White Dwarfs with Infrared Excess from LAMOST Data Release 5

Abstract

Infrared (IR) excess is an important probe for substellar companions and/or debris disks around white dwarfs (WDs). Such systems are still rare, so an in-depth understanding of their formation and long-term evolution has yet to be developed. One of the largest spectroscopic surveys, carried out by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), has recently released more than 3000 WDs, a significant fraction of which have not been searched for IR excess. Here, we present a cross-correlation between the LAMOST Data Release 5 WD catalog and Pan-STARRS, the Sloan Digital Sky Survey (SDSS), the UKIRT Infrared Deep Sky Survey, the Two-Micron All Sky Survey (2MASS), and the Wide-field Infrared Survey Explorer (WISE). By performing spectral energy distribution fittings for 846 WDs with WISE detections, we identify 50 candidates with IR excess, including seven candidate WD+M dwarf binaries, 31 candidate WD+brown dwarf (BD) binaries, and 12 candidate WD+dust disk systems. Eight of the dust disk systems are our new identifications. By utilizing a systematic survey with accurate stellar parameters derived from spectral fitting, our work is an important addition to previous searches for IR excess from SDSS and Gaia WDs, and it provides a significant (≳8%) complement to the current database of WDs with candidate BD companions and dust disks. The frequencies of the WD+BD binaries and the WD+dust disk systems are constrained to be ≲3.7% and ∼1.4%, respectively. The properties of the candidate dust disk systems are discussed. All of our candidates require follow-up observations for confirmation, owing to the limited spatial resolution of WISE.

Keywords

• White dwarf stars
• Brown dwarfs
• Infrared excess
• Debris disks
• Circumstellar dust