TITLE:   GCN CIRCULAR
NUMBER:  22832
SUBJECT: GRB 180624A: Swift detection of a burst
DATE:    18/06/24 14:02:45 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

S. L. Gibson (U Leicester), S. D. Barthelmy (GSFC), A. Deich (PSU),
S. W. K Emery (UCL-MSSL), J.D. Gropp (PSU), K. L. Page (U Leicester),
T. Sakamoto (AGU) and M. H. Siegel (PSU) report on behalf of the Neil
Gehrels Swift Observatory Team:

At 13:49:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180624A (trigger=844192).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 318.071, -2.332, which is 
   RA(J2000)  =  21h 12m 17s
   Dec(J2000) = -02d 19' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Due to missing downlinked realtime data
in the light curve, we cannot give the BAT light curve description. 

The XRT began observing the field at 13:51:32.6 UT, 112.2 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 318.0951, -2.3397 which is equivalent to:
   RA(J2000)  = +21h 12m 22.82s
   Dec(J2000) = -02d 20' 22.9"
with an uncertainty of 5.2 arcseconds (radius, 90% containment). This
location is 91 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 1.93e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 118 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
0.05. 

Burst Advocate for this burst is S. L. Gibson (slg44 AT le.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.)