, 10% of the stars showed strong period changes. The size, and in general also the patterns of the period changes, exclude a simple evolutionary explanation. We also discovered two additional types of multifrequency pulsators with low occurrence rates of 2% for each. In the first type, there remains one closely spaced component after prewhitening by the main pulsation frequency. In the second type, the number of remnant components is two; they are also closely spaced, and are symmetric in their frequency spacing relative to the central component. This latter type of variables are associated with their relatives among the fundamental pulsators, known as Blazhko variables. Their high frequency (~20%) among the fundamental-mode variables versus the low occurrence rate of their first-overtone counterparts makes it more difficult to explain the Blazhko phenomenon by any theory depending mainly on the role of aspect angle or magnetic field. None of the current theoretical models are able to explain the observed close frequency components without invoking nonradial pulsation components in these stars. Title: Binary Microlensing Events from the MACHO Project Authors: Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Baines, D.; Becker, A. C.; Bennett, D. P.; Bourke, A.; Brakel, A.; Cook, K. H.; Crook, B.; Crouch, A.; Dan, J.; Drake, A. J.; Fragile, P. C.; Freeman, K. C.; Gal-Yam, A.; Geha, M.; Gray, J.; Griest, K.; Gurtierrez, A.; Heller, A.; Howard, J.; Johnson, B. R.; Kaspi, S.; Keane, M.; Kovo, O.; Leach, C.; Leach, T.; Leibowitz, E. M.; Lehner, M. J.; Lipkin, Y.; Maoz, D.; Marshall, S. L.; McDowell, D.; McKeown, S.; Mendelson, H.; Messenger, B.; Minniti, D.; Nelson, C.; Peterson, B. A.; Popowski, P.; Pozza, E.; Purcell, P.; Pratt, M. R.; Quinn, J.; Quinn, P. J.; Rhie, S. H.; Rodgers, A. W.; Salmon, A.; Shemmer, O.; Stetson, P.; Stubbs, C. W.; Sutherland, W.; Thomson, S.; Tomaney, A.; Vandehei, T.; Walker, A.; Ward, K.; Wyper, G. Bibcode: 2000ApJ...541..270A Altcode: 1999astro.ph..7369M We present the light curves of 21 gravitational microlensing events from the first six years of the MACHO Project gravitational microlensing survey that are likely examples of lensing by binary systems. These events were manually selected from a total sample of ~350 candidate microlensing events that were either detected by the MACHO Alert System or discovered through retrospective analyses of the MACHO database. At least 14 of these 21 events exhibit strong (caustic) features, and four of the events are well fit with lensing by large mass ratio (brown dwarf or planetary) systems, although these fits are not necessarily unique. The total binary event rate is roughly consistent with predictions based upon our knowledge of the properties of binary stars, but a precise comparison cannot be made without a determination of our binary lens event detection efficiency. Toward the Galactic bulge, we find a ratio of caustic crossing to noncaustic crossing binary lensing events of 12:4, excluding one event for which we present two fits. This suggests significant incompleteness in our ability to detect and characterize noncaustic crossing binary lensing. The distribution of mass ratios, N(q), for these binary lenses appears relatively flat. We are also able to reliably measure source-face crossing times in four of the bulge caustic crossing events, and recover from them a distribution of lens proper motions, masses, and distances consistent with a population of Galactic bulge lenses at a distance of 7+/-1 kpc. This analysis yields two systems with companions of ~0.05 Msolar. Title: The MACHO Project Sample of Galactic Bulge High-Amplitude δ Scuti Stars: Pulsation Behavior and Stellar Properties Authors: Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Geha, M.; Griest, K.; Lehner, M. J.; Marshall, S. L.; McNamara, B. J.; Minniti, D.; Nelson, C.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Sutherland, W.; Templeton, M. R.; Vandehei, T.; Welch, D. L. Bibcode: 2000ApJ...536..798A Altcode: We have detected 90 objects with periods and light-curve structures similar to those of field δ Scuti stars using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude δ Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground δ Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population δ Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field δ Scuti stars and the δ Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude δ Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles day-1) and the observed period ratios of ~0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes. Title: The Ionization Source in the Nucleus of M84 Authors: Bower, G. A.; Green, R. F.; Quillen, A. C.; Danks, A.; Gull, T.; Hutchings, J.; Joseph, C.; Kaiser, M. E.; Weistrop, D.; Woodgate, B.; Malumuth, E. M.; Nelson, C. Bibcode: 