TITLE: GCN CIRCULAR NUMBER: 31749 SUBJECT: GRB 220310C: Swift-XRT observations DATE: 22/03/12 22:45:55 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), J. D. Gropp (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), J.A. Kennea (PSU) 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-GUANO-detected burst GRB 220310C, collecting 4.6 ks of Photon Counting (PC) mode data between T0+102.8 ks and T0+120.2 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. Details of these sources are given below: Source 1: RA (J2000.0): 289.9580 = 19:19:49.91 Dec (J2000.0): +40.2093 = +40:12:33.3 Error: 7.9 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (4.4 +/- 1.2)e-3 ct s^-1 Distance: 344 arcsec from Swift/BAT-GUANO position. Flux: (9.6 +/- 2.7)e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 2: RA (J2000.0): 290.2354 = 19:20:56.50 Dec (J2000.0): +40.3333 = +40:19:59.9 Error: 7.6 arcsec (radius, 90% conf.) Count-rate: (3.7 [+1.4, -1.1])e-3 ct s^-1 Distance: 539 arcsec from Swift/BAT-GUANO position. Flux: (1.39 [+0.51, -0.42])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 3: RA (J2000.0): 290.1544 = 19:20:37.05 Dec (J2000.0): +40.2064 = +40:12:23.0 Error: 6.3 arcsec (radius, 90% conf.) Count-rate: (1.92 [+0.98, -0.76])e-3 ct s^-1 Distance: 288 arcsec from Swift/BAT-GUANO position. Flux: (4.2 [+2.2, -1.7])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 4: RA (J2000.0): 289.8727 = 19:19:29.46 Dec (J2000.0): +40.2572 = +40:15:26.0 Error: 6.4 arcsec (radius, 90% conf.) Count-rate: (1.41 [+0.96, -0.69])e-3 ct s^-1 Distance: 540 arcsec from Swift/BAT-GUANO position. 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/00021483. This circular is an official product of the Swift-XRT team.