XTE J1739-302 - AN UNUSUAL NEW X-RAY TRANSIENT

A new X-ray transient, designated XTE J1739-302, was discovered with t he proportional counter array on the Rossi X-Ray Timing Explorer in da ta from 1997 August 12. Although it was the brightest source in the Ga lactic center region while active (about 3.0 x 10(-9) ergs cm(-2) s(-1 ) from 2 to 25 keV), it was only observed on that one day; it was not detectable 9 days earlier or 2 days later. There is no known counterpa rt at other wavelengths, and its proximity to the Galactic center will make such an identification difficult due to source confusion and ext inction. The X-ray spectrum and intensity suggest a giant outburst of a Be/neutron star binary, although no pulsations were observed and the outburst was shorter than is usual from these systems.