[vsnet-grb-info 21137] GRB 180914B: Swift-XRT afterglow detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23236
SUBJECT: GRB 180914B: Swift-XRT afterglow detection
DATE:    18/09/15 22:21:41 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <paolo.davanzo at brera.inaf.it>

A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), S. J. LaPorte (PSU),
J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), S.L. Gibson (U.
Leicester), Z. Liu (NAOC / U. Leicester), J.P. Osborne (U. Leicester),
P. D'Avanzo (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
Fermi/LAT-detected burst GRB 180914B (Bissaldi et al. GCN Circ. 23232)
in a series of observations tiled on the sky. The total exposure time
is 4.1 ks, distributed over 6 tiles; the maximum exposure at a single
sky location was 1.3 ks. The data were collected between T0+82.8 ks and
T0+93.8 ks, and are entirely in Photon Counting (PC) mode. 

An uncatalogued X-ray source is detected and is above the RASS limit,
and is therefore likely the GRB afterglow. Using 579 s of PC mode data
and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT
alignment and matching UVOT field sources to the USNO-B1 catalogue):
RA, Dec = 332.35648, +25.06314 which is equivalent to:

RA (J2000): 22h 09m 25.56s
Dec(J2000): +25d 03' 47.3"

with an uncertainty of 3.4 arcsec (radius, 90% confidence). This
position is 12.1 arcmin from the Fermi/LAT position.  The source has a
mean count rate of 6.2e-02 ct/sec; we cannot determine at the present
time whether it is fading.

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/xrt_products/TILED_GRB00075/Source2.php.
The results of the full analysis of the tiled XRT observations are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00075.

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