Browsing by Subject "white-dwarfs"
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Item A Catalog Of Near-Infrared Spectra From Type Ia Supernovae(2009-09) Marion, G. H.; Hoflich, P.; Gerardy, C. L.; Vacca, W. D.; Wheeler, J. C.; Robinson, E. L.; Marion, G. H.; Robinson, E. L.We present 41 near-infrared (NIR, 0.7-2.5 mu m) spectra from normal Type Ia supernovae (SNe Ia) obtained at epochs ranging from 14 days before to 75 days with respect to the maximum light date in the V band. All data were obtained at the Infrared Telescope Facility using the SpeX instrument. We identify many spectral features, measure the Doppler velocities, and discuss the chemical distribution of explosion products in SNe Ia. We describe procedures for smoothing data, fitting continua, and measuring absorption features to ensure consistency for measurement and analysis. This sample provides the first opportunity to examine and compare a large number of SNe Ia in this wavelength region. NIR data are a rich source of information about explosion products whose signatures are blended or obscured in other spectral regions and NIR observations probe a greater radial depth than optical wavelengths. We analyze similarities and differences in the spectra and we show that the progressive development of spectral features for normal SNe Ia in the NIR is consistent with time. We confirm the presence of O I, Mg II, Ca II, Si II, Fe II, and Co II in these SNe. Possible identifications are made for S I, Si III, Mn II, and Fe III. There is no evidence in these data for H I, He I, C I, or C II. As the explosion products expand and cool, progressively deeper layers are revealed. Thus, a time sequence of spectra examines the chemical structure and provides direct evidence of the physical properties of SNe Ia from the outer layers to deep inside the SN. Measured Doppler velocities indicate that burning products in SNe Ia are distributed in distinct layers with no large-scale mixing. Carbon is not detected in these data, in agreement with previous results with NIR data establishing very low limits on carbon abundance in SNe Ia. Carbon burning products, O and Mg, are plentiful in the outer layers suggesting that the entire progenitor is burned in the explosion. The data provide a resource for investigations of cross-correlations with other data libraries that may further constrain SN Ia physics and improve the effectiveness of SNe Ia as cosmological distance indicators.Item A Deep Proper Motion Catalog Within The Sloan Digital Sky Survey Footprint(2014-12) Munn, Jeffrey A.; Harris, Hugh C.; von Hippel, Ted; Kilic, Mukremin; Liebert, James W.; Williams, Kurtis A.; DeGenarro, Steven; Jeffery, Elizabeth; Tilleman, Trudy M.; DeGenarro, StevenA new proper motion catalog is presented, combining the Sloan Digital Sky Survey (SDSS) with second epoch observations in the r band within a portion of the SDSS imaging footprint. The new observations were obtained with the 90prime camera on the Steward Observatory Bok 90 inch telescope, and the Array Camera on the U.S. Naval Observatory, Flagstaff Station, 1.3 m telescope. The catalog covers 1098 square degrees to r = 22.0, an additional 1521 square degrees to r - 20.9, plus a further 488 square degrees of lesser quality data. Statistical errors in the proper motions range from 5 mas year(-1) at the bright end to 15 mas year(-1) at the faint end, for a typical epoch difference of six years. Systematic errors are estimated to be roughly 1 mas year(-1) for the Array Camera data, and as much as 2-4 mas year(-1) for the 90prime data (though typically less). The catalog also includes a second epoch of r band photometry.Item Discovery Of A New AM CVn System With The Kepler Satellite(2011-01) Fontaine, G.; Brassard, P.; Green, E. M.; Charpinet, S.; Dufour, Patrick; Hubeny, I.; Steeghs, D.; Aerts, C.; Randall, S. K.; Bergeron, P.; Guvenen, B.; O'Malley, C. J.; Van Grootel, V.; Ostensen, R. H.; Bloemen, S.; Silvotti, R.; Howell, Steve B.; Baran, A.; Kepler, S. O.; Marsh, T. R.; Montgomery, Michael H.; Oreiro, R.; Provencal, J.; Telting, J.; Winget, D. E.; Zima, W.; Christensen-Dalsgaard, J.; Kjeldsen, H.; Montgomery, Michael H.We report the discovery of a new AM CVn system on the basis of broadband photometry obtained with the Kepler satellite supplemented by ground-based optical spectroscopy. Initially retained on Kepler target lists as a potential compact pulsator, the blue object SDSS J190817.07+394036.4 (KIC 004547333) has turned out to be a high-StateAM CVn star showing the He-dominated spectrum of its accretion disk significantly reddened by interstellar absorption. We constructed new grids of NLTE synthetic spectra for accretion disks in order to analyze our spectroscopic observations. From this analysis, we infer preliminary estimates of the rate of mass transfer, the inclination angle of the disk, and the distance to the system. The AM CVn nature of the system is also evident in the Kepler light curve, from which we extracted 11 secure periodicities. The luminosity variations are dominated