TITLE:   GCN CIRCULAR
NUMBER:  22973
SUBJECT: GRB 180720B: Swift detection of a burst
DATE:    18/07/20 14:34:56 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

M. H. Siegel (PSU), D. N. Burrows (PSU), A. Deich (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), S. J. LaPorte (PSU),
A. Y. Lien (GSFC/UMBC), M. J. Moss (George Washington University),
K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and
A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 14:21:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180720B (trigger=848890).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 0.530, -2.933 which is 
   RA(J2000) = 00h 02m 07s
   Dec(J2000) = -02d 56' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 150 sec.  The peak count rate
was ~50000 counts/sec (15-350 keV), at ~11 sec after the trigger. 

The XRT began observing the field at 14:23:11.0 UT, 86.5 seconds after
the BAT trigger. XRT found a bright, flaring and fading uncatalogued 
X-ray source located at RA, Dec 0.5279, -2.9170 which is equivalent to:
   RA(J2000)  = +00h 02m 6.70s
   Dec(J2000) = -02d 55' 01.2"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 58 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 0.1 s image was 6.59e-08 erg cm^-2 s^-1 (0.2-10
keV). 

No UVOT data is available yet. 

Burst Advocate for this burst is M. H. Siegel (siegel AT swift.psu.edu). 
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.)

[GCN OPS NOTE(21jul18):  In response to GCN Circular 22975, this 
archived copy of 22973 has been modified with the correct GRB maining
"A" --> "B".]