GCN Circular 21793

C. B. Markwardt (NASA/GSFC), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), J. A. Kennea (PSU),
K. L. Page (U Leicester), J. L. Racusin (NASA/GSFC) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 12:49:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170903A (trigger=770528).  Swift did not slew due to an observing
constraint.  The BAT on-board calculated location is 
RA, Dec 254.512, +34.983, which is 
   RA(J2000)  =  16h 58m 03s
   Dec(J2000) = +34d 59' 01"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a few peaks
with a total duration of about 30 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~4 sec after the trigger. 

Due to an observing constraint, Swift will not slew until T0+49.5
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt AT nasa.gov). 
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/too.html.)