Model for Centaurus X-3

Abstract

THE discovery of periodic variations in the X-ray flux from the source Cen X-3 (ref. 1) prompts us to reconsider the model of white dwarf pulsations which proved inadequate to explain the clock mechanism operating in pulsars. Faulkner and Gribbin have shown² that non-rotating white dwarf models obeying the Salpeter equation of state³ can be constructed with fundamental vibration periods as low as 2 s. In Cen X-3, the two periods reported are at 4.8 s and 2.4 s, so that although there is now some doubt concerning the validity of the Sal-peter equation of state at very high densities (W. A. Fowler, personal communication) the results given in ref. 2 will still be valid in the range of densities corresponding to models with fundamental periods of radial oscillation close to the longer period variation observed in Cen X-3. In particular, we note that, from ref. 2, the fundamental period of a model with central density (ρ_c) of 10⁸ g cm⁻³ is 4.49 s.