Browsing by Subject "data release"

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The Apache Point Observatory Galactic Evolution Experiment: First Detection of High-Velocity Milky Way Bar Stars
(2012-08) Nidever, David L.; Zasowski, Gail; Majewski, Steven R.; Bird, Jonathan; Robin, Annie C.; Martinez-Valpuesta, Inma; Beaton, Rachael L.; Schoenrich, Ralph; Schultheis, Mathias; Wilson, John C.; Skrutskie, Michael F.; O'Connell, Robert W.; Shetrone, Matthew; Schiavon, Ricardo P.; Johnson, Jennifer A.; Weiner, Benjamin; Gerhard, Ortwin; Schneider, Donald P.; Prieto, Carlos Allende; Sellgren, Kris; Bizyaev, Dmitry; Brewington, Howard; Brinkmann, Jon; Eisenstein, Daniel J.; Frinchaboy, Peter M.; Perez, Ana Elia Garcia; Holtzman, Jon; Hearty, Fred R.; Malanushenko, Elena; Malanushenko, Viktor; Muna, Demitri; Oravetz, Daniel; Pan, Kaike; Simmons, Audrey; Snedden, Stephanie; Weaver, Benjamin A.; Shetrone, Matthew
Commissioning observations with the Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III, have produced radial velocities (RVs) for similar to 4700 K/M-giant stars in the Milky Way (MW) bulge. These high-resolution (R similar to 22,500), high-S/N (>100 per resolution element), near-infrared (NIR; 1.51-1.70 mu m) spectra provide accurate RVs (epsilon(V) similar to 0.2 km s(-1)) for the sample of stars in 18 Galactic bulge fields spanning -1 degrees < l < 20 degrees, vertical bar b vertical bar < 20 degrees, and delta > -32 degrees. This represents the largest NIR high-resolution spectroscopic sample of giant stars ever assembled in this region of the Galaxy. A cold (sigma(V) similar to 30 km s(-1)), high-velocity peak (V-GSR approximate to + 200 km s(-1)) is found to comprise a significant fraction (similar to 10%) of stars in many of these fields. These high RVs have not been detected in previous MW surveys and are not expected for a simple, circularly rotating disk. Preliminary distance estimates rule out an origin from the background Sagittarius tidal stream or a new stream in the MW disk. Comparison to various Galactic models suggests that these high RVs are best explained by stars in orbits of the Galactic bar potential, although some observational features remain unexplained.
The Black Hole Mass-Galaxy Luminosity Relationship For Sloan Digital Sky Survey Quasars
(2015-02) Salviander, Sarah; Shields, Gregory A.; Bonning, E. W.; Salviander, Sarah; Shields, Gregory A.
We investigate the relationship between the mass of the central supermassive black hole, M-BH, and the host galaxy luminosity, L-gal, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M-BH-L-gal relationship by examining the redshift dependence of Delta log M-BH, the offset in M-BH from the local M-BH-L-gal relationship. There is little systematic trend in. log MBH out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, sigma(*), we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for sigma(*) in statistical studies.
The Century Survey Galactic Halo Project. III. A Complete 4300 Deg(2) Survey Of Blue Horizontal Branch Stars In The Metal-Weak Thick Disk And Inner Halo
(2008-02) Brown, Warren R.; Beers, Timothy C.; Wilhelm, Ronald; Prieto, Carlos Allende; Geller, Margaret J.; Kenyon, Scott J.; Kurtz, Michael J.; Prieto, Carlos Allende
We present a complete spectroscopic survey of 2414 2MASS-selected blue horizontal branch ( BHB) candidates selected over 4300 deg(2) of the sky. We identify 655 BHB stars in this non-kinematically selected sample. We calculate the luminosity function of field BHB stars, and find evidence for very few hot BHB stars in the field. The BHB stars located at a distance from the Galactic plane | Z| < 4 kpc trace what is clearly a metal-weak thick disk population, with a mean metallicity of [Fe/H]=-1.7, a rotation velocity gradient of dv(rot)/d|Z|=-28 +/- 3.4 km s(-1) in the region |Z| < 6 kpc, and a density scale height of h(Z) = 1.26 +/- 0.1 kpc. The BHB stars located at 5 < | Z| < 9 kpc are a predominantly inner-halo population, with a mean metallicity of [ Fe/ H] = - 2.0 and a mean Galactic rotation of - 4 +/- 31 km s(-1). We infer the density of halo and thick disk BHB stars is 104 +/- 37 kpc(-3) near the Sun, and the relative normalization of halo to thick-disk BHB stars is 4 +/- 1% near the Sun.
