- ID:
- ivo://CDS.VizieR/J/ApJS/167/40
- Title:
- SDSS4 confirmed white dwarfs catalog
- Short Name:
- J/ApJS/167/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 9316 spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey Data Release 4. We have selected the stars through photometric cuts and spectroscopic modeling, backed up by a set of visual inspections. About 6000 of the stars are new discoveries, roughly doubling the number of spectroscopically confirmed white dwarfs. We analyze the stars by performing temperature and surface gravity fits to grids of pure hydrogen and helium atmospheres. Among the rare outliers are a set of presumed helium-core DA white dwarfs with estimated masses below 0.3M_{sun}_, including two candidates that may be the lowest-mass yet found. We also present a list of 928 hot subdwarfs.
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- ID:
- ivo://CDS.VizieR/J/ApJ/869/122
- Title:
- SDSS-DR14 and LAMOST DR6 spectra in GD-1 stream
- Short Name:
- J/ApJ/869/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining data from Gaia DR2, SDSS DR14, and LAMOST DR6, we update the fit to model of the properties of the stellar stream GD-1 and find that it has an age of ~13Gyr, [Fe/H] of -2.2+/-0.12, and a distance from the Sun of ~8kpc. We tabulate six-dimensional (6D) phase-space fiducial points along the GD-1 stream orbit over a 90{deg} arc. The fitted orbit shows that the stream has an eccentricity e~0.3, perigalacticon of 14.2kpc, apogalacticon of 27.0kpc, and inclination i~40{deg}. There is evidence along the arc for four candidate stellar overdensities, one candidate gap, two candidate stellar underdensities, and that the stream is cut off at {phi}_1_~2{deg} (in the stream-aligned ({phi}_1_, {phi}_2_) coordinate system of Koposov+ 2010ApJ...712..260K). The spur originating at {phi}_1_~-40{deg} implies stars were pulled away from the stream trace by an encounter (potentially a dark matter subhalo). The narrowest place (FWHM~44.6pc) of the GD-1 trace is at ({phi}_1_, {phi}2^c^)~(-14{deg}, 0.15{deg}), which is ~(178.18{deg}, 52.19{deg}) in (RA, DE), where the progenitor is possibly located. We also find six blue horizontal branch and 10 blue stragglers spectroscopic stars in the GD-1 stream.
- ID:
- ivo://CDS.VizieR/J/AJ/135/785
- Title:
- SDSS-DR5 low-mass star spectroscopic sample
- Short Name:
- J/AJ/135/785
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic analysis of over 38000 low-mass stars from the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Analysis of this unprecedentedly large sample confirms the previously detected decrease in the fraction of magnetically active stars (as traced by H{alpha} emission) as a function of vertical distance from the Galactic Plane. The magnitude and slope of this effect varies as a function of spectral type. Using simple 1-D dynamical models, we demonstrate that the drop in activity fraction can be explained by thin disk dynamical heating and a rapid decrease in magnetic activity. The timescale for this rapid activity decrease changes according to the spectral type. By comparing our data to the simulations, we calibrate the age-activity relation at each M dwarf spectral type. We also present evidence for a possible decrease in the metallicity as a function of height above the Galactic Plane. In addition to our activity analysis, we provide line measurements, molecular band indices, colors, radial velocities, 3-D space motions and mean properties as a function of spectral type for the SDSS DR5 low-mass star sample.
- ID:
- ivo://CDS.VizieR/J/ApJS/204/5
- Title:
- SDSS DR7 white dwarf catalog
- Short Name:
- J/ApJS/204/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new catalog of spectroscopically confirmed white dwarf stars from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic catalog. We find 20407 white dwarf spectra, representing 19712 stars, and provide atmospheric model fits to 14120 DA and 1011 DB white dwarf spectra from 12843 and 923 stars, respectively. These numbers represent more than a factor of two increase in the total number of white dwarf stars from the previous SDSS white dwarf catalogs based on DR4 data. Our distribution of subtypes varies from previous catalogs due to our more conservative, manual classifications of each star in our catalog, supplementing our automatic fits. In particular, we find a large number of magnetic white dwarf stars whose small Zeeman splittings mimic increased Stark broadening that would otherwise result in an overestimated logg if fit as a non-magnetic white dwarf. We calculate mean DA and DB masses for our clean, non-magnetic sample and find the DB mean mass is statistically larger than that for the DAs.
- ID:
- ivo://CDS.VizieR/J/AJ/132/676
- Title:
- SDSS hot DB white dwarfs
- Short Name:
- J/AJ/132/676
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ugriz photometry and optical spectroscopy for 28 DB and DO white dwarfs with temperatures between 28000 and 45000K. About 10 of these are particularly well observed; the remainder are candidates. These are the hottest DB stars yet found, and they populate the DB gap between the hotter DO stars and the familiar DB stars cooler than 30000K. Nevertheless, after carefully matching the survey volumes we find that the ratio of DA stars to DB stars is a factor of 2.5 larger at 30000 than at 20000K, suggesting that the DB gap is indeed deficient and that some kind of atmospheric transformation takes place in roughly 10% of DA stars as they cool from 30000 to 20000K.
