TITLE: GCN CIRCULAR NUMBER: 23031 SUBJECT: GRB 180718B: Swift-XRT observations DATE: 18/07/24 14:21:22 GMT FROM: Boris Sbarufatti at PSU B. Sbarufatti (INAF-OAB/PSU), A. A. Breeveld (UCL-MSSL), Z. Liu (NAOC / U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows (PSU), A. Tohuvavohu (PSU) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 180718B (Crnogorcevic et al. GCN Circ. 22961), collecting 5.0 ks of Photon Counting (PC) mode data between T0+38.9 ks and T0+50.6 ks. Four uncatalogued X-ray sources have been detected, however none of them is above the RASS limit or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. The UVOT finds no new optical sources at the position of any of the four X-ray sources. Details of these sources are given below: Source 1: RA (J2000.0): 44.7960 = 02:59:11.03 Dec (J2000.0): -31.6692 = -31:40:09.2 Error: 3.0 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (9.0 +/- 2.4)e-3 ct s^-1 Distance: 705 arcsec from Fermi/LAT position. Flux: (2.79 +/- 0.74)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 2: RA (J2000.0): 44.6153 = 02:58:27.68 Dec (J2000.0): -31.6555 = -31:39:19.9 Error: 6.1 arcsec (radius, 90% conf.) Count-rate: (1.91 [+0.92, -0.71])e-3 ct s^-1 Distance: 593 arcsec from Fermi/LAT position. Flux: (5.1 [+2.4, -1.9])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 3: RA (J2000.0): 44.7970 = 02:59:11.27 Dec (J2000.0): -31.4797 = -31:28:47.0 Error: 4.0 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (2.80 [+1.14, -0.91])e-3 ct s^-1 Distance: 366 arcsec from Fermi/LAT position. Flux: (1.19 [+0.49, -0.39])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 4: RA (J2000.0): 44.7053 = 02:58:49.28 Dec (J2000.0): -31.4407 = -31:26:26.5 Error: 5.0 arcsec (radius, 90% conf.) Count-rate: (2.51 [+1.10, -0.87])e-3 ct s^-1 Distance: 227 arcsec from Fermi/LAT position. Flux: (5.1 [+2.2, -1.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) 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/00020803. This circular is an official product of the Swift-XRT team.