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GCN Circular 29487

Subject
GRB 210212A: Swift detection of a burst
Date
2021-02-12T04:50:37Z (3 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
E. Troja (NASA/GSFC/UMCP), J. A. Kennea (PSU), N. J. Klingler (PSU),
H. A. Krimm (NSF), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU),
M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 04:25:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210212A (trigger=1032183).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 72.261, +7.234 which is 
   RA(J2000) = 04h 49m 03s
   Dec(J2000) = +07d 14' 01"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a 
structure with a duration of about 50 sec.  The peak count rate
was ~1200 counts/sec (15-350 keV), at ~6 sec after the trigger. 

The XRT began observing the field at 04:27:00.9 UT, 103.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 72.2666,
7.2693 which is equivalent to:
   RA(J2000)  = 04h 49m 03.99s
   Dec(J2000) = +07d 16' 09.5"
with an uncertainty of 3.8 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.  We cannot determine whether the source
is fading at the present time. No spectrum from the promptly downlinked
event data is yet available to determine the column density. 

The initial flux in the 2.5 s image was 9.74e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
270 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 100% of the
XRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.094. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
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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