2 X-ray sources

The WFC error box contains two X-ray sources (Pian et al. 1998a,b), one of which coincides with SN1998bw (Piro et al. 1998). The other one, 1SAXJ1935.3 - 5252, was detected at $(1.6 \pm 0.3) \ 10^{-13}$ erg cm^-2s^-1 about 1 day after the burst, and was marginally detected 6 days after the burst ($< 1.0 \ 10^{-13}$ erg cm^-2s^-1). This behavior is inconsistent with that of previously observed X-ray afterglows of GRBs, although it could be reconciled with it under some assumption (see the contribution to these proceedings by Pian et al.).

The 2-10 keV detection limit ($3\sigma$) for the GRB980425 Narrow-Field Instrument observations was $1.2 \ 10^{-13}$ erg s^-1 cm^-2. Using the ASCA 2-10 keV source count distributions (Cagnoni et al. 1998) one expects to find an average of 0.6 X-ray sources above this limit in the WFC error box; the probability of finding two or more sources there by chance coincidence is 12%. The case for a relation between this X-ray source and GRB980425 must therefore be considered tentative at best, in particular since among weak ROSAT sources variability is not rare.