2000ApJ...534..189B Altcode: 1999astro.ph.12393B We have obtained new Hubble Space Telescope observations of M84, a nearby massive elliptical galaxy whose nucleus contains a ~1.5×109 Msolar dark compact object, which presumably is a supermassive black hole. Our Space Telescope Imaging Spectrograph spectrum provides the first clear detection of emission lines in the blue (e.g., [O II] λ3727, Hβ, and [O III] λλ4959, 5007), which arise from a compact region ~0.28" across centered on the nucleus. Our Near-Infrared Camera and Multiobject Spectrometer images exhibit the best view through the prominent dust lanes evident at optical wavelengths and provide a more accurate correction for the internal extinction. The relative fluxes of the emission lines we have detected in the blue together with those recently detected in the wavelength range 6295-6867 Å by Bower et al. indicate that the gas at the nucleus is photoionized by a nonstellar process instead of hot stars. Stellar absorption features from cool stars at the nucleus are very weak. We update the spectral energy distribution of the nuclear point source and find that although it is roughly flat in most bands, the optical-to-UV continuum is very red, similar to the spectral energy distribution of BL Lac. Thus, the nuclear point source seen in high-resolution optical images by Bower et al. is not a star cluster but is instead a nonstellar source. Assuming isotropic emission from this source, we estimate that the ratio of bolometric luminosity to Eddington luminosity is ~5×10-7. However, this could be underestimated if this source is a misaligned BL Lac object, which is a possibility suggested by the spectral energy distribution and the evidence of optical variability we describe. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555. Title: Frequency Analysis of the RRc Variables of the MACHO Database for the LMC Authors: Kovács, G.; Alcock, C.; Allsman, R.; Alves, D.; Axelrod, T.; Becker, A.; Bennett, D.; Clement, C.; Cook, K. H.; Drake, A.; Freeman, K.; Geha, M.; Griest, K.; Kurtz, D. W.; Lehner, M.; Marshall, S.; Minniti, D.; Nelson, C.; Peterson, B.; Popowski, P.; Pratt, M.; Quinn, P.; Rodgers, A.; Rowe, J.; Stubbs, C.; Sutherland, W.; Tomaney, A.; Vandehei, T.; Welch, D. L.; MACHO Collaboration Bibcode: 2000ASPC..203..313K Altcode: 2000ilss.conf..313K; 2000IAUCo.176..313K We present the first massive frequency analysis of the 1200 first overtone RR Lyrae stars in the Large Magellanic Cloud observed in the first 4.3 yr of the MACHO project. Besides the many new double-mode variables, we also discovered stars with closely spaced frequencies. These variables are most probably nonradial pulsators. Title: Kinematics and Dynamics of the Narrow Line Region of NGC4151 Authors: Kaiser, M. E.; Bradley, L. D., II; Hutchings, J. B.; Weistrop, D.; Nelson, C.; Kraemer, S. B.; Crenshaw, D. M.; Ruiz, J.; Gull, T. R. Bibcode: 1999ASPC..182...51K Altcode: 1999gady.conf...51K No abstract at ADS Title: Kinematic Mapping of the Narrow Line Region of NGC4151 Authors: Kaiser, Mary E.; Bradley, L. D., II; Hutchings, J. B.; Kraemer, S. B.; Crenshaw, D. M.; Ruiz, J.; Weistrop, D.; Nelson, C.; Gull, T. R. Bibcode: 1999IAUS..194...79K Altcode: No abstract at ADS Title: Spatially Resolved Spectra of 3C Galaxy Nuclei Authors: Hutchings, J. B.; Baum, S. A.; Weistrop, D.; Nelson, C.; Kaiser, M. E.; Gelderman, R. F. Bibcode: 1998AJ....116..634H Altcode: 1998astro.ph..5177H We present and discuss visible-wavelength long-slit spectra of four low-redshift 3C galaxies obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST). The slit was aligned with near-nuclear jetlike structure seen in HST images of the galaxies, to give unprecedented spatial resolution of their inner regions. In 3C 135 and 3C 171, the spectra reveal clumpy emission-line structures that indicate outward motions of a few hundred kilometers per second within a centrally illuminated and ionized biconical region. There may also be some low-ionization, high-velocity material associated with 3C 135. In 3C 264 and 3C 78, the jets have blue featureless spectra consistent with their proposed synchrotron origin. There is weak associated line emission in the innermost part of the jets with mild outflow velocity. These jets are bright and highly collimated only within a circumnuclear region of lower galaxy luminosity, which is not dusty. We discuss the origins of these central regions and their connection with relativistic jets. Title: The MACHO Project: Status Report on the Magellanic Clouds. Authors: Vandehei, T.; Griest, K.; Alcock, C.; Alves, D.; Cook, K.; Minniti, D.; Marshall, S.; Allsman, R.; Axelrod, T.; Freeman, K.; Peterson, B.; Rodgers, A.; Pratt, M.; Becker, A.; Stubbs, C.; Tomaney, A. B.; Lehner, M.; Bennett, D.; Nelson, C.; Quinn, P.; Sutherland, W.; Welch, D. Bibcode: 