TITLE: GCN CIRCULAR NUMBER: 35064 SUBJECT: GRB 231115A: Swift-XRT and Swift-UVOT observations DATE: 23/11/16 14:39:58 GMT FROM: Phil Evans at U of Leicester J.P. Osborne (U. Leicester), B. Sbarufatti (INAF-OAB), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), J. D. Gropp (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) and S. R. Oates (Lancaster U.) report on behalf of the Swift-XRT and the Swift-UVOT teams: Swift-XRT has performed follow-up observations of the INTEGRAL-detected burst GRB 231115A, which is likely not a GRB, but it is likely a MGF (Burns GCN Circular 35038) and whose position is consistent with M82 galaxy (D'Avanzo et al. GCN Circ. 35036; Mereghetti et al. GCN Circ. 35037), collecting 4.4 ks of Photon Counting (PC) mode data between T0+9.0 ks and T0+39.2 ks. No uncatalogued X-ray sources have been detected consistent with being within 303 arcsec of the INTEGRAL position. The 3-sigma upper limit in the field ranges from ~0.002 to ~0.003 ct s^-1, corresponding to a 0.3-10 keV observed flux of 8.2e-14 to 1.2e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum). Six previously-catalogued X-ray sources have been detected consistent with being within 303 arcsec of the INTEGRAL position, however their status as catalogued objects makes them unlikely to be the X-ray counterpart. An uncatalogued object was detected, however this was too far from the GRB position to be the X-ray counterpart. We note that the diffuse X-ray emission from the M82 galaxy affects a significant fraction of the INTEGRAL error circle. This likely reduces the sensitivity for source detection. The results of the XRT-team automatic analysis of the XRT observations, including a position specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021625. No optical counterpart consistent with the INTEGRAL position (Mereghetti et al., GCN Circ. 35037) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are: Filter T_start(s) T_stop(s) Exp(s) Mag w1 9253 39224 4283 >17.4 The magnitude in the table is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.155 in the direction of the burst (Schlegel et al. 1998). This circular is an official product of the Swift team.