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GCN Circular 27173

Subject
GRB 200224A: Swift detection of a burst
Date
2020-02-24T03:41:23Z (4 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
T. N. Ukwatta (LANL), E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA),
V. D'Elia (SSDC), J. A. Kennea (PSU), N. J. Klingler (PSU),
S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 03:24:49 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200224A (trigger=958141).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 248.794, +41.675 which is 
   RA(J2000) = 16h 35m 11s
   Dec(J2000) = +41d 40' 31"
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 30 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 03:26:26.9 UT, 97.7 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 248.7668, 41.6123 which
is equivalent to:
   RA(J2000)  = 16h 35m 04.04s
   Dec(J2000) = +41d 36' 44.1"
with an uncertainty of 2.9 arcseconds (radius, 90% containment). This
location is 237 arcseconds from the BAT onboard position. 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 consistent with the Galactic value of 8.91
x 10^19 cm^-2 (Willingale et al. 2013). 

UVOT results will be reported later. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.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/)

[GCN OPS NOTE(24feb20): This is the second Circular in the sequence of 8 circulars
which were all labeled A because of the sequence assigner being offline.  
This circular was correctly labelled A.]
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