The pulsating extreme helium star BD +13 3224. II. Ultraviolet fluxesand effective temperature variations.
Heber, U.; Lynas-Gray, A. E.; Hill, P. W.; Schoenberner, D.
United Kingdom, Germany, United States, Australia
Abstract
BD + 13 deg 3224 (V652 Her) is characterized on the basis of low-resolution spectra obtained with the short-wavelength prime camera of the IUE on July 5, 1980, and optical spectra obtained at integration time 200 s with the 3.9-m Anglo-Australian Telescope on May 24 and 25, 1980. The results are presented in tables and graphs and discussed. Static plane-parallel LTE model atmospheres are used to calculate effective temperature and angular radius variations over a cycle of UV-flux variation. It is estimated that the star has mass 0.7 solar mass and lies at a distance of 1.5 + or - 0.1 kpc. It exhibits radial pulsations and has an envelope which contracts as the He-burning core grows; thus it resembles H-deficient star HD 144941.