GCN Circular 31411

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
Not found
 
 
)
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 https://www.swift.ac.uk/xrt_products/TILED_GRB00103/Source1.php.

The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00103.

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