1998AAS...192.0703V Altcode: 1998BAAS...30..825V The MACHO Project is a search for dark matter in the form of massive compact halo objects (MACHOs). Photometric monitoring of tens of millions of stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and Galactic bulge is used to search for these rare gravitational microlensing events caused by these otherwise invisible objects. An analysis of 4 years of LMC data on 12 million stars and 5 years of SMC data on 3 million stars is currently underway. We present preliminary results of this analysis which reveal about 15 candidate microlensing events in the LMC and 1 event in the SMC. We also present our microlensing detection efficiency calculation pipeline. The accurate determination of our detection efficiency is key in estimating the MACHO contribution to the dark matter in the halo. The efficiency pipeline uses data from the MACHO Project's ground based survey and from HST observations of MACHO fields to determine the true color and luminosity distribution of LMC source stars. Artificial microlensing events are then inserted into the underlying source distribution, image sequences are created from a wide sample of real image conditions and detection efficiencies are determined using our standard reduction pipeline. The full calculation of our efficiencies requires the creation, reduction and analysis of 322 Gbytes of artificial image data and is currently underway. Title: Long-Slit Spectroscopy of the Star-forming Regions in the Interacting Galaxies NGC 3991, NGC 3994 and NGC 3995 Authors: Nelson, C.; Weistrop, D.; Angione, R. Bibcode: 1998AAS...192.6912N Altcode: 1998BAAS...30..925N We have obtained long-slit spectroscopy with the Kitt Peak 2.1-meter telescope of the interacting galaxies NGC 3991, NGC 3994 and NGC 3995 to study how star formation propagates in tidally disturbed systems. UBVR imaging of these galaxies has shown they contain bright, blue star-forming knots, with a range of ages and reddening. Our apertures were chosen to examine a number of these knots in various galaxy environments. Preliminary analysis of the spectra reveals evidence for population differences through a variety of emission and absorption features of varying strengths. The strength of the nebular emission lines confirms that many regions are undergoing high rates of star formation. These data will used to determine the age of each knot as a function of location in the galaxy, to address a series of questions. Does the star formation occur first in the nucleus or outer regions of the galaxies? Are there differences in the stellar populations of the star forming regions related to the local gas density, disk dynamics, or other environmental factors? Does star formation triggered by galaxy interactions produce an initial mass function biased toward massive stars? These results are part of an ongoing study of star formation in interacting galaxies that will include HST imaging and spectroscopy with the Space Telescope Imaging Spectrograph. This research has been supported in part by NASA, under contract NAS5-31231. Title: Long-slit Spectroscopy of the Star-forming Regions in the Interacting Galaxies NGC 3395/3396 Authors: Weistrop, D.; Nelson, C.; Angione, R. Bibcode: 1998AAS...192.6911W Altcode: 1998BAAS...30Q.925W We have obtained long-slit spectroscopy of the interacting galaxies NGC 3395, NGC 3396 to investigate the propagation of star formation in tidally disturbed systems. UBVR imaging of these galaxies has shown that they contain bright, blue star-forming knots, with a range of ages and reddening. The NOAO 2.1 meter telescope was used to obtain spectroscopy of several of the knots in various galaxy environments. Preliminary analysis of the spectra reveals a variety of emission and absorption features of varying strengths, defining population differences across the galaxies. The strength of the nebular emission lines confirms that regions undergoing high rates of star formation are present. These data will be used to investigate the amount of reddening in the knots, and to determine the ages of the youngest stars as a function of location in the galaxy. Questions to be addressed include: Does the star formation occur first in the nucleus or outer regions of the galaxies? Are there differences in the stellar populations of the star forming regions related to the local gas density, disk dynamics, or other environmental factors? Does star formation triggered by galaxy interactions produce an initial mass function biased toward massive stars? These results are part of an ongoing study of star formation in interacting galaxies that will