The pulsating extreme helium star BD+13 3224 II. Ultraviolet fluxes and effective temperature variations

Ultraviolet flux variations are reported for the pulsating extreme helium star BD +13°3224 (V652 Her). Effective temperature and angular radius variations over a cycle are determined from static plane-parallel LTE model atmospheres. When compared with radius changes derived from ground-based spectroscopy, the angular radius variations indicate radial pulsations and correspond to a distance of 1.5±0.1 kpc. BD + 13°3224 is thought to be a helium-burning star of |0.7 M_|⁠, which has an envelope contracting as the helium-burning core grows; it is similar to HD 144941 and these two stars may constitute a new sub-class of the hydrogen-deficient stars.