Extreme variability in the Be-type, periodic recurrent X-ray transient AO538-66 : a highly eccentric interacting binary.
Howarth, I. D.; Charles, P. A.; Willis, A. J.; Bath, G. T.; Thorstensen, J. R.; Skinner, G. K.; Booth, L.; Densham, R. H.; Olszewski, E.
United Kingdom
Abstract
The recurrent X-ray transient sources represent a substantial class of galactic objects which are difficult to study extensively. They can be divided into two groups on the basis of their optical primaries, including the low-mass systems which are optically faint outside their outbursts, and those with high masses. White and Carpenter (1978) discovered the periodic recurrent transient X-ray source A0538-66. The present investigation is concerned with an eccentric binary model of A0538-66, in which the neutron star is effectively imbedded in the primary's extended atmosphere at periastron. It is suggested that X-ray emission outside periastron is due to accretion from gravitationally bound gas, perhaps in the form of a disk around the compact object obtained during the previous periastron passage.