TITLE:   GCN CIRCULAR
NUMBER:  39835
SUBJECT: GRB 250322A: Swift detection of a short burst
DATE:    25/03/22 16:26:08 GMT
FROM:    David Palmer at LANL <palmer@lanl.gov>

R. Gupta (NASA GSFC), R. Brivio (INAF-OAB), M. Ferro (INAF-OAB),
J. A. Kennea (PSU), H. A. Krimm (NSF), M. J. Moss (GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), M. H. Siegel (PSU)
and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 16:06:12 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 250322A (trigger=1297832).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 106.734, +7.199 which is 
   RA(J2000) = 07h 06m 56s
   Dec(J2000) = +07d 11' 56"
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 1 sec.  The peak count rate
was ~10,000 counts/sec (15-350 keV), at ~0 sec after the trigger.

The XRT began observing the field at 16:07:25.4 UT, 73 seconds
after the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source with an enhanced position: RA, Dec 106.76025,
7.19285 which is equivalent to:
   RA(J2000)  = 07h 07m 02.46s
   Dec(J2000) = +07d 11' 34.2"
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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.70
x 10^21 cm^-2 (Willingale et al. 2013).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 76 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 0.154.

Burst Advocate for this burst is R. Gupta (rahulbhu.c157 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/)