Two new ZZ Ceti pulsators from the HS and HE surveys

Abstract

We report the detection of nonradial g-mode oscillations in the DA white dwarfs HS 1039+4112 (B = 15.9) and HE 1429-0343 (B = 15.8) from time-series photometry made at the Loiano 1.5 m telescope. The two stars were previously selected as probable pulsators based on two-color photometry and spectral analysis respectively. Following our temperature and surface gravity determinations, HS 1039+4112 (T-eff = 11 200 K, log g = 8.2) is located near the red edge of the ZZ Ceti instability strip, whereas HE 1429-0343 (T-eff = 11 400 K, log g = 7.8) falls in the middle of the strip. Both stars show a multi-mode behavior with the main periods at about 850 and 970 s respectively, and relatively large amplitudes (similar to 7% and similar to 2.5%).