include HST imaging and spectroscopy with the Space Telescope Imaging Spectrograph. This research has been supported in part by NASA, under contract NAS5-31231. Title: Characterization of Magnetite Within Carbonate in ALH 84001 Authors: Blake, D. F.; Treiman, A. H.; Cady, S.; Nelson, C.; Krishnan, K. Bibcode: 1998LPI....29.1347B Altcode: No abstract at ADS Title: An improved, optically-pumped, primary frequency standard. Authors: Hasegawa, A.; Fukuda, K.; Kotake, N.; Kajita, M.; Morikawa, T.; Lee, W. D.; Nelson, C.; Jennings, D. A.; Mullen, L.; Shiriey, J. H.; Drullinger, R. Bibcode: 1998pemd.conf..177H Altcode: An improved primary frequency standard based on an optically-pumped, thermal, atomic-beam has been jointly developed by CRL and NIST. The design details along with the first evaluation and comparison with NIST's existing standard are presented. Title: The MACHO Project: Preliminary Results from 4 years of LMC observations. Authors: Cook, K.; Alcock, C.; Alves, D.; Minniti, D.; Marshall, S.; Vandehei, T.; Griest, K.; Allsman, R.; Axelrod, T.; Freeman, K.; Peterson, B.; Rodgers, A.; Pratt, M.; Becker, A.; Stubbs, C.; Tomaney, A.; Lehner, M.; Bennett, D.; Nelson, C.; Quinn, P.; Sutherland, W.; Welch, D. Bibcode: 1997AAS...191.8301C Altcode: 1997BAAS...29.1346C The MACHO Project is a search for dark matter in the form of massive compact halo objects (MACHOs). Photometric monitoring of tens of millions of stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and Galactic bulge is used to search for gravitational microlensing events caused by these otherwise invisible objects. An analysis of 4 years of LMC data on 12.5 million stars is currently underway. We present preliminary results of this analysis which reveal about 15 candidate microlensing events. We also present our microlensing detection efficiency calculation pipeline. The accurate determination of our detection efficiency is key in estimating the MACHO contribution to the dark matter halo. The efficiency pipeline uses data from the MACHO Project's ground based survey and from HST observations of MACHO fields to determine the true color and luminosity distribution of LMC source stars. Artificial microlensing events are then inserted into the underlying source distribution, image sequences are created from a wide sample of real image conditions and detection efficiencies are determined using our standard reduction pipeline. The full calculation of our efficiencies requires the creation, reduction and analysis of 322 Gbytes of artificial image data and is currently underway. The MACHO Project dedicates this work to one of its key founders, Alex Rodgers. Title: The MACHO Project 9 Million Star Color-Magnitude Diagram of the Large Magellanic Cloud Bar Authors: Alves, D.; Alcock, C.; Cook, K.; Marshall, S.; Minniti, D.; Allsman, R.; Axelrod, T.; Freeman, K.; Peterson, B.; Rodgers, A.; Becker, A.; Stubbs, C.; Tomaney, A.; Griest, K.; Vandehei, T.; Bennett, D.; Lehner, M.; Nelson, C.; Pratt, M.; Quinn, P.; Sutherland, W.; Welch, D. Bibcode: 1997AAS...19111501A Altcode: 1997BAAS...29.1398A We present a composite 9 million star color-magnitude diagram (9M CMD) of the LMC bar using calibrated MACHO project photometry. The large number of stars reveal numerous low-level features, many of which can be attributed to short-lived stages of stellar evolution. The star formation and chemical enrichment history of the LMC is investigated, with additional discussion of the ~ 10(5) LMC variable stars in the MACHO database. Example features are intermediate mass supergiant sequences, multiple sequences of AGB stars, a bump on the RGB, and possible evidence for extended HB evolution. The 9M CMD is interpreted with theoretical isochrones, CMDs of LMC clusters, an HST CMD, and artificial CMDs. The latter include the effects of differential reddening and blending. The intermediate mass supergiants, including Cepheids, suggest a variable recent star formation history. The RGB and multiple AGB sequences are consistent with two superposed populations; an ancient population with [Fe/H] ~ -1.6 dex, and a few Gyr-old population with [Fe/H] ~ -0.7 dex. The location of the bump on the RGB constrains the age and metallicity of the younger population; no other RGB bump is observed. The possibility of an intervening stellar population in the Galactic halo is probed with the 9M CMD and archival data. Galactic star count model predictions agree well with foreground stars observed in the 9M CMD. We predict the planetary nebulae and carbon stars associated with an hypothetical intervening population. Lastly, we discuss the 9M CMD and MACHO microlensing detection efficiencies. Alves dedicates this paper to Alex Rodgers, who greatly influenced this work and will be fondly remembered.