Mon. Not. R. Astron. Soc., 416, 2768-2791 (2011/October-1)
White dwarfs in the UKIRT infrared deep sky survey large area survey: the substellar companion fraction.
STEELE P.R., BURLEIGH M.R., DOBBIE P.D., JAMESON R.F., BARSTOW M.A. and SATTERTHWAITE R.P.
Abstract (from CDS):
We present a near-infrared photometric search for unresolved substellar companions and debris discs around white dwarfs in the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey. We cross-correlate the Sloan Digital Sky Survey (SDSS) DR4 and McCook & Sion catalogues of white dwarfs with the UKIDSS DR8 producing 3109 and 163 unique matches, respectively. Cooling models are fitted to the optical photometry of a subsample of DA white dwarfs and extended to the near-infrared. A comparison is then made with the observed photometry to identify those stars with a near-infrared excess consistent with the presence of a cool companion or debris disc. Where present, we have estimated the approximate spectral type of any putative companion, or an upper limit on the temperature of a debris disc. In total we identify 14–16 new candidate white dwarf + very low mass stellar systems, 9–11 candidate white dwarf + brown dwarf systems, and three candidate white dwarf + debris discs. We place lower limits on the unresolved (<2 arcsec) companions to all DA white dwarfs and thus assess the sensitivity of UKIDSS to such objects. We use this result to estimate unresolved binary fractions of f_WD + dL_≥ 0.4±0.3 per cent, f_ WD + dT_≥ 0.2 per cent and f_ WD + BD_≥ 0.5±0.3 per cent.
2011 The Authors Monthly Notices of the Royal Astronomical Society2011 RAS
brown dwarfs - stars: low-mass - white dwarfs - infrared: stars
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