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GCN Circular 31411

GRB 220107B: Swift-XRT afterglow detection
2022-01-08T09:33:21Z (2 years ago)
Phil Evans at U of Leicester <>
J. D. Gropp (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester),
J.P. Osborne (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo
(INAF-OAB), M.G. Bernardini (INAF-OAB), A. Tohuvavohu (U. Toronto) 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 220107B (Arimoto et al. GCN Circ. 31409)
in a series of observations tiled on the sky. The total exposure time
is 1.3 ks, distributed over 2 tiles; the maximum exposure at a single
sky location was 1.0 ks. The data were collected between T0+35.7 ks and
T0+36.2 ks, and are entirely in Photon Counting (PC) mode. 

An uncatalogued X-ray source is detected and is above the RASS 3-sigma
upper limit at this position, and is therefore likely the GRB
afterglow. Using 546 s of PC mode data and 1 UVOT image, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 216.40652, +20.17064
which is equivalent to:

RA (J2000): 14h 25m 37.56s
Dec(J2000): +20d 10' 14.3"

with an uncertainty of 3.4 arcsec (radius, 90% confidence). This
position is 11.5 arcmin from the Fermi/LAT position.  The source has a
mean count rate of 1.3e-01 ct/sec; while we cannot determine at the
present time whether it is fading, the fact that the source is well
above RASS limit strongly suggests it is the X-ray afterglow of GRB
220107B. More data are currently being collected.

The results of the XRT-team automatic analysis of the likely afterglow
are at

The results of the full analysis of the tiled XRT observations are
available at

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