TITLE:   GCN CIRCULAR
NUMBER:  28539
SUBJECT: GRB 201001A: Swift detection of a burst
DATE:    20/10/01 10:19:55 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

K. K. Simpson (PSU), J.D. Gropp (PSU), H. A. Krimm (NSF),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 09:58:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 201001A (trigger=998344).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 110.070, -2.210 which is 
   RA(J2000) = 07h 20m 17s
   Dec(J2000) = -02d 12' 36"
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 30 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 10:00:47.5 UT, 116.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 110.0806, -2.2103 which
is equivalent to:
   RA(J2000)  = 07h 20m 19.33s
   Dec(J2000) = -02d 12' 37.2"
with an uncertainty of 4.4 arcseconds (radius, 90% containment). This
location is 38 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 119 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 19.6 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 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.12. 

Burst Advocate for this burst is K. K. Simpson (kira.simpson1984 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/)