Chemical Cartography With Apogee: Large-Scale Mean Metallicity Maps Of The Milky Way Disk
(2014-05) Michael R. Hayden; Jon A. Holtzman; Jo Bovy; Steven R. Majewski; Jennifer A. Johnson; Carlos Allende Prieto; Timothy C. Beers; Katia Cunha; Peter M. Frinchaboy; Ana E. García Pérez; Léo Girardi; Fred R. Hearty; Young Sun Lee; David Nidever; Ricardo P. Schiavon; Katharine J. Schlesinger; Donald P. Schneider; Mathias Schultheis; Matthew Shetrone; Verne V. Smith; Gail Zasowski; Dmitry Bizyaev; Diane Feuillet; Sten Hasselquist; Karen Kinemuchi; Elena Malanushenko; Viktor Malanushenko; Robert O'Connell; Kaike Pan; Keivan Stassun; Shetrone, Matthew D.
We present Galactic mean metallicity maps derived from the first year of the SDSS-III APOGEE experiment. Mean abundances in different zones of projected Galactocentric radius (0 < R < 15 kpc) at a range of heights above the plane (0 < vertical bar z vertical bar < 3 kpc), are derived from a sample of nearly 20,000 giant stars with unprecedented coverage, including stars in the Galactic mid-plane at large distances. We also split the sample into subsamples of stars with low- and high-[alpha/M] abundance ratios. We assess possible biases in deriving the mean abundances, and find that they are likely to be small except in the inner regions of the Galaxy. A negative radial metallicity gradient exists over much of the Galaxy; however, the gradient appears to flatten for R < 6 kpc, in particular near the Galactic mid-plane and for low-[alpha/M] stars. At R > 6 kpc, the gradient flattens as one moves off the plane, and is flatter at all heights for high-[alpha/M] stars than for low-[alpha/M] stars. Alternatively, these gradients can be described as vertical gradients that flatten at larger Galactocentric radius; these vertical gradients are similar for both low- and high-[alpha/M] populations. Stars with higher [alpha/M] appear to have a flatter radial gradient than stars with lower [alpha/M]. This could suggest that the metallicity gradient has grown steeper with time or, alternatively, that gradients are washed out over time by migration of stars.
A Detailed Model Atmosphere Analysis of Cool White Dwarfs in the Sloan DIGITal Sky Survey
(2010-09) Kilic, Mukremin; Leggett, S. K.; Tremblay, P. E.; von Hippel, Ted; Bergeron, P.; Harris, Hugh C.; Munn, Jeffrey A.; Williams, Kurtis A.; Gates, Evalyn; Farihi, J.; Williams, Kurtis A.
We present optical spectroscopy and near-infrared photometry of 126 cool white dwarfs (WDs) in the Sloan Digital Sky Survey (SDSS). Our sample includes high proper motion targets selected using the SDSS and USNOB astrometry and a dozen previously known ultracool WD candidates. Our optical spectroscopic observations demonstrate that a clean selection of large samples of cool WDs in the SDSS (and the SkyMapper, Pan-STARRS, and the Large Synoptic Survey Telescope data sets) is possible using a reduced proper motion diagram and a tangential velocity cut-off (depending on the proper motion accuracy) of 30 km s(-1). Our near-infrared observations reveal eight new stars with significant absorption. We use the optical and near-infrared photometry to perform a detailed model atmosphere analysis. More than 80% of the stars in our sample are consistent with either pure hydrogen or pure helium atmospheres. However, the eight stars with significant infrared absorption and the majority of the previously known ultracool WD candidates are best explained with mixed hydrogen and helium atmosphere models. The age distribution of our sample is consistent with a Galactic disk age of 8 Gyr. A few ultracool WDs may be as old as 12-13 Gyr, but our models have problems matching the spectral energy distributions of these objects. There are only two halo WD candidates in our sample. However, trigonometric parallax observations are required for accurate mass and age determinations and to confirm their membership in the halo.
Distances To Galactic High-Velocity Clouds: Complex C
(2007-12) Wakker, B. P.; York, D. G.; Howk, J. C.; Barentine, John C.; Wilhelm, R.; Peletier, R. F.; van Woerden, H.; Beers, Timothy C.; Ivezic, Z.; Richter, P.; Schwarz, U. J.; Barentine, John C.
