GCN Circular 24927

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

At 23:52:59 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190630C (trigger=912239).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 293.908, -32.751 which is 
   RA(J2000) = 19h 35m 38s
   Dec(J2000) = -32d 45' 03"
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 120 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 23:55:28.8 UT, 149.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 293.87874,
-32.74273 which is equivalent to:
   RA(J2000)  = 19h 35m 30.90s
   Dec(J2000) = -32d 44' 33.8"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 93 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 http://www.swift.ac.uk/sper. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 1.02e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 157 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
0.11. 

This source lies within the current (Sector 13) field-of-view of TESS camera 1. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta 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/)