by a basic periodicity of 938.507 s, likely to correspond to a superhump modulation. The light curve folded on the period of 938.507 s exhibits a pulse shape that is very similar to the superhump wavefront seen in AM CVn itself, which is a high-Statesystem and the prototype of the class. Our Fourier analysis also suggests the likely presence of a quasi-periodic oscillation similar to those already observed in some high-StateAM CVn systems. Furthermore, some very low-frequency, low-amplitude aperiodic photometric activity is likely present, which is in line with what is expected in accreting binary systems. Inspired by previous work, we further looked for and found some intriguing numerical relationships between the 11 secure detected frequencies, in the sense that we can account for all of them in terms of only three basic clocks. This is further evidence in favor of the AM CVn nature of the system.Item Do Hydrogen-Deficient Carbon Stars Have Winds?(2009-06) Geballe, T. R.; Rao, N. Kameswara; Clayton, Geoffrey C.; Rao, N. KameswaraWe present high resolution spectra of the five known hydrogen-deficient carbon (HdC) stars in the vicinity of the 10830 angstrom line of neutral helium. In R Coronae Borealis (RCB) stars the He I line is known to be strong and broad, often with a P Cygni profile, and must be formed in the powerful winds of those stars. RCB stars have similar chemical abundances as HdC stars and also share greatly enhanced O-18 abundances with them, indicating a common origin for these two classes of stars, which has been suggested to be white dwarf mergers. A narrow He I absorption line may be present in the hotter HdC stars, but no line is seen in the cooler stars, and no evidence for a wind is found in any of them. The presence of wind lines in the RCB stars is strongly correlated with dust formation episodes so the absence of wind lines in the HdC stars, which do not make dust, is as expected.Item The Effect Of Turbulent Intermittency On The Deflagration To Detonation Transition In Supernova Ia Explosions(2008-07) Pan, Lubin; Wheeler, J. Craig; Scalo, John; Pan, Lubin; Wheeler, J. Craig; Scalo, JohnWe examine the effects of turbulent intermittency on the deflagration to detonation transition (DDT) in Type Ia supernovae. The Zel'dovich mechanism for DDT requires the formation of a nearly isothermal region of mixed ash and fuel that is larger than a critical size. We primarily consider the hypothesis by Khokhlov et al. and Niemeyer and Woosley that the nearly isothermal, mixed region is produced when the flame makes the transition to the distributed regime. We use two models for the distribution of the turbulent velocity fluctuations to estimate the probability as a function of the density in the exploding white dwarf that a given region of critical size is in the distributed regime due to strong local turbulent stretching of the flame structure. We also estimate lower limits on the number of such regions as a function of density. We find that the distributed regime, and hence perhaps DDT, occurs in a local region of critical size at a density at least a factor of 2-3 larger than predicted for mean conditions that neglect intermittency. This factor makes the transition density much larger than the empirical value from observations in most situations. We also consider the intermittency effect on the more stringent conditions for DDT by Lisewski et al. and Woosley. We find that a turbulent velocity of 10(8) cm s(-1) in a region of size 10(6) cm, as required by Lisewski et al., is rare. We expect that intermittency has a weaker effect on the Woosley model with a stronger DDT criterion. The predicted transition density from this criterion remains below 10(7) g cm(-3) after accounting for intermittency using our intermittency models.Item The Eighth Data Release of the Sloan DIGITal Sky Survey: First Data from SDSS-III(2011-04) Aihara, Hiroaki; Allende Prieto, Carlos; An, Deokkeun; Anderson, Scott F.; Aubourg, Eric; Balbinot, Eduardo; Beers, Timothy C.; Berlind, Andreas A.; Bickerton, Steven J.; Bizyaev, Dmitry; Blanton, Michael R.; Bochanski, John J.; Bolton, Adam S.; Bovy, Jo; Brandt, W. N.; Brinkmann, J.; Brown, Peter J.; Brownstein, Joel R.; Busca, Nicolas G.; Campbell, Heather; Carr, Michael A.; Chen, Yanmei; Chiappini, Cristina; Comparat, Johan; Connolly, Natalia; Cortes, Marina; Croft, Rupert A. C.; Cuesta, Antonio J.; da Costa, Luiz N.; Davenport, James R. A.; Dawson, Kyle; Dhital, Saurav; Ealet, Anne; Ebelke, Garrett L.; Edmondson, Edward M.; Eisenstein, Daniel J.; Escoffier, Stephanie; Esposito, Massimiliano; Evans, Michael L.; Fan, Xiaohui; Femenia Castella, Bruno; Font-Ribera, Andreu; Frinchaboy, Peter M.; Ge, Jian; Gillespie, Bruce A.; Gilmore, G.; Gonzalez Hernandez, Jonay I.; Gott, J. Richard; Gould, Andrew; Grebel, Eva K.; Gunn, James E.; Hamilton, Jean-Christophe; Harding, Paul; Harris, David W.; Hawley, Suzanne L.; Hearty, Frederick R.; Ho, Shirley; Hogg, David W.; Holtzman, Jon A.; Honscheid, Klaus; Inada, Naohisa; Ivans, Inese I.; Jiang, Linhua; Johnson, Jennifer