We report the first determination of a distance bracket for the high- velocity cloud (HVC) complex C. Combined with previous measurements showing that this cloud has a metallicity of 0.15 times solar, these results provide ample evidence that complex C traces the continuing accretion of intergalactic gas falling onto the Milky Way. Accounting for both neutral and ionized hydrogen as well as He, the distance bracket implies a mass of (3-14) x 10(6) M-circle dot, and the complex represents a mass inflow of 0.1-0.25 M-circle dot yr(-1). We base our distance bracket on the detection of Ca II absorption in the spectrum of the blue horizontal branch (BHB) star SDSS J120404.78 + 623345.6, in combination with a significant nondetection toward the BHB star BS 16034-0114. These results set a strong distance bracket of 3.7-11.2 kpc on the distance to complex C. A more weakly supported lower limit of 6.7 kpc may be derived from the spectrum of the BHB star BS 16079-0017.
Extinction Maps Toward The Milky Way Bulge: Two-Dimensional And Three-Dimensional Tests With APOGEE
(2014-07) Schultheis, M.; Zasowski, G.; Prieto, C. A.; Anders, F.; Beaton, R. L.; Beers, T. C.; Bizyaev, D.; Chiappini, C.; Frinchaboy, P. M.; Perez, A. E. G.; Ge, J.; Hearty, F.; Holtzman, J.; Majewski, S. R.; Muna, D.; Nidever, D.; Shetrone, M.; Schneider, D. P.; Shetrone, Matthew D.
Galactic interstellar extinction maps are powerful and necessary tools for Milky Way structure and stellar population analyses, particularly toward the heavily reddened bulge and in the midplane. However, due to the difficulty of obtaining reliable extinction measures and distances for a large number of stars that are independent of these maps, tests of their accuracy and systematics have been limited. Our goal is to assess a variety of photometric stellar extinction estimates, including both two-dimensional and three-dimensional extinction maps, using independent extinction measures based on a large spectroscopic sample of stars toward the Milky Way bulge. We employ stellar atmospheric parameters derived from high-resolution H-band Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra, combined with theoretical stellar isochrones, to calculate line-of-sight extinction and distances for a sample of more than 2400 giants toward the Milky Way bulge. We compare these extinction values to those predicted by individual near-IR and near+mid-IR stellar colors, two-dimensional bulge extinction maps, and three-dimensional extinction maps. The long baseline, near+mid-IR stellar colors are, on average, the most accurate predictors of the APOGEE extinction estimates, and the two-dimensional and three-dimensional extinction maps derived from different stellar populations along different sightlines show varying degrees of reliability. We present the results of all of the comparisons and discuss reasons for the observed discrepancies. We also demonstrate how the particular stellar atmospheric models adopted can have a strong impact on this type of analysis, and discuss related caveats.
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 Allend
We 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.
The Herschel Stripe 82 Survey (HerS): Maps and Early Catalog
(2014-02) Viero, M. P.; Asboth, V.; Roseboom, I. G.; Moncelsi, L.; Marsden, G.; Cooper, E. Mentuch; Zemcov, M.; Addison, G.; Baker, A. J.; Beelen, A.; Bock, J.; Bridge, C.; Conley, A.; Devlin, M. J.; Dore, O.; Farrah, D.; Finkelstein, S.; Font-Ribera, A.; Geach, J. E.; Gebhardt, Karl; Gill, A.; Glenn, Jason; Hajian, A.; Halpern, M.; Jogee, S.; Kurczynski, P.; Lapi, A.; Negrello, M.; Oliver, S. J.; Papovich, C.; Quadri, R.; Ross, N.; Scott, D.; Schulz, B.; Somerville, R.; Spergel, D. N.; Vieira, J. D.; Wang, L.; Wechsler, R.; Cooper, E. Mentuch; Finkelstein, S.; Jogee, S.
We present the first set of maps and band-merged catalog from the Herschel Stripe 82 Survey (HerS). Observations at 250, 350, and 500 mu m were taken with the Spectral and Photometric Imaging Receiver instrument aboard the Herschel Space Observatory. HerS covers 79 deg(2) along the SDSS Stripe 82 to an average depth of 13.0, 12.9, and 14.8 mJy beam(-1) (including confusion) at 250, 350, and 500 mu m, respectively. HerS was designed to measure correlations with external tracers of the dark matter density field-either point-like (i.e., galaxies selected from radio to X-ray) or extended (i.e., clusters and gravitational lensing)-in order to measure the bias and redshift distribution of intensities of infrared-emitting dusty star-forming galaxies and active galactic nuclei. By locating HerS in Stripe 82, we maximize the overlap with available and upcoming cosmological surveys. The band-merged catalog contains 3.3 x 10(4) sources detected at a significance of >= 3 sigma (including confusion noise). The maps and catalog are available at http://www.astro.caltech.edu/hers/.
