[vsnet-grb-info 27034] GRB 201216A - further Swift-XRT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29137
SUBJECT: GRB 201216A - further Swift-XRT observations
DATE:    20/12/22 16:55:43 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

P.A. Evans (U. Leicester), A. Tohuvavohu (U Toronto), J.A. Kennea (PSU) and T.
Sbarrato (INAF-OAB) report on behalf of the Swift-XRT team.

Swift has reobserved the field of GRB 201216A (GCN Circs. 29057, 29059) for a
further 4 ks, between 00:18 UT and 11:58 UT on 2020 December 22.

One of the sources in the XRT field of view appears to have faded (with 2.1
sigma significance). This source, “source 5” in the automated analysis
(https://www.swift.ac.uk/ToO_GRBs/00021408/) is located at RA,Dec = 201.45786,
+36.3944, which is equivalent to:

RA(J2000):  13h 25m 49.89s
Dec (J2000): +36d 23’ 39.8”

with an uncertainty of 3.0 arcsec (radius, 90% confidence). This position is 5.2
arcmin away from the BAT/GUANO position (Tohovavohu et al. GCN Circ. 29059),
well outside the 3 arcmin, 90% confidence BAT error region. It is also
coincident with a catalogued object in (among others) the USNO-B1, 2MASS, SDSS
and WISE catalogues, which NED classifies as a galaxy. 

We suggest therefore that this source is most likely simply a variable AGN near
(in projection) to GRB 201216A, but cannot rule out the possibility of it being
the GRB afterglow.

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