EDP Sciences
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Volume 386, Number 1, April IV 2002
Page(s) 249 - 255
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20020200

A&A 386, 249-255 (2002)
DOI: 10.1051/0004-6361:20020200

HS0702+6043 - A new large amplitude sdB variable at the cool end of the instability region

S. Dreizler1, S. L. Schuh1, J. L. Deetjen1, H. Edelmann2 and U. Heber2

1  Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
    e-mail: schuh@, deetjen@astro.uni-tuebingen.de
2  Dr.-Remeis-Sternwarte, Universität Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany
    e-mail: heber@, edelmann@sternwarte.uni-erlangen.de

(Received 15 October 2001 / Accepted 4 February 2002 )

We report on time series photometry of hot sdB stars from the Hamburg Schmidt survey carried out at the Calar Alto 1.23 m and 2.2 m telescopes. Among 14 spectroscopically selected candidates we detected oscillations in the sdB star HS0702+6043 with a period of 363 s and an amplitude of 29 mmag which is among the largest amplitude observed in sdBV stars. A second period of 382 s with a significantly smaller amplitude (3.8 mmag) might be present. Our NLTE model atmosphere analysis of the time-averaged optical spectra, obtained at the Calar Alto 3.5 m telescope, indicates that HS0702+6043 has $T_{\rm eff}=28\,400$ K and $\log\,g=5.35$. This places the star at the cool end of the theoretical sdBV instability strip (EC 14026 stars). Among the other thirteen sdB stars we confirmed the variablity of the previously discovered sdBV HS0815+4243 and identified twelve stars to be stable, for which we give upper limits for light variations.

Key words: stars: subdwarfs -- stars: oscillations -- stars: individual: HS0702+6043 -- stars: fundamental parameters -- stars: horizontal branch

Offprint request: S. Dreizler, dreizler@astro.uni-tuebingen.de

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© ESO 2002