Persistent X-ray emission from a #betta#-ray burst source

A quiescent X-ray source, detected with the Einstein X-ray Observatory in a location consistent with that of an intense #betta#-ray burst, is shown to be also consistent with the location of the 1928 optical transient, the likely optical counterpart of the #betta#-ray burst source GBS0117-29. The probable maximum X-ray luminosity is only of the order of 1031 erg s-1 and supports the hypothesis that either #betta# bursts are produced by accretion instabilities or, if due to published models for a thermonuclear flash, they recur with intervals > approx. 50 yr. Such log recurrence times may be inconsistent with limits inferred from both the #betta# burst observation and optical data. (author)