TITLE: GCN CIRCULAR NUMBER: 21318 SUBJECT: GRB 170710B: Swift-XRT and UVOT observations DATE: 17/07/11 14:52:33 GMT FROM: Phil Evans at U of Leicester K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Cholden-Brown (PSU), B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), A.A. Breeveld (MSSL/UCL), S.B. Cenko (GSFC) and P.A. Evans (U. Leicester) report on behalf of the Swift team: Swift has performed follow-up observations of the BAT and Fermi/GBM-detected burst GRB 170710B (Palmer & Lien, GCN Circ. 21316), collecting 4.0 ks of Photon Counting (PC) mode data between T0+85.2 ks and T0+92.7 ks. One uncatalogued X-ray source has been detected consistent with being within 296 arcsec of the BAT position; it is below the RASS limit and shows no definitive signs of fading. It is 4.8" from SDSS J025227.08+423819.4, which is a possible quasar, therefore more data are needed to confirm whether the XRT source is the GRB afterglow. Further observations are planned. Details of this source are given below: Source 1: RA (J2000.0): 43.1110 = 02:52:26.65 Dec (J2000.0): +42.6391 = +42:38:20.7 Error: 3.3 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (6.4 [+1.6, -1.4])e-3 ct s^-1 Distance: 146 arcsec from BAT position. Flux: (2.51 [+0.61, -0.56])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) The UVOT started observing this source 85.2 ks after the burst. The catalogued source just on the edge of the XRT region is detected, but no new source is found to an upper limit in the UVW2 filter of 21.3 mag in 3924s of exposure. Two uncatalogued X-ray sources were also detected too far from the GRB position to be likely afterglow candidates. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00020777. This circular is an official product of the Swift2 team.