New ZZ Ceti Stars from the LAMOST Survey

Abstract

The spectroscopic sky survey carried out by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) provides the largest stellar spectra library in the world to date. A large number of new DA white dwarfs had been identified based on the LAMOST spectra. The effective temperature ( ) and surface gravity ( ) of most DA white dwarfs were determined and published in the catalogs. We selected ZZ Ceti candidates from the published catalogs by considering whether their are situated in the ZZ Ceti instability strip. The follow-up time-series photometric observations for the candidates were performed in 2015 and 2016. Four stars: LAMOST J004628.31+343319.90, LAMOST J062159.49+252335.9, LAMOST J010302.46+433756.2, and LAMOST J013033.90+273757.9 are finally confirmed to be new ZZ Ceti stars. They show dominant peaks with amplitudes rising above the 99.9% confidence level in the amplitude spectra. As LAMOST J004628.31+343319.90 has an estimated mass of ∼0.40 , and LAMOST J013033.90+273757.9 has a mass of ∼0.45 derived from their values, these two stars are inferred to be potential helium-core white dwarfs.