White dwarfs identified in LAMOST DR 2

Abstract

Here we present a catalogue of 1056 spectroscopically identified hydrogen-dominated white dwarfs (DAWDs), 34 helium-dominated white dwarfs (DBWDs) and 276 white dwarf main sequence (WDMS) binaries from the Large sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey data release 2 (DR2). 383 DAWDs, 4 DBWDs and 138 WDMSs are new identifications after cross-match with literature. There are ~4100 k spectra in total from DR 2. The low ratio of white dwarfs found in LAMOST is attributed to biased selection of LAMOST input catalogue and much brighter targets relative to stars observed in Sloan Digital Sky Survey. In this paper, a new DAWD selection method is adopted as a new attempt and supplement to the traditional methods. The effective temperature, surface gravity, mass, cooling age and distance of high signal-to-noise DAWDs are estimated. The peak of the mass distribution is found to be ~0.6 M·, which is consistent with previous work. The parameters of WDMS binaries are also provided in this paper. As the foundation of our future work, which is to identify more WDs with debris disc, WDs found in LAMOST showed a lot of potential. Interesting infrared-excess WDs will be reported in our forthcoming paper.