A White Dwarf Companion to the B5 V Star HR 2875 (y Puppis)
Vennes, Stéphane; Christian, Damian J.; Berghöfer, Thomas W.
United States, Australia
Abstract
An extreme-ultraviolet source in the EUVE and ROSAT Wide Field Camera catalogs, also identified with a very soft ROSAT PSPC X-ray source, is coincident with the B5 V star HR 2875 (y Pup). We present an analysis of PSPC and EUVE spectra revealing the presence of a hot white dwarf companion to HR 2875, which then constitute the first confirmed B star plus white dwarf system. The B star shows variable Si II, He I, and H I line profiles in high-dispersion spectra, possibly related to its binary nature, but our measurements limit the radial velocity semiamplitude of the B star to <=2 km s-1. We speculate that the white dwarf is most likely massive, and we propose some observational tests of the model.
Based on observations obtained at Lick Observatory, operated by the University of California, Mount Stromlo Observatory, operated by the Australian National University, and with ROSAT and NASA's Extreme Ultraviolet Explorer.