PG1541+650: A new ZZ Ceti white dwarf

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). PG1541+650 is one of the ZZ Ceti candidates listed in the analysis of 80 DA white dwarfs from the HQS. With an effective temperat ure of 12000 K, for a surface gravity log g=7.79, it lies in the ZZ Ceti in stability strip. It is indeed a ZZ Ceti star of large amplitude with at lea st three frequencies: the main mode has a frequency of 1.450 mHz (689 s per iod) with a relative amplitude of 0.045, with the other modes at 1.773 mHz (564 s period) and at 1.312 mHz (757 s) having smaller relative amplitudes of 0.015 and 0.014 respectively. The first harmonics of the dominant mode i s seen at 2.911 mHz. According to its atmospheric parameters, PG1541+650 is the lowest mass recorded ZZ Ceti (0.5 M.) and should be close to the insta bility strip blue edge corresponding to its mass. If it is so, its rather l ong periods and large amplitudes do not fit with the general period-tempera ture and/or amplitude-temperature correlations.