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GCN Circular 30413

Subject
GRB 210708A: Swift detection of a burst
Date
2021-07-08T02:40:32Z (3 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
B. Sbarufatti (PSU), H. A. Krimm (NSF), S. Laha (GSFC/UMBC/CRESST),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 02:25:37 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210708A (trigger=1059460).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 173.699, -49.187 which is 
   RA(J2000) = 11h 34m 48s
   Dec(J2000) = -49d 11' 11"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 10 sec.  The peak count rate
was ~1300 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 02:26:37.5 UT, 60.5 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 173.73706, -49.15179 which is
equivalent to:
   RA(J2000)  = 11h 34m 56.89s
   Dec(J2000) = -49d 09' 06.4"
with an uncertainty of 12.2 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 (1.58 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.5
(+3.01/-2.55) x 10^21 cm^-2 (90% confidence). 

UVOT data is not immediately available, possibly due to a bright
star (mag=5.5) within 1 arcminute of the XRT location. 

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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