Possible association of a quiescent x-ray source with a gamma-ray burster

We report on the first repeatedly detected statistically significant coincidence (chance probability approximate to 10(-2)-10(-3)) between an X-ray source and a gamma-ray burst error box. We present three ROSAT observations of the field of the gamma-ray burst of 1992 May 1. The first, a 2000 s target of opportunity observation, was carried out 18 days after the burst. A weak X-ray source was identified, but with too few photons to determine its spectral characteristics. The second, a 30 ks PSPC observation, resulted in the detection of 118 net photons over the 0.07-2.4 keV energy range. We find that the spectrum is consistent with thermal bremsstrahlung from a 7 x 10(6) K plasma with about 10(22) cm(-2) H I column density. The unabsorbed flux is similar to 9.4 x 10(-13) ergs cm(-2) s(-1) (corresponding absorbed flux 4.8 x 10(-14) ergs cm(-2) s(-1)). Analysis of the photon arrival times indicates that the source may be variable. Using the H I column density from the spectral fit, we set a lower limit to the source distance of at least several kpc; an extragalactic source cannot be ruled out. If the gamma-ray burst is indeed belated to the X-ray source, its total energy output would have been at least 2 x 10(37) ergs. The third observation, 6200 s with the HRI, defines a source error circle of 6'' radius. We discuss optical observations of this region, and consider various possibilities for the nature of the X-ray source.