TITLE: GCN CIRCULAR NUMBER: 42417 SUBJECT: GRB 251022A: Swift-XRT detection of GOTO25iym DATE: 25/10/24 08:12:16 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 251022A in a series of observations tiled on the sky. The total exposure time is 4.6 ks, distributed over 4 tiles; the maximum exposure at a single sky location in the tiling was 2.5 ks. The data were collected between T0+26.7 ks and T0+71.7 ks, and are entirely in Photon Counting (PC) mode.
Seven uncatalogued X-ray sources have been detected, however none of them is above the RASS limit or shows definitive signs of fading in the X-rays.
Source 4 is 2.6 arcsec from the reported optical transient GOTO25iym (O'Neill et al., GCN Circ. 42386) and thus is likely the counterpart to that transient and the GRB afterglow, though we cannot at present confirm fading in X-rays. The details of this source are:
Source 4: RA (J2000.0): 65.4968 = 04h 21m 59.23s Dec (J2000.0): -18.9188 = -18d 55' 07.8" Error: 4.8 arcsec (radius, 90% conf.) Count-rate: 0.0110 [+0.0026, -0.0025] ct s^-1 Distance: 1463 arcsec from Fermi/LAT position. Flux: (2.96 [+0.71, -0.67])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
The other 6 uncatalogued sources detected are enumerated below:
Source 1: RA (J2000.0): 65.0135 = 04h 20m 03.25s Dec (J2000.0): -19.3306 = -19d 19' 50.1" Error: 6.3 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: 0.0173 [+0.0061, -0.0050] ct s^-1 Distance: 1247 arcsec from Fermi/LAT position. Flux: (3.5 [+1.2, -1.0])e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Source 2: RA (J2000.0): 65.0984 = 04h 20m 23.62s Dec (J2000.0): -19.2625 = -19d 15' 45.2" Error: 5.4 arcsec (radius, 90% conf.) Count-rate: 0.0115 [+0.0046, -0.0037] ct s^-1 Distance: 971 arcsec from Fermi/LAT position. Flux: (4.4 [+1.8, -1.4])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Source 5: RA (J2000.0): 65.3796 = 04h 21m 31.10s Dec (J2000.0): -18.9857 = -18d 59' 08.4" Error: 6.0 arcsec (radius, 90% conf.) Count-rate: (7.7 [+2.6, -2.1])e-3 ct s^-1 Distance: 1167 arcsec from Fermi/LAT position. Flux: (2.17 [+0.72, -0.60])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Source 6: RA (J2000.0): 65.5456 = 04h 22m 10.93s Dec (J2000.0): -19.1086 = -19d 06' 30.8" Error: 6.5 arcsec (radius, 90% conf.) Count-rate: (6.0 [+2.5, -2.0])e-3 ct s^-1 Distance: 917 arcsec from Fermi/LAT position. Flux: (9.1 [+3.9, -3.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Source 8: RA (J2000.0): 65.4382 = 04h 21m 45.16s Dec (J2000.0): -19.0268 = -19d 01' 36.6" Error: 7.8 arcsec (radius, 90% conf.) Count-rate: (3.2 [+1.8, -1.3])e-3 ct s^-1 Distance: 1038 arcsec from Fermi/LAT position. Flux: (6.8 [+3.9, -2.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Source 9: RA (J2000.0): 65.3956 = 04h 21m 34.95s Dec (J2000.0): -19.0576 = -19d 03' 27.4" Error: 6.3 arcsec (radius, 90% conf.) Count-rate: (3.6 [+2.1, -1.5])e-3 ct s^-1 Distance: 910 arcsec from Fermi/LAT position. Flux: (1.15 [+0.65, -0.48])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Two catalogued sources were also detected.
The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00139.
This circular is an official product of the Swift-XRT team.
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