An Improved Photometric Calibration Of The Sloan Digital Sky Survey Imaging Data
(2008-02) Padmanabhan, Nikhil; Schlegel, David J.; Finkbeiner, Douglas P.; Barentine, J. C.; Blanton, Michael R.; Brewington, Howard J.; Gunn, James E.; Harvanek, Michael; Hogg, David W.; Ivezic, Zeljko; Johnston, David; Kent, Stephen M.; Kleinman, S. J.; Knapp, Gillian R.; Krzesinski, Jurek; Long, Dan; Neilsen, Eric H., Jr.; Nitta, Atsuko; Loomis, Craig; Lupton, Robert H.; Roweis, Sam; Snedden, Stephanie A.; Strauss, Michael A.; Tucker, Douglas L.; Barentine, J. C.
We present an algorithm to photometrically calibrate wide-field optical imaging surveys, which simultaneously solves for the calibration parameters and relative stellar fluxes using overlapping observations. The algorithm decouples the problem of "relative'' calibrations from that of "absolute'' calibrations; the absolute calibration is reduced to determining a few numbers for the entire survey. We pay special attention to the spatial structure of the calibration errors, allowing one to isolate particular error modes in downstream analyses. Applying this to the SDSS imaging data, we achieve similar to 1% relative calibration errors across 8500 deg(2) in griz; the errors are similar to 2% for the u band. These errors are dominated by unmodeled atmospheric variations at Apache Point Observatory. These calibrations, dubbed "uber-calibration,'' are now public with SDSS Data Release 6 and will be a part of subsequent SDSS data releases.
Kepler-445, Kepler-446 And The Occurrence Of Compact Multiples Orbiting Mid-M Dwarf Stars
(2015-03) Muirhead, Phillip S.; Mann, Andrew W.; Vanderburg, Andrew; Morton, Timothy D.; Kraus, Adam; Ireland, Michael; Swift, Jonathan J.; Feiden, Gregory A.; Gaidos, Eric; Gazak, J. Zachary; Mann, Andrew W.; Kraus, Adam
We confirm and characterize the exoplanetary systems Kepler-445 and Kepler-446: two mid-M dwarf stars, each with multiple, small, short-period transiting planets. Kepler-445 is a metal-rich ([ Fe/H] = + 0.25 0.10) M4 dwarf with three transiting planets, and Kepler-446 is a metal-poor ([ Fe/H] = -0.30 0.10) M4 dwarf also with three transiting planets. Kepler-445c is similar toGJ 1214b: both in planetary radius and the properties of the host star. The Kepler-446 system is similar to the Kepler-42 system: both are metal-poor with large galactic space velocities and three short-period, likely rocky transiting planets that were initially assigned erroneously large planet-to-star radius ratios. We independently determined stellar parameters from spectroscopy and searched for and fitted the transit light curves for the planets, imposing a strict prior on stellar density in order to remove correlations between the fitted impact parameter and planet-to-star radius ratio for short-duration transits. Combining Kepler-445, Kepler-446, and Kepler-42, and isolating all mid-M dwarf stars observed by Kepler with the precision necessary to detect similar systems, we calculate that 21+ 7 -5 % of mid-M dwarf stars host compact multiples ( multiple planets with periods of less than 10 days) for a wide range of metallicities. We suggest that the inferred planet masses for these systems support highly efficient accretion of protoplanetary disk metals by mid-M dwarf protoplanets.
