Whole Earth Telescope observations of the pulsating hot white dwarf PG 1707+427

¹ Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA e-mail: sdk@iastate.edu
² School of Physics, University of Sydney, Sydney NSW, Australia
³ Dr. Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstr. 7, Bamberg 96049, Germany
⁴ Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255, USA
⁵ Department of Astronomy, Yale University, New Haven, CT 06851, USA
⁶ Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204, USA
⁷ Department of Astronomy, University of Texas, Austin, TX 78712, USA
⁸ Nicolas Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
⁹ National Optical Astronomy Observatory, 950 N. Cherry Ave, Tucson, AZ 85719, USA
¹⁰ Département de Physique, Université de Montréal, Montréal, Québec, H3C 3J7, Canada
¹¹ Université Paul Sabatier, Observatoire Midi-Pyrénées, 14 avenue E. Belin, 31400 Toulouse, France
¹² Observatoire de Paris-Meudon, DAEC, 92195 Meudon, France
¹³ Apache Point Observatory, PO Box 59, Sunspot, NM 88349, USA
¹⁴ Southwestern University, 1001 E. University Avenue, Georgetown, TX 78626, USA
¹⁵ Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
¹⁶ Isaac Newton Group of Telescopes, 37800 Santa Cruz de La Palma, Canary Islands, Spain
¹⁷ Centre for Astrophysics, University of Central Lancashire, Preston, Lancashire, PR1 2HE, UK
¹⁸ Instituto de Física, UFRGS, Campus do Vale, CP 15051 Porto Alegre, RS, Brazil
¹⁹ Departamento de Física, Universidade Federal de Santa Catarina, CP 4796-CDP 88040-900 Florianópolis, SC-Brazil
²⁰ Los Alamos National Laboratory, X-2, MS T-085, Los Alamos, NM 87545, USA
²¹ Department of Physics and Astronomy, University of Delaware, 223 Sharp Laboratory, Newark, DE 19716, USA

Received: 15 June 2004
Accepted: 27 August 2004

Abstract

We report on the analysis of multisite time-series photometry of the pulsating pre-white dwarf (GW Vir star) PG 1707+427, obtained by the Whole Earth Telescope collaboration. This is the last of the known GW Vir stars without surrounding nebulae to be resolved by multisite data. Successful resolution of the pulsation spectrum resulted from the combination of high signal-to-noise observations with a large telescope and wide coverage in longitude with smaller telescopes. We find a series of 8 pulsation frequencies (along with two nonlinear combination frequencies), and identify 7 of them as part of a sequence of  modes, with a common period spacing of 23.0 s. This spacing implies that the mass of PG 1707+427 is . Preliminary model fits suggest that the mass determined via asteroseismology is consistent with the mass determined from spectroscopy combined with evolutionary tracks.