A.; Jordan, Cathy; Jordan, Wendell P.; Kazin, Eyal A.; Kirkby, David; Klaene, Mark A.; Knapp, G. R.; Kneib, Jean-Paul; Kochanek, C. S.; Koesterke, Lars; Kollmeier, Juna A.; Kron, Richard G.; Lampeitl, Hubert; Lang, Dustin; Le Goff, Jean-Marc; Lee, Young Sun; Lin, Yen-Ting; Long, Daniel C.; Loomis, Craig P.; Lucatello, Sara; Lundgren, Britt; Lupton, Robert H.; Ma, Zhibo; MacDonald, Nicholas; Mahadevan, Suvrath; Maia, Marcio A. G.; Makler, Martin; Malanushenko, Elena; Malanushenko, Viktor; Mandelbaum, Rachel; Maraston, Claudia; Margala, Daniel; Masters, Karen L.; McBride, Cameron K.; McGehee, Peregrine M.; McGreer, Ian D.; Menard, Brice; Miralda-Escude, Jordi; Morrison, Heather L.; Mullally, F.; Muna, Demitri; Munn, Jeffrey A.; Murayama, Hitoshi; Myers, Adam D.; Naugle, Tracy; Neto, Angelo Fausti; Duy Cuong, Nguyen; Nichol, Robert C.; O'Connell, Robert W.; Ogando, Ricardo L. C.; Olmstead, Matthew D.; Oravetz, Daniel J.; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Pandey, Parul; Paris, Isabelle; Percival, Will J.; Petitjean, Patrick; Pfaffenberger, Robert; Pforr, Janine; Phleps, Stefanie; Pichon, Christophe; Pieri, Matthew M.; Prada, Francisco; Price-Whelan, Adrian M.; Raddick, M. Jordan; Ramos, Beatriz H. F.; Reyle, Celine; Rich, James; Richards, Gordon T.; Rix, Hans-Walter; Robin, Annie C.; Rocha-Pinto, Helio J.; Rockosi, Constance M.; Roe, Natalie A.; Rollinde, Emmanuel; Ross, Ashley J.; Ross, Nicholas P.; Rossetto, Bruno M.; Sanchez, Ariel G.; Sayres, Conor; Schlegel, David J.; Schlesinger, Katharine J.; Schmidt, Sarah J.; Schneider, Donald P.; Sheldon, Erin; Shu, Yiping; Simmerer, Jennifer; Simmons, Audrey E.; Sivarani, Thirupathi; Snedden, Stephanie A.; Sobeck, Jennifer S.; Steinmetz, Matthias; Strauss, Michael A.; Szalay, Alexander S.; Tanaka, Masayuki; Thakar, Aniruddha R.; Thomas, Daniel; Tinker, Jeremy L.; Tofflemire, Benjamin M.; Tojeiro, Rita; Tremonti, Christy A.; Vandenberg, Jan; Magana, M. Vargas; Verde, Licia; Vogt, Nicole P.; Wake, David A.; Wang, Ji; Weaver, Benjamin A.; Weinberg, David H.; White, Martin; White, Simon D. M.; Yanny, Brian; Yasuda, Naoki; Yeche, Christophe; Zehavi, Idit; Koesterke, LarsThe Sloan Digital Sky Survey (SDSS) started a new phase in 2008 August, with new instrumentation and new surveys focused on Galactic structure and chemical evolution, measurements of the baryon oscillation feature in the clustering of galaxies and the quasar Ly alpha forest, and a radial velocity search for planets around similar to 8000 stars. This paper describes the first data release of SDSS-III (and the eighth counting from the beginning of the SDSS). The release includes five-band imaging of roughly 5200 deg(2) in the southern Galactic cap, bringing the total footprint of the SDSS imaging to 14,555 deg(2), or over a third of the Celestial Sphere. All the imaging data have been reprocessed with an improved sky-subtraction algorithm and a final, self-consistent photometric recalibration and flat-field determination. This release also includes all data from the second phase of the Sloan Extension for Galactic Understanding and Exploration (SEGUE-2), consisting of spectroscopy of approximately 118,000 stars at both high and low Galactic latitudes. All the more than half a million stellar spectra obtained with the SDSS spectrograph have been reprocessed through an improved stellar parameter pipeline, which has better determination of metallicity for high-metallicity stars.Item The Exceptionally Luminous Type Ia Supernova 2007If(2010-06) Yuan, F.; Quimby, Robert M.; Wheeler, J. Craig; Vinko, Jozsef; Chatzopoulos, Emmanouil; Akerlof, C. W.; Kulkarni, S.; Miller, J. M.; McKay, T. A.; Aharonian, F.; Wheeler, J. Craig; Vinko, Jozsef; Chatzopoulos, EmmanouilSN 2007if was the third over-luminous Type Ia supernova (SN Ia) detected after 2003fg and 2006gz. We present the photometric and spectroscopic observations of the SN and its host by ROTSE-III, HET, and Keck. From the H a line identified in the host spectra, we determine a redshift of 0.0736. At this distance, the SN reached an absolute magnitude of -20.4, brighter than any other SNe Ia ever observed. If the source of luminosity is radioactive decay, a large amount of radioactive nickel (similar to 1.5 M(circle dot)) is required to power the peak luminosity, more than can be produced realistically in a Chandrasekhar mass progenitor. Low expansion velocity, similar to that of 2003fg, is also measured around the maximum light. The observations may suggest that SN 2007if was from a massive white dwarf progenitor, plausibly exploding with mass well beyond 1.4 M(circle dot). Alternatively, we investigate circumstellar interaction that may contribute to the excess luminosity.Item The Fast And Furious Decay Of The Peculiar Type Ic Supernova 2005Ek(2013-09) Drout, M. R.; Soderberg, Alicia M.; Mazzali, P. A.; Parrent, Jerod T.; Margutti, R.; Milisavljevic, Dan; Sanders, N. E.; Chornock, Ryan; Foley, Ryan J.; Kirshner, Robert P.; Filippenko, Alexei V.; Li, W.; Brown, Peter