- ID:
- ivo://CDS.VizieR/J/MNRAS/382/515
- Title:
- SDSS ultracool and halo WD candidates
- Short Name:
- J/MNRAS/382/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A 2.5x100{deg}^2^ region along the celestial equator (Stripe 82) has been imaged repeatedly from 1998 to 2005 by the Sloan Digital Sky Survey (SDSS). A new catalogue of ~4 million light-motion curves, together with over 200 derived statistical quantities, for objects in Stripe 82 brighter than r~21.5 has been constructed by combining these data by Bramich et al. (2008MNRAS.386..887B). This catalogue is at present the deepest catalogue of its kind. Extracting ~130000 objects with highest signal-to-noise ratio proper motions, we build a reduced proper motion diagram to illustrate the scientific promise of the catalogue. In this diagram, disc and halo subdwarfs are well-separated from the cool white dwarf sequence. Our sample of 1049 cool white dwarf candidates includes at least eight and possibly 21 new ultracool H-rich white dwarfs (Teff<4000K) and one new ultracool He-rich white dwarf candidate identified from their SDSS optical and UKIDSS infrared photometry. At least 10 new halo white dwarfs are also identified from their kinematics.
- ID:
- ivo://CDS.VizieR/I/34
- Title:
- Second Greenwich Catalog of Stars for 1925.0
- Short Name:
- I/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observations for these two catalogs were made with the transit circle at the Royal Observatory in Greenwich, England, between the years 1922 and 1930 under the direction of Sir Frank Dyson, Astronomer Royal. Part I contains fundamental stars contained in the annual volumes of Greenwich Observations of the Sun, Moon and Planets. In addition, 232 stars observed at the prime vertical, South of +32dDec., have been observed. Part II contains all stars down to 7.9 mag in the A.G. scale between the limits of 32d and 64d Dec with the addition of 285 fainter stars in the sparse region of the sky from 12h to 16h RA. From internal information, the probable error of one observation of a star is found to be +/-0.35 arcsec in RA and +/-0.28 arcsec in DE. As the number of observations is generally 5, the pe of a position in the catalog, apart from systematic errors, should be +/-0.15 arcsec. In determining the proper motion of the fundamental stars, the positions of this catalogue were combined with the First Greenwich Catalog of Stars for 1925.0 (Observed 1915-1921), the two Pulkova Catalogues and the two Cape Catalogues preceding this catalogue. Note that the problable errors on the proper motions are not included in this electronic version.
- ID:
- ivo://CDS.VizieR/J/A+AS/103/427
- Title:
- Second Quito Astrolabe Catalogue
- Short Name:
- J/A+AS/103/427
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper contains 515 individual corrections {DELTA}{alpha} and 235 corrections {DELTA}{delta} to FK5 and FK5Supp. stars and 50 corrections to their proper motions computed from observations made with the classical Danjon astrolabe OPL-13 at Quito Astronomical Observatory of Ecuador National Polytechnical School during a period from 1964 to 1983. These corrections cover the declination zone from -30{deg} to +30{deg}. Mean probable errors of catalogue positions are 0.047" in {alpha}cos{delta} and 0.054" in {delta}. The systematic trends of the catalogue {DELTA}{alpha}{alpha}cos{delta}, {DELTA}{alpha}{delta}cos{delta}, {DELTA}{delta}{alpha}, {DELTA}{delta}{delta} are presented for the observed zone.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/154
- Title:
- Sgr stream K- & M-giants and BHB stars
- Short Name:
- J/ApJ/886/154
- Date:
- 07 Dec 2021 13:01:04
- Publisher:
- CDS
- Description:
- We characterize the kinematic and chemical properties of ~3000 Sagittarius (Sgr) stream stars, including K-giants, M-giants, and blue horizontal branch stars (BHBs), selected from SEGUE-2, Large Sky Area Multi-Object Fibre Spectroscopic Telescope, and Sloan Digital Sky Survey separately in Integrals-of-Motion space. The orbit of the Sgr stream is quite clear from the velocity vector in the X-Z plane. Stars traced by K-giants and M-giants show that the apogalacticon of the trailing steam is ~100kpc. The metallicity distributions of Sgr K-giants, M-giants, and BHBs indicate that the M-giants are on average the most metal-rich population, followed by K-giants and BHBs. All of the K-giants, M-giants, and BHBs indicate that the trailing arm is on average more metal-rich than the leading arm, and the K-giants show that the Sgr debris is the most metal-poor part. The {alpha}-abundance of Sgr stars exhibits a similar trend with the Galactic halo stars at lower metallicity ([Fe/H]<~-1.0dex), and then evolve down to lower [{alpha}/Fe] than disk stars at higher metallicity, which is close to the evolution pattern of the {alpha}-element of Milky Way dwarf galaxies. We find that VY and metallicity of K-giants have gradients along the direction of the line of sight from the Galactic center in the X-Z plane, and the K-giants show that VY increases with metallicity at [Fe/H]>~-1.5dex. After dividing the Sgr stream into bright and faint streams according to their locations in equatorial coordinates, the K-giants and BHBs show that the bright and faint streams present different VY and metallicities, the bright stream is on average higher in VY and metallicity than the faint stream.
- ID:
- ivo://CDS.VizieR/J/PAZh/41/896
- Title:
- Short- and long-term pm of close dwarfs
- Short Name:
- J/PAZh/41/896
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Motions of 1308 stars with large proper motions ({mu}>300mas/yr) up to 17 mag were investigated using the results of observations conducted with Pulkovo Normal Astrograph and images taken from data bases of sky surveys (DSS, SDSS DR12, WISE). Basic idea of search of double stars with this material is a comparison between long-term proper motion (POSS2-POSS1, epoch difference is about 50yr) and short-term proper motion (2MASS, SDSS, WISE, Pulkovo, epoch difference is about 10yr). Star is classified as delta-mu-binary candidate in the case of statistically significant difference of short-term and long-term proper motions. This condition is realised for 121 stars of our target list. Additional evidence of duplicity was obtained with comparison of our proper motions with data of several parallax determination programs. Analysis of accurate SDSS photometric values of our stars allows us to conclude that four stars (J0656+3827, J0838+3940, J1229+5332, J2330+4639) are probably binary systems which consist of wite dwarf + M-dwarf.
