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GCN Circular 33176

Subject
GRB 230116D: Swift detection of a burst
Date
2023-01-16T21:23:25Z (a year ago)
From
David Palmer at LANL <palmer@lanl.gov>
E. Sonbas (Adiyaman Univ.), R. A. J. Eyles-Ferris (U Leicester),
C. Gronwall (PSU), J.D. Gropp (PSU),
N. J. Klingler (GSFC/UMBC/CRESSTII), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (AGU) and M. A. Williams (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 21:04:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 230116D (trigger=1149293).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 98.594, 49.840d which is 
   RA(J2000) = 06h 34m 23s
   Dec(J2000) =  +49d 50' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Due to a communications gap the BAT
lightcurve before T+8 s is not immediately available, but
the later lightcurve indicates activity out to at least T+30 s. 

The XRT began observing the field at 21:06:54.1 UT, 130.9 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 98.61709, 49.87257
which is equivalent to:
   RA(J2000)  = 06h 34m 28.10s
   Dec(J2000) = +49d 52' 21.3"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 128 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
https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.65
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 133 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers none of
the XRT error circle. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. The list of sources is typically
complete to about 18 mag. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.112. 

Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.com). 
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: http://www.swift.psu.edu/)
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