GCN Circular 24472

M. G. Bernardini (INAF-OAB), H. A. Krimm (NSF/USRA),
N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester),
B. Sbarufatti (PSU) and A. Tohuvavohu (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 07:14:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190511A (trigger=903158).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 126.436, -20.242 which is 
   RA(J2000) = 08h 25m 45s
   Dec(J2000) = -20d 14' 30"
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 20 sec.  The peak count rate
was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 07:16:51.2 UT, 122.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 126.44482, -20.25978 which
is equivalent to:
   RA(J2000)  = 08h 25m 46.76s
   Dec(J2000) = -20d 15' 35.2"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 70 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.  We
cannot determine whether the source is fading at the present time. 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 9.43e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of  95 seconds with the U filter starting
290 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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.09. 

Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini AT brera.inaf.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/)