J.; Cenko, S. Bradley; Chakraborti, S.; Challis, Peter; Friedman, A.; Ganeshalingam, Mohan; Hicken, M.; Jensen, C.; Modjaz, M.; Perets, H. B.; Silverman, Jeffrey M.; Wong, D. S.; Silverman, Jeffrey M.We present extensive multi-wavelength observations of the extremely rapidly declining Type Ic supernova (SN Ic), SN 2005ek. Reaching a peak magnitude of MR = -17.3 and decaying by similar to 3 mag in the first 15 days post-maximum, SN 2005ek is among the fastest Type I supernovae observed to date. The spectra of SN 2005ek closely resemble those of normal SN Ic, but with an accelerated evolution. There is evidence for the onset of nebular features at only nine days post-maximum. Spectroscopic modeling reveals an ejecta mass of similar to 0.3 M-circle dot that is dominated by oxygen (similar to 80%), while the pseudo-bolometric light curve is consistent with an explosion powered by similar to 0.03 M-circle dot of radioactive Ni-56. Although previous rapidly evolving events (e. g., SN 1885A, SN 1939B, SN 2002bj, SN 2010X) were hypothesized to be produced by the detonation of a helium shell on a white dwarf, oxygen-dominated ejecta are difficult to reconcile with this proposed mechanism. We find that the properties of SN 2005ek are consistent with either the edge-lit double detonation of a low-mass white dwarf or the iron-core collapse of a massive star, stripped by binary interaction. However, if we assume that the strong spectroscopic similarity of SN 2005ek to other SNe Ic is an indication of a similar progenitor channel, then a white-dwarf progenitor becomes very improbable. SN 2005ek may be one of the lowest mass stripped-envelope core-collapse explosions ever observed. We find that the rate of such rapidly declining Type I events is at least 1%-3% of the normal SN Ia rate.Item The First Two Transient Supersoft X-Ray Sources In M 31 Globular Clusters And The Connection To Classical Novae(2009-06) Henze, M.; Pietsch, W.; Haberl, F.; Sala, G.; Quimby, R.; Hernanz, M.; Della Valle, M.; Milne, P.; Williams, G. G.; Burwitz, V.; Greiner, J.; Stiele, H.; Hartmann, D. H.; Kong, A. K. H.; Hornoch, K.; Quimby, R.Context. Classical novae (CNe) have been found to represent the major class of supersoft X-ray sources (SSSs) in our neighbour galaxy M 31. Aims. We determine the properties and evolution of the two first SSSs ever discovered in the M 31 globular cluster (GC) system. Methods. We have used XMM-Newton, Chandra and Swift observations of the centre region of M 31 to discover both SSSs and to determine their X-ray light curves and spectra. We performed detailed analysis of XMM-Newton EPIC PN spectra of the source in Bol 111 (SS1) using blackbody and NLTE white dwarf (WD) atmosphere models. For the SSS in Bol 194 (SS2) we used optical monitoring data to search for an optical counterpart. Results. Both GC X-ray sources were classified as SSS. We identify SS1 with the CN M31N 2007-06b recently discovered in the M 31 GC Bol 111. For SS2 we did not find evidence for a recent nova outburst and can only provide useful constraints on the time of the outburst of a hypothetical nova. Conclusions. The only known CN in a M 31 GC can be identified with the first SSS found in a M 31 GC. We discuss the impact of our observations on the nova rate for the M 31 GC system.Item Galactic Globular and Open Clusters in the Sloan DIGITal Sky Survey. I. Crowded-Field Photometry and Cluster Fiducial Sequences in Ugriz(2008-12) An, Deokkeun; Johnson, Jennifer A.; Clem, James L.; Yanny, Brian; Rockosi, Constance M.; Morrison, Heather L.; Harding, Paul; Gunn, James E.; Prieto, Carlos Allende; Beers, Timothy C.; Cudworth, Kyle M.; Ivans, Inese I.; Ivezic, Zeljko; Lee, Young Sun; Lupton, Robert H.; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Dan; Pan, Kaike; Simmons, Audrey; Snedden, Stephanie; Watters, Shannon; York, Donald G.; Prieto, Carlos AllendWe present photometry for globular and open cluster stars observed with the Sloan Digital Sky Survey (SDSS). In order to exploit the over 100 million stellar objects with r < 22:5 mag observed by SDSS, we need to understand the characteristics of stars in the SDSS ugriz filters. While star clusters provide important calibration samples for stellar colors, the regions close to globular clusters, where the fraction of field stars is smallest, are too crowded for the standard SDSS photometric pipeline to process. To complement the SDSS imaging survey, we reduce the SDSS imaging data for crowded cluster fields using the DAOPHOT/ALLFRAME suite of programs and present photometry for 17 globular clusters and three open clusters in a SDSS value-added catalog. Our photometry and cluster fiducial sequences are on the native SDSS 2.5 m ugriz photometric system, and the fiducial sequences can be directly applied to the SDSS photometry without relying on any transFormations. Model photometry for red giant branch and main-sequence stars obtained by Girardi et al. cannot be matched simultaneously to fiducial sequences; their colors differ by similar to 0.02-0.05 mag. Good agreement (similar to 0.02 mag in colors) is