A Measurement Of The Rate Of Type Ia Supernovae At Redshift Z Approximate To 0.1 From The First Season Of The SDSS-II Supernova Survey
(2008-07) Dilday, Benjamin; Kessler, Richard; Frieman, Joshua A.; Holtzman, Jon; Marriner, John; Miknaitis, Gajus; Nichol, Robert C.; Romani, Roger; Sako, Masao; Bassett, Bruce; Becker, Andrew; Cinabro, David; DeJongh, Fritz; Depoy, Darren L.; Doi, Mamoru; Garnavich, Peter M.; Hogan, Craig J.; Jha, Saurabh; Konishi, Kohki; Lampeitl, Hubert; Marshall, Jennifer L.; McGinnis, David; Prieto, Jose Luis; Riess, Adam G.; Richmond, Michael W.; Schneider, Donald P.; Smith, Mathew; Takanashi, Naohiro; Tokita, Kouichi; van der Heyden, Kurt; Yasuda, Naoki; Zheng, Chen; Barentine, John; Brewington, Howard; Choi, Changsu; Crotts, Arlin; Dembicky, Jack; Harvanek, Michael; Im, Myunshin; Ketzeback, William; Kleinman, Scott J.; Krzesinski, Jurek; Long, Daniel C.; Malanushenko, Elena; Malanushenko, Viktor; McMillan, Russet J.; Nitta, Atsuko; Pan, Kaike; Saurage, Gabrelle; Snedden, Stephanie A.; Watters, Shannon; Wheeler, J. Craig; York, Donald; Wheeler, J. Craig
A Measurement Of The Rate Of Type Ia Supernovae In Galaxy Clusters From The SDSS-II Supernova Survey
(2010-06) Dilday, Benjamin; Bassett, Bruce; Becker, Andrew; Bender, Ralf; Castander, Francisco; Cinabro, David; Frieman, Joshua A.; Galbany, Lluis; Garnavich, Peter; Goobar, Ariel; Hopp, Ulrich; Ihara, Yutaka; Jha, Saurabh W.; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Miquel, Ramon; Molla, Mercedes; Nichol, Robert C.; Nordin, Jakob; Riess, Adam G.; Sako, Masao; Schneider, Donald P.; Smith, Mathew; Sollerman, Jesper; Wheeler, J. Craig; Ostman, Linda; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Dan; Pan, Kaike; Simmons, Audrey; Snedden, Stephanie; Wheeler, J. Craig; Barentine, John
We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z <= 0.17 and 27 SN events in 492 maxBCG clusters at 0.1 <= z <= 0.3. We find values for the cluster SN Ia rate of (0.37(-0.12-0.01)(+0.17+0.01)) SNur h(2) and (0.55(-0.11-0.01)(+0.13+0.02)) SNur h(2) (SNux = 10(-12) Lx(circle dot)(-1)yr(-1)) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be (0.31(-0.12-0.01)(+0.18+0.01)) SNur h(2) and (0.49(-0.11-0.01)(+0.15+0.02)) SNur h(2) in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be (2.04(-1.11-0.04)(+1.99+0.07)) SNur h(2) and (0.36(-0.30-0.01)(+0.84+0.01)) SNur h(2) in C4 and maxBCG clusters, respectively. The ratio of the SN Ia rate in cluster early-type galaxies to that of the SN Ia rate in field early-type galaxies is 1.94(-0.91-0.015)(+1.31+0.043) and 3.02(-1.03-0.048)(+1.31+0.062), for C4 and maxBCG clusters, respectively. The SN rate in galaxy clusters as a function of redshift, which probes the late time SN Ia delay distribution, shows only weak dependence on redshift. Combining our current measurements with previous measurements, we fit the cluster SN Ia rate data to a linear function of redshift, and find r(L) =[(0.49(-0.14)(+0.15))+(0.91(-0.81)(+0.85)) x z] SNuB h(2). A comparison of the radial distribution of SNe in cluster to field early-type galaxies shows possible evidence for an enhancement of the SN rate in the cores of cluster early-type galaxies. With an observation of at most three hostless, intra-cluster SNe Ia, we estimate the fraction of cluster SNe that are hostless to be (9.4(-5.1)(+8.3))%.
