GCN Circular 17977
Paul Kuin (MSSL-UCL), Marissa McCauley (PSU) and Daniele Malesani (DARK/NBI) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of the Fermi GRB 150627A 33622 s after the LAT trigger (Arimoto et al., GCN Circ. 17971; Yu et al., GCN Circ. 17975). An optical object consistent with the XRT position (Gompertz et al., GCN Circ. 17976) is detected at RA, Dec = 117.47108, -51.489417 deg (J2000), which is equivalent to: RA (J2000): 07:49:53.06 Dec(J2000): -51:29:21.9 with an uncertainty of 1". Preliminary detections 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 white 33963 34289 335 19.11+/-0.10 white 39860 40112 248 19.55+/-0.17 white 45659 45863 204 19.28+/-0.14 v 34304 34601 298 19.02+/-0.32 v 40117 40346 225 18.98+/-0.36 u 33622 38243 577 18.90+/-0.10 u 43668 45654 966 19.00+/-0.11 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.32 in the direction of the burst (Schlegel et al. 1998). While no optical variability can be securely inferred from the UVOT photometry, the source is not visible in the DSS survey, and brighter than its limit, which suggests it to be the optical afterglow of GRB 150627A.