70 DA White Dwarfs Identified in LAMOST Pilot Survey

Jingkun Zhao, Gang Zhao, Ali Luo and T. D. Oswalt present a spectroscopically identified catalog of 70 DA white dwarfs (WDs) from the LAMOST pilot survey. Thirty-five are found to be new identifications after cross-correlation with the Eisenstein et al. and Villanova catalogs. The effective temperature and gravity of these WDs are estimated by Balmer lines fitting. Most of them are hot WDs. The cooling times and masses of these WDs are estimated by interpolation in theoretical evolution tracks. The peak of the mass distribution is found to be ~0.6 M ⊙, which is consistent with prior work in the literature. The distances of these WDs are estimated using the method of synthetic spectral distances. All of these WDs are found to be in the Galactic disk from our analysis of space motions. Our sample supports the expectation that WDs with high mass are concentrated near the plane of the Galactic disk.

Fig. 1. A comparison of typical SDSS and LAMOST pilot survey WD spec tra for star J100316.35-002336.95. In the top panel, the solid line is the LAMOST s pectrum while dotted line is that from SDSS. The bottom panel presents the residule betw een the two spectra.

Fig. 2. Fits of the observed Balmer lines for J150156.26+302300.13. Lines range from H β (bottom) to H8 (top). The solid black line is the observed spectra wh ile the dashed line is the model spectra.