Institutt for Fysikk, Universitetet i Tromsø, 9037 Tromsø, Norway e-mail: firstname.lastname@example.org
2 Dr. Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, 96049 Bamberg, Germany e-mail: email@example.com; firstname.lastname@example.org
3 Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy e-mail: email@example.com
4 Institut für Astronomie und Astrophysik, Waldhäuser Straße 64, 72076 Tübingen, Germany e-mail: firstname.lastname@example.org
Corresponding author: R. Østensen, email@example.com
Accepted: 5 December 2000
We report the detection of short period oscillations in the sdB stars HS 0815+4243, HS 2149+0847 and HS 2201+2610 from time-series photometry made at the Nordic Optical Telescope (NOT) from a sample of 31 candidates. Hence these three hot subdwarfs are new members of the EC 14026 class of pulsating sdB stars. One short period is detected for HS 0815+4243 (P ∼ 126 s; A ∼ 7 mma) and two short periods are seen for HS 2149+0847 (P ∼ 142, 159 s; A ∼ 11, 7 mma), whereas the single oscillation detected for HS 2201+2610 has a considerably longer period (P ∼ 350 s; A ∼ 11 mma). Our NLTE model atmosphere analysis of the time-averaged optical spectra indicate that HS 0815+4243 has Teff = 33 700 K and , HS 2149+0847 has K and log , and HS 2201+2610 has Teff = 29 300 K and log . This places the former two at the hot end and the latter at the cool end of the theoretical sdBV instability strip.
Key words: subdwarfs / stars: oscillations / stars: individual: HS 0815+4243 HS 2149+0847 HS 2201+2610
Based on observations obtained at the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.
© ESO, 2001