2000A&A...355..291V

We report the discovery of a new pulsating DA white dwarf, or ZZ Ceti, from the list of the Palomar-Green survey, rediscovered in the ongoing Hamburg Quasar survey (HQS). PG 1541+650 is one of the ZZ Ceti candidates listed in the analysis of 80 DA white dwarfs from the HQS. With an effective temperature of 12000K, for a surface gravity logg=7.79, it lies in the ZZ Ceti instability strip. It is indeed a ZZ Ceti star of large amplitude with at least three frequencies: the main mode has a frequency of 1.450mHz (689s period) with a relative amplitude of 0.045, with the other modes at 1.773mHz (564s period) and at 1.312mHz (757s) having smaller relative amplitudes of 0.015 and 0.014 respectively. The first harmonics of the dominant mode is seen at 2.911mHz. According to its atmospheric parameters, PG 1541+650 is the lowest mass recorded ZZ Ceti (0.5M_☉) and should be close to the instability strip blue edge corresponding to its mass. If it is so, its rather long periods and large amplitudes do not fit with the general period-temperature and/or amplitude-temperature correlations.