GCN Circular 21191

K. L. Page (U Leicester), A. Cholden-Brown (PSU),
N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC) and
F. E. Marshall (NASA/GSFC) report on behalf of the Swift Team:

At 19:08:50 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170604A (trigger=755867).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 342.645, -15.414 which is 
   RA(J2000) = 22h 50m 35s
   Dec(J2000) = -15d 24' 50"
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 25 sec.  The peak count rate
was ~2400 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 19:10:55.1 UT, 124.7 seconds after
the BAT trigger. No source was detected in the 2.5-s promptly available
image. However, the XRT TDRSS light curve suggests the presence of a bright,
fading  source; since no Photon Counting mode data were collected, no prompt 
source localisation can be performed. We are waiting for the full dataset to 
detect and localise the XRT counterpart. 

No results from UVOT are available at this time. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 
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.)