Photometry of balloon 090100001 with the Himalayan Chandra Telescope

Abstract

About one tenth of all hot subluminous B stars pulsate non-radially with periods of 80 -- 600s; 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 information 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 precise 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 Telescope and the Faulkes Telescope North (both in Hawaii). Here we report the HCT observations of balloon 090100001.