The Neptune-Sized Circumbinary Planet Kepler-38B
(2012-10) Orosz, Jerome A.; Welsh, William F.; Carter, Joshua A.; Brugamyer, Erik; Buchhave, Lars A.; Cochran, William D.; Endl, Michael; Ford, Eric B.; MacQueen, Phillip; Short, Donald R.; Torres, Guillermo; Windmiller, Gur; Agol, Eric; Barclay, Thomas; Caldwell, Douglas A.; Clarke, Bruce D.; Doyle, Laurance R.; Fabrycky, Daniel C.; Geary, John C.; Haghighipour, Nader; Holman, Matthew J.; Ibrahim, Khadeejah A.; Jenkins, Jon M.; Kinemuchi, Karen; Li, Jie; Lissauer, Jack J.; Prsa, Andrej; Ragozzine, Darin; Shporer, Avi; Still, Martin; Wade, Richard A.; Brugamyer, Erik; Cochran, William D.; Endl, Michael; MacQueen, Phillip
We discuss the discovery and characterization of the circumbinary planet Kepler-38b. The stellar binary is single-lined, with a period of 18.8 days, and consists of a moderately evolved main-sequence star (M-A = 0.949+/-0.059 M-circle dot and R-A = 1.757+/-0.034 R-circle dot) paired with a low-mass star (M-B = 0.249+/-0.010 M-circle dot and R-B = 0.2724+/-0.0053 R-circle dot) in a mildly eccentric (e = 0.103) orbit. A total of eight transits due to a circumbinary planet crossing the primary star were identified in the Kepler light curve (using Kepler Quarters 1-11), from which a planetary period of 105.595+/-0.053 days can be established. A photometric dynamical model fit to the radial velocity curve and Kepler light curve yields a planetary radius of 4.35+/-0.11 R-circle plus, or equivalently 1.12+/-0.03 R-Nep. Since the planet is not sufficiently massive to observably alter the orbit of the binary from Keplerian motion, we can only place an upper limit on the mass of the planet of 122 M-circle dot(7.11 M-Nep or equivalently 0.384 M-Jup) at 95% confidence. This upper limit should decrease as more Kepler data become available.
New Pulsating DB White Dwarf Stars From The Sloan Digital Sky Survey
(2009-01) Nitta, Atsuko; Kleinman, S. J.; Krzesinski, J.; Kepler, S. O.; Metcalfe, T. S.; Mukadam, Anjum S.; Mullally, Fergal; Nather, R. E.; Sullivan, Denis J.; Thompson, Susan E.; Winget, D. E.; Nather, R. E.; Winget, D. E.
We are searching for new He atmosphere white dwarf pulsators (dbVs) based on the newly found white dwarf stars from the spectra obtained by the Sloan Digital Sky Survey. dbVs pulsate at hotter temperature ranges than their better known cousins, the H atmosphere white dwarf pulsators (DAVs or ZZ Ceti stars). Since the evolution of white dwarf stars is characterized by cooling, asteroseismological studies of dbVs give us opportunities to study white dwarf structure at a different evolutionary stage than the DAVs. The hottest dbVs are thought to have neutrino luminosities exceeding their photon luminosities, a quantity measurable through asteroseismology. Therefore, they can also be used to study neutrino physics in the stellar interior. So far we have discovered nine new dbVs, doubling the number of previously known dbVs. Here we report the new pulsators' light curves and power spectra.
On The Rates Of Type Ia Supernovae In Dwarf And Giant Hosts With ROTSE-IIIb
(2012-12) Quimby, Robert M.; Yuan, Fang; Akerlof, Carl; Wheeler, J. Craig; Warren, Michael S.; Wheeler, J. Craig
We present a sample of 23 spectroscopically confirmed Type Ia supernovae (SNe Ia) that were discovered in the background of galaxy clusters targeted by ROTSE-IIIb and use up to 18 of these to determine the local ((z) over bar = 0.05) volumetric rate. Since our survey is flux limited and thus biased against fainter objects, the pseudo-absolute magnitude distribution (pAMD) of SNe Ia in a given volume is an important concern, especially the relative frequency of high-to low-luminosity SNe Ia. We find that the pAMD derived from the volume-limited Lick Observatory Supernova Search (LOSS) sample is incompatible with the distribution of SNe Ia in a volume-limited (z < 0.12) sub-sample of the Sloan Digital Sky Survey II (SDSS-II). The LOSS sample requires far more low-luminosity SNe Ia than the SDSS-II can accommodate. Even though LOSS and SDSS-II have sampled different SNe Ia populations, their volumetric rates are surprisingly similar. Using the same model pAMD adopted in the SDSS-II SNe Ia rate calculation and excluding two high-luminosity SNe Ia from our sample, we derive a rate that is marginally higher than previous low-redshift determinations. With our full sample and the LOSS pAMD, our rate is more than double the canonical value. We also find that 5 of our 18 SNe Ia are hosted by very low luminosity (M-B > -16) galaxies, whereas only 1 out of 79 nearby SDSS-II SNe Ia have such faint hosts. It is possible that previous works have undercounted either low-luminosity SNe Ia, SNe Ia in low-luminosity hosts, or peculiar SNe Ia (sometimes explicitly), and the total SNe Ia rate may be higher than the canonical value.
A Petal Of The Sunflower: Photometry Of The Stellar Tidal Stream In The Halo Of Messier 63 (NGC 5055)
(2011-11) Chonis, Taylor S.; Martinez-Delgado, David; Gabany, R. Jay; Majewski, Steven R.; Hill, Gary J.; Gralak, Ray; Trujillo, Ignacio; Hill, Gary J.
