An X-ray survey of beta Cephei stars

Abstract

Results of an X-ray survey of Beta Cephei stars are reported. Three of the six surveyed Beta Cephei stars are detected with an X-ray luminosity (L_X) lying in the range (0.8-4.2)×10³¹ erg s⁻¹. The mean value of the ratio of X-ray luminosity to bolometric luminosity (L_X/L_bol) for the Beta Cephei stars, including three from an earlier survey, is found to be 8.6×10⁻⁸. No dependence of L_X or L_X/L_bol is found on the binary or short pulsation periods of the observed stars. Likewise no correlation was found between L_X and the rotation velocity of the Beta Cephei stars. It is concluded that X-ray characteristics of Beta Cephei stars are indistinguishable from other B stars of similar luminosity class. There is an indication of X-ray flux variations by a factor of ≡2 on a time-scale of about 10 min from β CMa. Implications of the results are briefly discussed in terms of models of X-ray emission from early type stars.