Physical properties of the pulsating hydrogen - de cient starLSS

We report new determinations of the radius and mass of the pulsating helium-rich, hydrogen-deecient star LSS 3184 (BX Cir) using measurements of radial velocity and angular radius throughout its pulsation cycle. Measurements of radial velocity, and thus changes in stellar radius ((R ?), were made using Anglo-Australian Telescope echelle spectra. Hubble Space Telescope ultraviolet spectra and ground-based BV photometry were used to nd temperatures and uxes throughout the pulsation cycle. The temperatures and uxes were used to nd the angular radius of the star (). The , , and R values thus found were used to calculate the mean stellar radius hR ? i = 2:310:10R. If we use the previously determined log g = 3:35 0:1 for LSS 3184 and our radius estimate, we nd its mass to be M ? = 0:42 0:12M .