found with Clem et al. empirical fiducial sequences in u'g'r'i'z' when using the transFormation equations in Tucker et al.Item Hubble Space Telescope Fine Guidance Sensor Parallaxes For Four Classical Novae(2013-04) Harrison, Thomas E.; Bornak, Jilian; McArthur, Barbara E.; Benedict, G. Fritz; McArthur, Barbara E.; Benedict, G. FritzWe have used data obtained with the Fine Guidance Sensors on the Hubble Space Telescope to derive precise astrometric parallaxes for four classical novae: V603 Aql, DQ Her, GK Per, and RR Pic. All four objects exceeded the Eddington limit at visual maximum. Re-examination of the original light curve data for V603 Aql and GK Per has led us to conclude that their visual maxima were slightly brighter than commonly assumed. With known distances, we examine the various maximum magnitude-rate of decline relationships that have been established for classical novae. We find that these four objects show a similar level of scatter about these relationships as seen in larger samples of novae whose distances were determined using indirect techniques. We also examine the nebular expansion parallax method and find that it fails for three of the four objects. In each case it was possible to find an explanation for the failure of that technique to give precise distance estimates. DQ Her appears to suffer from an anomalously high extinction when compared to field stars on its sight line. We suggest that this is likely due to local material, which may also be the source of the IRAS detections of this object.Item Identification Of Faint Chandra X-Ray Sources In The Core-Collapsed Globular Cluster NGC 6397: Evidence For A Bimodal Cataclysmic Variable Population(2010-10) Cohn, Haldan N.; Lugger, Phyllis M.; Couch, Sean M.; Anderson, Jay; Cool, Adrienne M.; van den Berg, Maureen; Bogdanov, Slavko; Heinke, Craig O.; Grindlay, Jonathan E.; Couch, Sean M.We have searched for optical identifications for 79 Chandra X-ray sources that lie within the half-mass radius of the nearby, core-collapsed globular cluster NGC 6397, using deep Hubble Space Telescope Advanced Camera for Surveys Wide Field Channel imaging in H alpha, R, and B. Photometry of these images allows us to classify candidate counterparts based on color-magnitude diagram location. In addition to recovering nine previously detected cataclysmic variables (CVs), we have identified six additional faint CV candidates, a total of 42 active binaries (ABs), two millisecond pulsars, one candidate active galactic nucleus, and one candidate interacting galaxy pair. Of the 79 sources, 69 have a plausible optical counterpart. The 15 likely and possible CVs in NGC 6397 mostly fall into two groups: a brighter group of six for which the optical emission is dominated by contributions from the secondary and accretion disk and a fainter group of seven for which the white dwarf dominates the optical emission. There are two possible transitional objects that lie between these groups. The faintest CVs likely lie near the minimum of the CV period distribution, where an accumulation is expected. The spatial distribution of the brighter CVs is much more centrally concentrated than those of the fainter CVs and the ABs. This may represent the result of an evolutionary process in which CVs are produced by dynamical interactions, such as exchange reactions, near the cluster center and are scattered to larger orbital radii, over their lifetimes, as they age and become fainter.Item Linking Type Ia Supernova Progenitors And Their Resulting Explosions(2012-06) Foley, Ryan J.; Simon, Joshua D.; Burns, Christopher R.; Gal-Yam, Avishay; Hamuy, Mario; Kirshner, Robert P.; Morrell, Nidia I.; Phillips, Mark M.; Shields, Gregory A.; Sternberg, Assaf; Shields, Gregory A.Comparing the ejecta velocities at maximum brightness and narrow circumstellar/interstellar Na D absorption line profiles of a sample of 23 Type Ia supernovae (SNe Ia), we determine that the properties of SN Ia progenitor systems and explosions are intimately connected. As demonstrated by Sternberg et al., half of all SNe Ia with detectable Na D absorption at the host-galaxy redshift in high-resolution spectroscopy have Na D line profiles with significant blueshifted absorption relative to the strongest absorption component, which indicates that a large fraction of SN Ia progenitor systems have strong outflows. In this study, we find that SNe Ia with blueshifted circumstellar/interstellar absorption systematically have higher ejecta velocities and redder colors at maximum brightness relative to the rest of the SN Ia population. This result is robust at a 98.9%-99.8% confidence level, providing the first link between the progenitor systems and properties of the explosion. This finding is further evidence that the outflow scenario is the correct interpretation of the blueshifted Na D absorption, adding additional confirmation that some SNe Ia are produced from a single-degenerate progenitor channel. An additional implication is that either SN Ia progenitor systems have highly asymmetric