Published by the University of Chicago Press for the Astronomical Society of the Pacific
Publications of the Astronomical Society of the Pacific vol:392 pages:301-308
Hot Subdwarf Stars and Related Objects edition:3 location:Bamberg date:23-27 July 2007
We present results from analysis of low-resolution time-series spectroscopy of Balloon 090100001, obtained with the Nordic Optical Telescope in August/September 2004. Variations in surface parameters for the four strongest pulsation periods are investigated by phase folding and fitting to model spectra. A detailed analysis of the dominant mode, together with modelling of the projection factors for a range of different modes, shows that only a radial mode is consistent with the observed velocity and gravity variations. We calculate a pulsational radius of 0.213 Rȯ, which corresponds to a total mass of 0.443 Mȯ for the observed mean surface gravity. We warn that these derivations are very sensitive to the accuracy of the radial velocity and gravity variation measurements.