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Astron. Astrophys. 355, 291-294 (2000)

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PG1541+650: A new ZZ Ceti white dwarf *

G. Vauclair 1, N. Dolez 1, J.-N. Fu 1, D. Homeier 3, S. Roques 1, M. Chevreton 2 and D. Koester 3

1 Laboratoire d'Astrophysique, Observatoire Midi-Pyrénées, 14 avenue E. Belin, 31400 Toulouse, France
2 DAEC, Observatoire de Paris-Meudon, 92195 Meudon, France
3 Institut für Theoretische Physik und Astrophysik, 24098 Kiel, Germany

Received 19 November 1999 / Accepted 5 January 2000

Abstract

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 temperature of 12000 K, 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 1.450 mHz (689 s period) 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 is seen at 2.911 mHz. According to its atmospheric parameters, PG1541+650 is the lowest mass recorded ZZ Ceti (0.5[FORMULA]) 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.

Key words: stars: white dwarfs

* Based on observations obtained at the Telescope Bernard Lyot of the Pic du Midi Observatory and at the Haute Provence Observatory, both operated by the Institut des Sciences de l'Univers of the CNRS

Send offprint requests to: G. Vauclair

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© European Southern Observatory (ESO) 2000

Online publication: March 17, 2000
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