outflows that are also aligned with the SN explosion or SNe Ia come from a variety of progenitor systems where SNe Ia from systems with strong outflows tend to have more kinetic energy per unit mass than those from systems with weak or no outflows.Item Modules for Experiments in Stellar Astrophysics (MESA): Planets, Oscillations, Rotation, and Massive Stars(2013-09) Paxton, Bill; Cantiello, Matteo; Arras, Phil; Bildsten, Lars; Brown, Edward F.; Dotter, Aaron; Mankovich, Christopher; Montgomery, M. H.; Stello, Dennis; Timmes, F. X.; Townsend, Richard; Montgomery, M. H.We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESAstar. Improvements in MESAstar's ability to model the evolution of giant planets now extends its applicability down to masses as low as one-tenth that of Jupiter. The dramatic improvement in asteroseismology enabled by the space-based Kepler and CoRoT missions motivates our full coupling of the ADIPLS adiabatic pulsation code with MESAstar. This also motivates a numerical recasting of the Ledoux criterion that is more easily implemented when many nuclei are present at non-negligible abundances. This impacts the way in which MESAstar calculates semi-convective and thermohaline mixing. We exhibit the evolution of 3-8 M-circle dot stars through the end of core He burning, the onset of He thermal pulses, and arrival on the white dwarf cooling sequence. We implement diffusion of angular momentum and chemical abundances that enable calculations of rotating-star models, which we compare thoroughly with earlier work. We introduce a new treatment of radiation-dominated envelopes that allows the uninterrupted evolution of massive stars to core collapse. This enables the generation of new sets of supernovae, long gamma-ray burst, and pair-instability progenitor models. We substantially modify the way in which MESAstar solves the fully coupled stellar structure and composition equations, and we show how this has improved the scaling of MESA's calculational speed on multi-core processors. Updates to the modules for equation of state, opacity, nuclear reaction rates, and atmospheric boundary conditions are also provided. We describe the MESA Software Development Kit that packages all the required components needed to form a unified, maintained, and well-validated build environment for MESA. We also highlight a few tools developed by the community for rapid visualization of MESAstar results.Item The Near-Ultraviolet Luminosity Function Of Young, Early M-Type Dwarf Stars(2015-01) Ansdell, Megan; Gaidos, Eric; Mann, Andrew W.; Lepine, Sebastien; James, David; Buccino, Andrea; Baranec, Christoph; Law, Nicolas M.; Riddle, Reed; Mauas, Pablo; Petrucci, Romina; Mann, Andrew W.Planets orbiting within the close-in habitable zones of M dwarf stars will be exposed to elevated high-energy radiation driven by strong magnetohydrodynamic dynamos during stellar youth. Near-ultraviolet (NUV) irradiation can erode and alter the chemistry of planetary atmospheres, and a quantitative description of the evolution of NUV emission from M dwarfs is needed when modeling these effects. We investigated the NUV luminosity evolution of early M-type dwarfs by cross-correlating the Lepine & Gaidos catalog of bright M dwarfs with the Galaxy Evolution Explorer (GALEX) catalog of NUV (1771-2831 angstrom) sources. Of the 4805 sources with GALEX counterparts, 797 have NUV emission significantly (>2.5 sigma) in excess of an empirical basal level. We inspected these candidate active stars using visible-wavelength spectra, high-resolution adaptive optics imaging, time-series photometry, and literature searches to identify cases where the elevated NUV emission is due to unresolved background sources or stellar companions; we estimated the overall occurrence of these "false positives" (FPs) as similar to 16%. We constructed an NUV luminosity function that accounted for FPs, detection biases of the source catalogs, and GALEX upper limits. We found the NUV luminosity function to be inconsistent with predictions from a constant star-formation rate and simplified age-activity relation defined by a two-parameter power law.Item Oxygen Isotopic Ratios In Cool R Coronae Borealis Stars(2010-05) Garcia-Hernandez, D. Anibal; Lambert, David L.; Rao, N. Kameswara; Hinkle, Ken. H.; Eriksson, Kiell; Lambert, David L.We investigate the relationship between R Coronae Borealis (RCB) stars and hydrogen-deficient carbon (HdC) stars by measuring precise (16)O/(18)O ratios for five cool RCB stars. The (16)O/(18)O ratios are derived by spectrum synthesis from high-resolution (R similar to 50,000) K-band spectra. Lower limits to the (16)O/(17)O and (14)N/(15)N ratios as well as Na and S abundances (when possible) are also given. RCB stars in our sample generally display less (18)O than HdC stars-the derived (16)O/(18)O ratios range from 3 to 20. The only exception is the RCB star WX CrA, which seems to be an HdC-like star with (16)O/(18)O = 0.3. Our result of a higher (16)O/(18)O ratio for the RCB stars must be accounted for by a theory