TITLE: GCN CIRCULAR NUMBER: 14287 SUBJECT: GRB 130306A: Swift Detection of a Possible Afterglow DATE: 13/03/11 15:07:32 GMT FROM: Mike Siegel at PSU/Swift MOC GRB 130306A: Swift Detection of a Possible Afterglow M. H. Siegel (PSU), David N. Burrows (PSU) and Dirk Grupe (PSU) report on behalf of the Swift team: On 8 March 2013 the Swift spacecraft performed a delayed observation of the BAT-detected burst GRB 130306A (Siegel et al., GCN 14266), which was also detected by Fermi GBM (Pelassa, GCN 14270) and Konus/Wind (Golenetskii et al., GCN 14275). We have analyzed 5.1 ks of XRT data, from 146 to 163 ks after the Swift/BAT trigger. The data are entirely in photon counting (PC) mode. An X-ray source is detected within the Swift/BAT error circle. The XRT position is RA, Dec = 279.46147, -11.68123 which is equivalent to: RA (J2000) = 18 37 50.75 Dec(J2000) = -11 40 52.4 with an uncertainty of 4.0 arcsec (radius, 90% confidence). We do not detect any fading over the time span of the Swift observations. The Swift/UVOT began settled observations of the field of GRB 130306A 146 ks after the Swift/BAT trigger. No optical afterglow consistent with the XRT position is detected in the initial UVOT exposures. Preliminary 3-sigma upper limit using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag uvw1 145609 162770 4707 >22.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.15 in the direction of the burst (Schlegel et al. 1998). Further observations are planned to determine if the source is fading.