White dwarfs identified in LAMOST Data Release 5

Kavli Affiliate: Huawei Zhang

| First 5 Authors: Jincheng Guo, Jingkun Zhao, Huawei Zhang, Jiajun Zhang, Yu Bai

| Summary:

In this paper, we report white dwarfs identified in the 5th Data Release of
the Large Area Multi-Object fibre Spectroscopic Telescope, including spectral
types of DA, DB, DC, DZ, and so on. There are 2 625 DA spectra of 2 281 DA
stars, 182 DB spectra of 166 DB stars, 62 DC spectra of 58 DC stars, 36 DZ
spectra of 33 DZ stars and many other types identified, in addition to our
previous paper (Data Release 2). Among those sources, 393 DA stars and 46 DB
stars are new identifications after cross-matching with the literature. In
order to select DA candidates, we use the classification result from the LAMOST
pipeline, colour-colour cut method and a random forest machine learning method.
For DBs, since there is no template for DB in the pipeline model, a random
forest machine learning method is chosen to select candidates. All the WD
candidates have been visually checked individually. The parameters of effective
temperature, surface gravity, mass, and cooling age have been estimated for
relatively high signal-to-noise ratio DAs and DBs. The peaks of the DA and DB
mass distributions are found to be around 0.62Msun and 0.65Msun, respectively.
Finally, the data and method we used to select white dwarf candidates for the
second phase of LAMOST survey are also addressed in this paper.

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