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GCN Circular 30447

Subject
GRB 210712A: Swift detection of a burst
Date
2021-07-12T09:58:21Z (3 years ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
B. Sbarufatti (PSU), H. A. Krimm (NSF) and K. L. Page (U Leicester)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 09:43:11 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210712A (trigger=1059881).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 97.337, -35.393 which is 
   RA(J2000) = 06h 29m 21s
   Dec(J2000) = -35d 23' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 20 sec, followed by lower-level 
extended emission.  The peak count rate was ~2600 counts/sec (15-350 keV), 
at ~0 sec after the trigger. 

The XRT began observing the field at 09:44:32.5 UT, 80.6 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 97.3319,
-35.3717 which is equivalent to:
   RA(J2000)  = 06h 29m 19.66s
   Dec(J2000) = -35d 22' 18.0"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at https://www.swift.ac.uk/sper.  We cannot determine
whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (8.88 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.5
(+5.28/-4.30) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 3.52e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 90 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 0.076. 

Burst Advocate for this burst is B. Sbarufatti (bxs60 AT psu.edu). 
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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