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GCN Circular 24595

Subject
GRB 190519A: Swift detection of a burst
Date
2019-05-19T07:46:35Z (5 years ago)
From
Caryl Gronwall at PSU/Swift-UVOT <caryl@swift.psu.edu>
T. N. Ukwatta (LANL), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC),
C. Gronwall (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC) and
K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 07:25:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190519A (trigger=904394).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 114.764, -38.824 which is 
   RA(J2000) = 07h 39m 03s
   Dec(J2000) = -38d 49' 26"
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. In addition, there might be
a weaker pulse that starts at ~ T-50 s. The peak count rate
was ~5500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 07:27:04.3 UT, 85.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 114.7673,
-38.8052 which is equivalent to:
   RA(J2000)  = 07h 39m 04.14s
   Dec(J2000) = -38d 48' 18.7"
with an uncertainty of 2.0 arcseconds (radius, 90% containment). This
location is 68 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (4.31 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.6
(+2.17/-1.96) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 4.35e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
150 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. 
Results from the list of sources generated on-board are not available at this
time. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.42. 

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/)
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