of the formation and evolution of HdC and RCB stars. We speculate that a late dredge-up of products of He burning, principally (12)C and (16)O, may convert an (18)O-rich HdC star into an (18)O-poor RCB star as the H-deficient star begins its final evolution from a cool supergiant to the top of the white dwarf cooling track.Item The Sixth Data Release of the Sloan DIGITal Sky Survey(2008-04) Adelman-McCarthy, Jennifer K.; Agueros, Marcel A.; Allam, Sahar S.; Prieto, Carlos Allende; Anderson, Kurt S. J.; Anderson, Scott F.; Annis, James; Bahcall, Neta A.; Bailer-Jones, C. A. L.; Baldry, Ivan K.; Barentine, J. C.; Bassett, Bruce A.; Becker, Andrew C.; Beers, Timothy C.; Bell, Eric F.; Berlind, Andreas A.; Bernardi, Mariangela; Blanton, Michael R.; Bochanski, John J.; Boroski, William N.; Brinchmann, Jarle; Brinkmann, J.; Brunner, Robert J.; Budavari, Tamas; Carliles, Samuel; Carr, Michael A.; Castander, Francisco J.; Cinabro, David; Cool, R. J.; Covey, Kevin R.; Csabai, Istvan; Cunha, Carlos E.; Davenport, James R. A.; Dilday, Ben; Doi, Mamoru; Eisenstein, Daniel J.; Evans, Michael L.; Fan, Xiaohui; Finkbeiner, Douglas P.; Friedman, Scott D.; Frieman, Joshua A.; Fukugita, Masataka; Gansicke, Boris T.; Gates, Evalyn; Gillespie, Bruce; Glazebrook, Karl; Gray, Jim; Grebel, Eva K.; Gunn, James E.; Gurbani, Vijay K.; Hall, Patrick B.; Harding, Paul; Harvanek, Michael; Hawley, Suzanne L.; Hayes, Jeffrey; Heckman, Timothy M.; Hendry, John S.; Hindsley, Robert B.; Hirata, Christopher M.; Hogan, Craig J.; Hogg, David W.; Hyde, Joseph B.; Ichikawa, Shin-ichi; Ivezic, Zeljko; Jester, Sebastian; Johnson, Jennifer A.; Jorgensen, Anders M.; Juric, Mario; Kent, Stephen M.; Kessler, R.; Kleinman, S. J.; Knapp, G. R.; Kron, Richard G.; Krzesinski, Jurek; Kuropatkin, Nikolay; Lamb, Donald Q.; Lampeitl, Hubert; Lebedeva, Svetlana; Lee, Young Sun; Leger, R. French; Lepine, Sebastien; Lima, Marcos; Lin, Huan; Long, Daniel C.; Loomis, Craig P.; Loveday, Jon; Lupton, Robert H.; Malanushenko, Olena; Malanushenko, Viktor; Mandelbaum, Rachel; Margon, Bruce; Marriner, John P.; Martinez-Delgado, David; Matsubara, Takahiko; McGehee, Peregrine M.; McKay, Timothy A.; Meiksin, Avery; Morrison, Heather L.; Munn, Jeffrey A.; Nakajima, Reiko; Neilsen, Eric H., Jr.; Newberg, Heidi Jo; Nichol, Robert C.; Nicinski, Tom; Nieto-Santisteban, Maria; Nitta, Atsuko; Okamura, Sadanori; Owen, Russell; Oyaizu, Hiroaki; Padmanabhan, Nikhil; Pan, Kaike; Park, Changbom; Peoples, John, Jr.; Pier, Jeffrey R.; Pope, Adrian C.; Purger, Norbert; Raddick, M. Jordan; Fiorentin, Paola Re; Richards, Gordon T.; Richmond, Michael W.; Riess, Adam G.; Rix, Hans-Walter; Rockosi, Constance M.; Sako, Masao; Schlegel, David J.; Schneider, Donald P.; Schreiber, Matthias R.; Schwope, Axel D.; Seljak, Uros; Sesar, Branimir; Sheldon, Erin; Shimasaku, Kazu; Sivarani, Thirupathi; Smith, J. Allyn; Snedden, Stephanie A.; Steinmetz, Matthias; Strauss, Michael A.; SubbaRao, Mark; Suto, Yasushi; Szalay, Alexander S.; Szapudi, Istvan; Szkody, Paula; Tegmark, Max; Thakar, Aniruddha R.; Tremonti, Christy A.; Tucker, Douglas L.; Uomoto, Alan; Berk, Daniel E. Vanden; Vandenberg, Jan; Vidrih, S.; Vogeley, Michael S.; Voges, Wolfgang; Vogt, Nicole P.; Wadadekar, Yogesh; Weinberg, David H.; West, Andrew A.; White, Simon D. M.; Wilhite, Brian C.; Yanny, Brian; Yocum, D. R.; York, Donald G.; Zehavi, Idit; Zucker, Daniel B.; Prieto, Carlos Allende; Barentine, J. C.This paper describes the Sixth Data Release of the Sloan Digital Sky Survey. With this data release, the imaging of the northern Galactic cap is now complete. The survey contains images and parameters of roughly 287 million objects over 9583 deg(2), including scans over a large range of Galactic latitudes and longitudes. The survey also includes 1.27 million spectra of stars, galaxies, quasars, and blank sky ( for sky subtraction) selected over 7425 deg2. This release includes much more stellar spectroscopy than was available in previous data releases and also includes detailed estimates of stellar temperatures, gravities, and metallicities. The results of improved photometric calibration are now available, with uncertainties of roughly 1% in g, r, i, and z, and 2% in u, substantially better than the uncertainties in previous data releases. The spectra in this data release have improved wavelength and flux calibration, especially in the extreme blue and extreme red, leading to the qualitatively better determination of stellar types and radial velocities. The spectrophotometric fluxes are now tied to point-spread function magnitudes of stars rather than fiber magnitudes. This gives more robust results in the presence of seeing variations, but also implies a change in the spectrophotometric scale, which is now brighter by roughly 0.35 mag. Systematic errors in the velocity dispersions of galaxies have been fixed, and the results of two independent codes for determining spectral classifications and red-shifts are made available. Additional spectral outputs are made available, including calibrated spectra from