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Institut für Astronomie und Astrophysik

Abteilung Astronomie

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Preprint 15/02

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

Dreizler, S. (1); Schuh, S.L. (1); Deetjen, J.L. (1); Edelmann, H. (2); Heber, U.(2)

(1) Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Dr.-Remeis-Sternwarte, Universität Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany

Astronomy & Astrophysics, 386, 249-255 (2002)

Abstract. 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 Teff=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. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy.

Key words: Stars: Subdwarfs, Stars: Oscillations, Stars: Individual: HS0702+6043

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