We present deep surface photometry of a very faint, giant arc-loop feature in the halo of the nearby spiral galaxy NGC 5055 (M63) that is consistent with being a part of a stellar stream resulting from the disruption of a dwarf satellite galaxy. This faint feature was first detected in early photographic studies by van der Kruit; more recently, in the study of Martinez-Delgado and as presented in this work, from the loop has been realized to be the result of a recent minor merger through evidence obtained by wide-field, deep images taken with a telescope of only 0.16 m aperture. The stellar stream is clearly confirmed in additional deep images taken with the 0.5 m telescope of the BlackBird Remote Observatory and the 0.8 m telescope of the McDonald Observatory. This low surface brightness (mu(R) approximate to 26 mag arcsec(-2)) arc-like structure around the disk of the galaxy extends 14'0 (similar to 29 kpc projected) from its center, with a projected width of 1'6 (similar to 3.3 kpc). The stream's morphology is consistent with that of the visible part of a giant, >great-circle> type stellar stream originating from the recent accretion of a similar to 10(8) M-circle dot dwarf satellite in the last few Gyr. The progenitor satellite's current position and final fate are not conclusive from our data. The color of the stream's stars is consistent with dwarfs in the Local Group and is similar to the outer faint regions of M63's disk and stellar halo. From our photometric study, we detect other low surface brightness >plumes;> some of these may be extended spiral features related to the galaxy's complex spiral structure, and others may be tidal debris associated with the disruption of the galaxy's outer stellar disk as a result of the accretion event. We are able to differentiate between features related to the tidal stream and faint, blue extended features in the outskirts of the galaxy's disk previously detected by the Galaxy Evolution Explorer satellite. With its highly warped Hi gaseous disk (similar to 20 degrees), M63 represents one of the several examples of an isolated spiral galaxy with a warped disk showing recently discovered strong evidence of an ongoing minor merger.
Photometric Variability In A Warm, Strongly Magnetic Dq White Dwarf, SDSS J103655.39+652252.2
(2013-06) Williams, Kurtis A.; Winget, D. E.; Montgomery, Michael H.; Dufour, Patrick; Kepler, S. O.; Hermes, J. J.; Falcon, Ross E.; Winget, K. I.; Bolte, Michael; Rubin, Kate H. R.; Liebert, James; Winget, D. E.; Montgomery, Michael H.; Hermes, J. J.; Falcon, Ross E.; Winget, K. I.
We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude 0.442% +/- 0.024%; no other periodic modulations are observed with amplitudes greater than or similar to 0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: T-eff approximate to 15,500 K, log g approximate to 9, log(C/He) = -1.0, and a mean magnetic field strength of 3.0 +/- 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, helium-dominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same.
Planetary Candidates Observed by Kepler. III. Analysis of the First 16 Months of Data
(2013-02) Batalha, Natalie M.; Rowe, Jason F.; Bryson, Stephen T.; Barclay, Thomas; Burke, Christopher J.; Caldwell, Douglas A.; Christiansen, Jessie L.; Mullally, Fergal; Thompson, Susan E.; Brown, Timothy M.; Dupree, Andrea K.; Fabrycky, Daniel C.; Ford, Eric B.; Fortney, Jonathan J.; Gilliland, Ronald L.; Isaacson, Howard; Latham, David W.; Marcy, Geoffrey W.; Quinn, Samuel N.; Ragozzine, Darin; Shporer, Avi; Borucki, William J.; Ciardi, David R.; Gautier, Thomas N., III; Haas, Michael R.; Jenkins, Jon M.; Koch, David G.; Lissauer, Jack J.; Rapin, William; Basri, Gibor S.; Boss, Alan P.; Buchhave, Lars A.; Carter, Joshua A.; Charbonneau, David; Christensen-Dalsgaard, Joergen; Clarke, Bruce D.; Cochran, William D.; Demory, Brice-Olivier; Desert, Jean-Michel; Devore, Edna; Doyle, Laurance R.; Esquerdo, Gilbert A.; Everett, Mark; Fressin, Francois; Geary, John C.; Girouard, Forrest R.; Gould, Alan; Hall, Jennifer R.; Holman, Matthew J.; Howard, Andrew W.; Howell, Steve B.; Ibrahim, Khadeejah A.; Kinemuchi, Karen; Kjeldsen, Hans; Klaus, Todd C.; Li, Jie; Lucas, Philip W.; Meibom, Soren; Morris, Robert L.; Prsa, Andrej; Quintana, Elisa; Sanderfer, Dwight T.; Sasselov, Dimitar; Seader, Shawn E.; Smith, Jeffrey C.; Steffen, Jason H.; Still, Martin; Stumpe, Martin C.; Tarter, Jill C.; Tenenbaum, Peter; Torres, Guillermo; Twicken, Joseph D.; Uddin, Kamal; Van Cleve, Jeffrey; Walkowicz, Lucianne; Welsh, William F.; Cochran, William D.
