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GCN Circular 32874

GRB 221028A: Swift detection of a burst
2022-10-28T13:32:46Z (2 years ago)
Jamie Kennea at Penn State U <>
A. Y. Lien (U Tampa), E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU),
P. A. Evans (U Leicester), R. A. J. Eyles-Ferris (U Leicester),
J.D. Gropp (PSU), J. A. Kennea (PSU), S. Laha (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), M. J. Moss (GWU),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. M. Parsotan (GSFC/UMBC/CRESSTII), B. Sbarufatti (INAF-OAB),
M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 13:16:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 221028A (trigger=1131910).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 314.206, +41.066 which is 
   RA(J2000) = 20h 56m 49s
   Dec(J2000) = +41d 03' 56"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 40 sec.  The peak count rate
was ~2300 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 13:18:03.7 UT, 96.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 314.20310,
41.08996 which is equivalent to:
   RA(J2000)  = 20h 56m 48.74s
   Dec(J2000) = +41d 05' 23.9"
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This
location is 86 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (7.76 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.3
(+2.57/-1.47) x 10^22 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 8.64e-10 erg cm^-2 s^-1 (0.2-10

UVOT data is unavailable at this time. 

Burst Advocate for this burst is A. Y. Lien (yarleen AT 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information:
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