GCN Circular 15173
Dirk Grupe (PSU) and Stephen Holland (STSCI) report on behalf of the Swift team: We have analysed 3.2 ks of XRT data for the INTEGRAL-detected burst: GRB 130903A, from 39.6 ks to 46.4 ks after the INTEGRAL trigger. The data are entirely in Photon Counting (PC) mode. An X-ray source is detected within the INTEGRAL error circle (Mereghetti et al., GCN circ. 15169). Using 1789 s of PC mode data and 1 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 82.13013, -0.12667 which is equivalent to: RA (J2000): 05h 28m 31.23s Dec(J2000): -00d 07' 36.0" with an uncertainty of 4.3 arcsec (radius, 90% confidence). This position is 12 arcsec from the INTEGRAL position. Currently the source has a 0.3-10 keV count rate in the Swift XRT of (4.9+4.9-3.0)e-3 counts/s. We cannot determine at the present time whether the source is fading. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020294. The Swift UVOT observed the field of GRB 130903A in V and U for 2462 and 780s, respectively. No optical counterpart was found. The 3-sigma upper limits at the position of the X-ray source are 20.6 in V and 20.4 in U. This circular is an official product of the Swift team.