New transiting planet candidates are identified in 16 months (2009 May-2010 September) of data from the Kepler spacecraft. Nearly 5000 periodic transit-like signals are vetted against astrophysical and instrumental false positives yielding 1108 viable new planet candidates, bringing the total count up to over 2300. Improved vetting metrics are employed, contributing to higher catalog reliability. Most notable is the noise-weighted robust averaging of multiquarter photo-center offsets derived from difference image analysis that identifies likely background eclipsing binaries. Twenty-two months of photometry are used for the purpose of characterizing each of the candidates. Ephemerides (transit epoch, T-0, and orbital period, P) are tabulated as well as the products of light curve modeling: reduced radius (R-P / R-star), reduced semimajor axis (d / R-star), and impact parameter (b). The largest fractional increases are seen for the smallest planet candidates (201% for candidates smaller than 2R(circle plus). compared to 53% for candidates larger than 2R.) and those at longer orbital periods (124% for candidates outside of 50 day orbits versus 86% for candidates inside of 50 day orbits). The gains are larger than expected from increasing the observing window from 13 months (Quarters 1-5) to 16 months (Quarters 1-6) even in regions of parameter space where one would have expected the previous catalogs to be complete. Analyses of planet frequencies based on previous catalogs will be affected by such incompleteness. The fraction of all planet candidate host stars with multiple candidates has grown from 17% to 20%, and the paucity of short-period giant planets in multiple systems is still evident. The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the habitable zone are forthcoming if, indeed, such planets are abundant.
Planetary Candidates Observed By Kepler. V. Planet Sample from Q1-Q12 (36 Months)
(2015-03) Rowe, Jason F.; Coughlin, Jeffrey L.; Antoci, Victoria; Barclay, Thomas; Batalha, Natalie M.; Borucki, William J.; Burke, Christopher J.; Bryson, Steven T.; Caldwell, Douglas A.; Campbell, Jennifer R.; Catanzarite, Joseph H.; Christiansen, Jessie L.; Cochran, William; Gilliland, Ronald L.; Girouard, Forrest R.; Haas, Michael R.; Helminiak, Krzysztof G.; Henze, Christopher E.; Hoffman, Kelsey L.; Howell, Steve B.; Huber, Daniel; Hunter, Roger C.; Jang-Condell, Hannah; Jenkins, Jon M.; Klaus, Todd C.; Latham, David W.; Li, Jie; Lissauer, Jack J.; McCauliff, Sean D.; Morris, Robert L.; Mullally, F.; Ofir, Aviv; Quarles, Billy; Quintana, Elisa; Sabale, Anima; Seader, Shawn; Shporer, Avi; Smith, Jeffrey C.; Steffen, Jason H.; Still, Martin; Tenenbaum, Peter; Thompson, Susan E.; Twicken, Joseph D.; Van Laerhoven, Christa; Wolfgang, Angie; Zamudio, Khadeejah A.; Cochran, William D.
The Kepler mission discovered 2842 exoplanet candidates with 2 yr of data. We provide updates to the Kepler planet candidate sample based upon 3 yr (Q1-Q12) of data. Through a series of tests to exclude false-positives, primarily caused by eclipsing binary stars and instrumental systematics, 855 additional planetary candidates have been discovered, bringing the total number known to 3697. We provide revised transit parameters and accompanying posterior distributions based on a Markov Chain Monte Carlo algorithm for the cumulative catalog of Kepler Objects of Interest. There are now 130 candidates in the cumulative catalog that receive less than twice the flux the Earth receives and more than 1100 have a radius less than 1.5 R-circle plus. There are now a dozen candidates meeting both criteria, roughly doubling the number of candidate Earth analogs. A majority of planetary candidates have a high probability of being bonafide planets, however, there are populations of likely false-positives. We discuss and suggest additional cuts that can be easily applied to the catalog to produce a set of planetary candidates with good fidelity. The full catalog is publicly available at the NASA Exoplanet Archive.