Two new ZZ Ceti pulsators from the HS and HE surveys

¹ INAF – Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy e-mail: silvotti@na.astro.it
² Institut für Theoretische Physik und Astrophysik der Universität Kiel, Leibnizstraße 15, 24098 Kiel, Germany e-mail: voss@astrophysik.uni-kiel.de,koester@astrophysik.uni-kiel.de
³ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: ivan.bruni@bo.astro.it
⁴ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany e-mail: dreimers@hs.uni-hamburg.de
⁵ Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK e-mail: r.napiwotzki@star.herts.ac.uk
⁶ Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany e-mail: derek@astro.physik.uni-goettingen.de

Received: 3 May 2005
Accepted: 9 June 2005

Abstract

We report the detection of nonradial g-mode oscillations in the DA white dwarfs HS 1039+4112 () and HE 1429-0343 () from time-series photometry made at the Loiano 1.5 m telescope. The two stars were previously selected as probable pulsators based on two-color photometry and spectral analysis respectively. Following our temperature and surface gravity determinations, HS 1039+4112 (T_eff K, ) is located near the red edge of the ZZ Ceti instability strip, whereas HE 1429-0343 (T_eff K, ) falls in the middle of the strip. Both stars show a multi-mode behavior with the main periods at about 850 and 970 s respectively, and relatively large amplitudes (~7% and ~2.5%).