individual 15 minute exposures and the sky spectrum subtracted from each exposure. We also quantify a recently recognized underestimation of the brightnesses of galaxies of large angular extent due to poor sky subtraction; the bias can exceed 0.2 mag for galaxies brighter than r = 14 mag.Item Spectroscopic Observations Of Sn 2012fr: A Luminous, Normal Type Ia Supernova With Early High-Velocity Features And A Late Velocity Plateau(2013-06) Childress, M. J.; Scalzo, R. A.; Sim, S. A.; Tucker, B. E.; Yuan, F.; Schmidt, Brian P.; Cenko, S. Bradley; Silverman, Jeffrey M.; Contreras, C.; Hsiao, Eric Y.; Phillips, M.; Morrell, N.; Jha, Saurabh W.; McCully, C.; Filippenko, Alexei V.; Anderson, J. P.; Benetti, S.; Bufano, F.; de Jaeger, T.; Forster, F.; Gal-Yam, Avishay; Le Guillou, L.; Maguire, K.; Maund, J.; Mazzali, P. A.; Pignata, G.; Smartt, S.; Spyromilio, J.; Sullivan, Mark; Taddia, F.; Valenti, S.; Bayliss, D. D. R.; Bessell, M.; Blanc, Guillermo A.; Carson, D. J.; Clubb, K. I.; de Burgh-Day, C.; Desjardins, T. D.; Fang, J. J.; Fox, O. D.; Gates, E. L.; Ho, I. T.; Keller, S.; Kelly, P. L.; Lidman, C.; Loaring, N. S.; Mould, J. R.; Owers, M.; Ozbilgen, S.; Pei, L.; Pickering, T.; Pracy, M. B.; Rich, J. A.; Schaefer, B. E.; Scott, N.; Stritzinger, Maximillian; Vogt, F. P. A.; Zhou, G.; Silverman, Jeffrey M.We present 65 optical spectra of the Type Ia SN 2012fr, 33 of which were obtained before maximum light. At early times, SN 2012fr shows clear evidence of a high-velocity feature (HVF) in the Si lambda 6355 line that can be cleanly decoupled from the lower velocity "photospheric" component. This Si lambda 6355 HVF fades by phase - 5; subsequently, the photospheric component exhibits a very narrow velocity width and remains at a nearly constant velocity of similar to 12,000 km s(-1) until at least five weeks after maximum brightness. The Ca II infrared triplet exhibits similar evidence for both a photospheric component at v approximate to 12,000 km s(-1) with narrow line width and long velocity plateau, as well as an HVF beginning at v approximate to 31,000 km s(-1) two weeks before maximum. SN 2012fr resides on the border between the "shallow silicon" and "core-normal" subclasses in the Branch et al. classification scheme, and on the border between normal and high-velocity Type Ia supernovae (SNe Ia) in the Wang et al. system. Though it is a clear member of the "low velocity gradient" group of SNe Ia and exhibits a very slow light-curve decline, it shows key dissimilarities with the overluminous SN 1991T or SN 1999aa subclasses of SNe Ia. SN 2012fr represents a well-observed SN Ia at the luminous end of the normal SN Ia distribution and a key transitional event between nominal spectroscopic subclasses of SNe Ia.Item VLT Spectropolarimetry Of The Type Ia SN 2005ke A Step Towards Understanding Subluminous Events(2012-09) Patat, F.; Hoflich, P.; Baade, D.; Maund, J. R.; Wang, L.; Wheeler, J. C.; Wheeler, J. C.Aims. In this study we try to answer the question whether or not subluminous Type Ia supernovae have additional distinctive properties when examined from the point of view of the explosion geometry. Methods. We have performed optical spectropolarimetric observations of the Type Ia SN 2005ke at 3 epochs (days -8, -7, and +76). The explosion properties are derived by comparing the data to explosion and radiation transfer models. Results. The supernova shows polarimetric properties that are very similar to the only other subluminous event for which spectropolarimetry is available, i.e. SN 1999by. The data present a very marked dominant axis, which is shared by both the continuum and lines such as Si II lambda 6355, suggesting that the relatively large, global asymmetry is common to the photosphere and the line-forming region. The maximum polarization degree observed in the Si II lambda 6355 absorption reaches 0.39 +/- 0.08%. At variance with what is seen in core-normal Type Ia, SN 2005ke displays significant continuum polarization, which grows from the blue to the red and peaks at about 7000 angstrom, reaching similar to 0.7%. The properties of the polarization and flux spectra can be understood within the framework of a subluminous delayed-detonation (DD), or pulsating DD scenario, or white dwarf (WD) mergers. The difference in appearance with respect to core-normal SNe Ia is caused by low photospheric temperatures in combination with layers of unburned C, and more massive layers of the products of explosive C and O burning. The comparatively high level of continuum polarization is explained in terms of a significant global asymmetry (similar to 15%), which is well reproduced by an oblate ellipsoidal geometry within the general context of a DD explosion. Conclusions. Our results suggest that SN 2005ke arose either from a single-degenerate system in which the WD is especially rapidly rotating, close to the break-up velocity, or from a double-degenerate merger. Based on the current polarization data, we cannot distinguish between these two possibilities. Possible tests are discussed.