GCN Circular 31342

V. D'Elia (SSDC & INAF-OAR), S. R. Oates (U.Birmingham), A. D'Ai
(INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N.
Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
A. Melandri (INAF-OAB) 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 211229A (Tohuvavohu et al., GCN
Circ. 31334
Not found
 
 
), also detected by Fermi/GBM and GECAM  (Fermi GBM team,
GCN Circ. 31329
Not found
 
 
, Zhao et al., GCN Circ. 31331
Not found
 
 
), collecting 5.0 ks of
Photon Counting (PC) mode data between T0+43.6 ks and T0+66.8 ks. 

Four uncatalogued X-ray sources have been detected consistent with
being within 394 arcsec of the Swift/BAT-GUANO position, 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):  295.1317  =  19:40:31.60
  Dec (J2000.0): +23.1983  =  +23:11:53.8
  Error: 6.3 arcsec (radius, 90% conf.)
  Count-rate: (3.5 [+1.3, -1.0])e-3 ct s^-1   
  Distance: 252 arcsec from Swift/BAT-GUANO position.
  Flux: (2.78 [+1.01, -0.83])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)


Source 2:
  RA (J2000.0):  295.0615  =  19:40:14.76
  Dec (J2000.0): +23.2617  =  +23:15:42.0
  Error: 9.7 arcsec (radius, 90% conf.)
  Count-rate: (1.60 [+0.88, -0.66])e-3 ct s^-1	 
  Distance: 398 arcsec from Swift/BAT-GUANO position.

Source 5:
  RA (J2000.0):  295.0738  =  19:40:17.70
  Dec (J2000.0): +23.1573  =  +23:09:26.3
  Error: 6.6 arcsec (radius, 90% conf.)
  Count-rate: (2.12 [+0.97, -0.76])e-3 ct s^-1	 
  Distance: 20 arcsec from Swift/BAT-GUANO position.
  Flux: (1.59 [+0.72, -0.57])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)


Source 6:
  RA (J2000.0):  295.1187  =  19:40:28.49
  Dec (J2000.0): +23.1638  =  +23:09:49.7
  Error: 5.3 arcsec (radius, 90% conf.)
  Count-rate: (2.94 [+1.13, -0.91])e-3 ct s^-1	 
  Distance: 151 arcsec from Swift/BAT-GUANO position.

An uncatalogued source was also detected, however this was too far from
the GRB position to be the afterglow.

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/00021475.

No optical afterglow consistent with the GUANO position
(Tohuvavohu et al., GCN Circ. 31334
Not found
 
 
)
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) for the initial
exposures are:

Filter	       T_start(s)   T_stop(s)	   Exp(s)	  Mag

u		 43722	      66830	      4882	   >21.0

The magnitudes in the table are not corrected for the Galactic
extinction
due to the reddening of E(B-V) = 5.811 in the direction of the burst
(Schlegel et al. 1998).

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