The photospheric temperature and metal abundance of the compact star H 1504+65.

Abstract

A new analysis of an Exosat low-energy telescope observation of the hot compact star H1504 + 65 is presented. Earlier results had failed to take into account the large point-spread function produced by the boron filter, and hence the count rate had been underestimated by a large factor. On comparing the data with a new grid of model atmospheres containing CNO metals, the temperature, line-of-sight column density, and photospheric elemental abundances for the star were estimated. Contrary to earlier suggestions it appears that H1504 + 65 is not devoid of He and may also have significant H present in its photosphere. These results are consistent with H1504 + 65 being the hottest member of the PG1159 - 035 spectroscopic group of degenerate stars and not a peculiar individual star.