VAUCLAIR G., DOLEZ N., FU J.-N., HOMEIER D., ROQUES S., CHEVRETON M. and KOESTER D.
Abstract (from CDS):
We report the discovery of a new ZZ Ceti type star 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 12000 K, for the surface gravity log g = 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 1.450 mHz (689 s period) with a relative amplitude of 0.045. Other modes are present at 1.773 mHz (564 s period) and at 1.312 mHz (757 s) with smaller amplitudes. The first harmonics of the dominant mode is seen at 2.911 mHz. According to its atmospheric parameters, PG 1541+650 is the lowest mass recorded ZZ Ceti star(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 amplitude do not fit with the general period-temperature and/or amplitude-temperature correlations.