GCN Circular 28337

B. Sbarufatti (PSU), P. A. Evans (U Leicester),
A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 07:09:26 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200901B (trigger=994165).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 217.879, -38.716 which is 
   RA(J2000) = 14h 31m 31s
   Dec(J2000) = -38d 42' 58"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual with an image trigger, 
the available BAT light curve shows no significant structure. 

The XRT began observing the field at 07:12:16.1 UT, 169.7 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 217.8572, -38.7117 which is equivalent to:
   RA(J2000)  = 14h 31m 25.73s
   Dec(J2000) = -38d 42' 42.1"
with an uncertainty of 5.5 arcseconds (radius, 90% containment). This
location is 63 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 1.11e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
175 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
0.09. 

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/)