A. Ahmad1*, C. S. Jeffery1C.
Aerts2,3 , G.
Fontaine4 and S. Charpinet5
1 Armagh Observatory, Col lege Hil l, Armagh BT61 9DG, N. Ireland
2 Inst. of Astronomy, Catholic Univ. of Leuven, Celestijnenlaan 200 D, Leuven, Belgium
3 Dept. of Astrophysics, Radboud Univ. Nijmegen, PO Box 9010, Nijmegen, the Netherlands
4 Department de Physique, Universite de Montreal, C.P. 6128, Quebec, Canada H3C 3J7
5 Universitat Paul Sabbatier et CNRS, Observatoire Midi-Pyrenees, Toulouse, France
Abstract. About one tenth of all hot subluminous B stars pulsate non- radially with periods of 80 - 600 s; the oscillations are identified with pressure modes. At lower effective temperatures, another group pulsates non-radially with periods > 3 000 s; these oscillations have been identified with gravity modes. If sufficient modes can be identified, such oscillations can provide infor- mation about the interior of a star. One pulsating sdB star - balloon 090100001 - lies at the boundary of the hot and cool groups, and shows both short and long-period oscillations. To study its interior structure in detail, we carried out a multi-site observing campaign in 2005 August in order to obtain a very pre- cise light curve and hence to identify the modes of oscillation. This campaign involved four telescopes including the Himalayan Chandra Telescope (HCT), the William Herschel Telescope (in La Palma), the Canada France Hawaii Tele- scope and the Faulkes Telescope North (both in Hawaii). Here we report the HCT observations of balloon 090100001.
Keywords : stars: individual: balloon 090100001 - subdwarfs - stars: oscillations - methods: observational-techniques: photometric
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