Girven, Jonathan, Gaensicke, B. T., Steeghs, D. and Koester, Detlev (2011) DA white dwarfs in Sloan Digital Sky Survey Data Release 7 and a search for infrared excess emission. Monthly Notices of the Royal Astronomical Society, Vol.417 (No.2). pp. 1210-1235. doi:10.1111/j.1365-2966.2011.19337.x

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Abstract

We present a method which uses colour–colour cuts on the Sloan Digital Sky Survey (SDSS) photometry to select white dwarfs with hydrogen-rich (DA) atmospheres without the recourse to spectroscopy. This method results in a sample of DA white dwarfs that is 95 per cent complete at an efficiency of returning a true DA white dwarf of 62 per cent. The approach was applied to SDSS Data Release 7 for objects with and without SDSS spectroscopy. This led to 4636 spectroscopicially confirmed DA white dwarfs with g≤ 19; a ∼70 per cent increase compared to Eisenstein et al.’s 2006 sample. Including the photometric-only objects, we estimate a factor of 3 increase in DA white dwarfs. We find that the SDSS spectroscopic follow-up is 44 per cent complete for DA white dwarfs with Teff≳ 8000 K. We further cross-correlated the SDSS sample with Data Release 8 of the UKIRT (United Kingdom Infrared Telescope) Infrared Deep Sky Survey (UKIDSS) Large Area Survey. The spectral energy distributions (SED) of both subsets, with and without SDSS spectroscopy, were fitted with white dwarf models to determine the fraction of DA white dwarfs with low-mass stellar companions or dusty debris discs via the detection of excess near-infrared emission. From the spectroscopic sample we find that 2.0 per cent of white dwarfs have an excess consistent with a brown dwarf type companion, with a firm lower limit of 0.8 per cent. From the white dwarfs with photometry only, we find that 1.8 per cent are candidates for having brown dwarf companions. Similarly, both samples show that ∼1 per cent of white dwarfs are candidates for having a dusty debris disc.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Brown dwarf stars, Circumstellar matter, White dwarf stars, Low mass stars, Infrared telescopes
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Wiley
ISSN:	0035-8711
Official Date:	October 2011
Dates:	Date Event October 2011 Published
Volume:	Vol.417
Number:	No.2
Page Range:	pp. 1210-1235
DOI:	10.1111/j.1365-2966.2011.19337.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Alfred P. Sloan Foundation, National Science Foundation (U.S.) (NSF), United States. Dept. of Energy, United States. National Aeronautics and Space Administration (NASA), Japan. Monbu Kagakushō [Japan. Ministry of Education, Culture, Sports, Science and Technology] (MK), Max-Planck-Gesellschaft zur Förderung der Wissenschaften [Max Planck Society for the Advancement of Science], Higher Education Funding Council for England (HEFCE), Science and Technology Facilities Council (Great Britain) (STFC), American Museum of Natural History, Universität Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermi National Accelerator Laboratory (Fermilab), Princeton University. Institute for Advanced Study, Johns Hopkins University, Joint Institute for Nuclear Astrophysics, Kavli Institute for Particle Astrophysics and Cosmology, Zhongguo ke xue yuan [Chinese Academy of Sciences] (CAS), Leibniz-Institut für Astrophysik Potsdam, Los Alamos National Laboratory (LANL), Max-Planck-Institut für Astronomie, Max-Planck-Institut für Astrophysik, New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, United States Naval Observatory, University of Washington

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