GCN Circular 33789

J.P. Osborne (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato
(INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), A. Tohuvavohu
(U. Toronto), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester) 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 230512A in a series of observations tiled
on the sky. The total exposure time is 4.9 ks, distributed over 4
tiles; the maximum exposure at a single sky location was 2.3 ks. The
data were collected between T0+45.5 ks and T0+57.3 ks, and are entirely
in Photon Counting (PC) mode. 

Nine 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):  295.4803  =  19:41:55.26
  Dec (J2000.0): +38.6649  =  +38:39:53.6
  Error: 4.2 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (8.8 [+3.9, -3.0])e-3 ct s^-1   
  Distance: 980 arcsec from Fermi/LAT position.
  Flux: (5.1 [+2.2, -1.8])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:
  RA (J2000.0):  295.5430  =  19:42:10.33
  Dec (J2000.0): +38.7526  =  +38:45:09.4
  Error: 5.5 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: 0.0176 [+0.0056, -0.0047] ct s^-1   
  Distance: 1331 arcsec from Fermi/LAT position.
  Flux: (3.57 [+1.13, -0.95])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 5:
  RA (J2000.0):  295.2060  =  19:40:49.43
  Dec (J2000.0): +38.4686  =  +38:28:07.1
  Error: 6.2 arcsec (radius, 90% conf.)
  Count-rate: 0.0105 [+0.0042, -0.0034] ct s^-1   
  Distance: 600 arcsec from Fermi/LAT position.

Source 6:
  RA (J2000.0):  295.7616  =  19:43:2.79
  Dec (J2000.0): +38.3644  =  +38:21:51.9
  Error: 3.9 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (6.7 [+3.5, -2.6])e-3 ct s^-1   
  Distance: 1028 arcsec from Fermi/LAT position.

Source 7:
  RA (J2000.0):  295.0895  =  19:40:21.48
  Dec (J2000.0): +38.4348  =  +38:26:05.5
  Error: 6.8 arcsec (radius, 90% conf.)
  Count-rate: (5.4 [+3.3, -2.4])e-3 ct s^-1   
  Distance: 884 arcsec from Fermi/LAT position.

Source 8:
  RA (J2000.0):  295.3130  =  19:41:15.11
  Dec (J2000.0): +38.4565  =  +38:27:23.3
  Error: 5.1 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (8.7 [+4.1, -3.2])e-3 ct s^-1   
  Distance: 318 arcsec from Fermi/LAT position.

Source 9:
  RA (J2000.0):  295.2484  =  19:40:59.62
  Dec (J2000.0): +38.1016  =  +38:06:05.7
  Error: 7.7 arcsec (radius, 90% conf.)
  Count-rate: (5.5 [+3.1, -2.3])e-3 ct s^-1   
  Distance: 1156 arcsec from Fermi/LAT position.

Source 10:
  RA (J2000.0):  295.1589  =  19:40:38.13
  Dec (J2000.0): +38.4685  =  +38:28:06.6
  Error: 6.1 arcsec (radius, 90% conf.)
  Count-rate: (9.8 [+5.8, -4.3])e-3 ct s^-1   
  Distance: 723 arcsec from Fermi/LAT position.

Source 11:
  RA (J2000.0):  295.2125  =  19:40:50.99
  Dec (J2000.0): +38.0868  =  +38:05:12.5
  Error: 4.5 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (9.5 [+4.1, -3.2])e-3 ct s^-1   
  Distance: 1245 arcsec from Fermi/LAT position.
  Flux: (3.3 [+1.4, -1.1])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_GRB00111.

This circular is an official product of the Swift-XRT team.