A new slowly pulsating subdwarf-B star: HD 4539

Abstract

We report the spectroscopic discovery of slow pulsations in the subdwarf-B (sdB) star HD 4539. It is amongst the brightest sdB stars and, as such, has been well studied. Its temperature and gravity would place it squarely where the so-called “Betsy” stars (long-period sdB pulsators) are found, and this has been confirmed by the discovery of line-profile variations reported in this paper for the first time. As periodogram analyses of radial velocity curves obtained in 2005 and 2006 yield several significant frequencies, line-profile variations are very probably a consequence of pulsation.