TITLE:   GCN CIRCULAR
NUMBER:  25848
SUBJECT: GRB 190926A: Swift detection of a burst
DATE:    19/09/26 10:06:20 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

A. Melandri (INAF-OAB), M. G. Bernardini (INAF-OAB),
P. D'Avanzo (INAF-OAB), P. A. Evans (U Leicester), J.D. Gropp (PSU),
H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC)
and K. L. Page (U Leicester) report on behalf of the Neil Gehrels
Swift Observatory Team:

At 09:52:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190926A (trigger=926515).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 100.599, +59.511 which is 
   RA(J2000) = 06h 42m 24s
   Dec(J2000) = +59d 30' 40"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Since this is an image trigger, the BAT 
light curve showed no significant structure. 

The XRT began observing the field at 09:54:30.4 UT, 134.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 100.5699, 59.5292 which is equivalent to:
   RA(J2000)  = 06h 42m 16.78s
   Dec(J2000) = +59d 31' 45.1"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 84 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 5.87e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 144 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 0.06. 

Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.it). 
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/)