TITLE: GCN CIRCULAR NUMBER: 18018 SUBJECT: GRB 150710B: Swift-XRT and Swift-UVOT observations DATE: 15/07/12 10:43:27 GMT FROM: Andrea Melandri at INAF-OAB A. Melandri (INAF-OAB), P. Kuin (MSSL-UCL), V. D'Elia (ASDC), A. D'ai (INAF-IASFPA), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), A. Maselli (INAF-IASFPA) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Swift/BAT-detected burst GRB 150710B (Cummings et al. GCN Circ. 18009), collecting 2.8 ks of Photon Counting (PC) mode data between T0+115.2 ks and T0+121.6 ks. An uncatalogued X-ray source has been detected close to the refined Swift/BAT error region (Cummings et al. GCN Circ. 18013), it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: RA (J2000.0): 83.2176 = 05:32:52.23 Dec (J2000.0): -46.9423 = -46:56:32.4 Error: 4.7 arcsec (radius, 90% conf.) Count-rate: 0.0141 [+0.0031, -0.0027] ct s^-1 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/00020542. Simultaneous with the Swift-XRT, the Swift-UVOT observed the field of GRB 150710B. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 115375 120586 662 >21.1 v 115594 121561 957 >19.5 u 115157 120072 915 >20.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998). This circular is an official product of the Swift-XRT team.