TITLE:   GCN CIRCULAR
NUMBER:  25463
SUBJECT: GRB 190824A: Swift detection of a burst
DATE:    19/08/24 15:03:25 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

V. D'Elia (SSDC), E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), J.D. Gropp (PSU), N. J. Klingler (PSU),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 14:46:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190824A (trigger=922107).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 215.329, -41.902, which is 
   RA(J2000)  =  14h 21m 19s
   Dec(J2000) = -41d 54' 07"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple peaks
with a total duration of about 120 sec.  The peak count rate
was ~3200 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 14:55:24.0 UT, 524.4 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 215.3045,
-41.8943 which is equivalent to:
   RA(J2000)  = 14h 21m 13.09s
   Dec(J2000) = -41d 53' 39.3"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 71 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. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 568 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
0.12. 

Burst Advocate for this burst is V. D'Elia (delia AT ssdc.asi.it). 
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/)