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GCN Circular 22630

Subject
GRB 180411A: Swift detection of a burst
Date
2018-04-11T12:48:19Z (6 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
Z. Liu (NAOC/U. Leicester), A. P. Beardmore (U Leicester),
A. A. Breeveld (UCL-MSSL), A. Deich (PSU), J.D. Gropp (PSU),
J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 12:27:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180411A (trigger=824451).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 356.829, +66.791 which is 
   RA(J2000) = 23h 47m 19s
   Dec(J2000) = +66d 47' 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 100 sec.  The peak count rate
was ~8000 counts/sec (15-350 keV), at ~53 sec after the trigger. 

The XRT began observing the field at 12:28:50.4 UT, 66.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 356.85453,
66.77831 which is equivalent to:
   RA(J2000)  = 23h 47m 25.09s
   Dec(J2000) = +66d 46' 41.9"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 58 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 (8.31 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 1.2
(+0.97/-0.75) x 10^22 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.35e-08 erg cm^-2 s^-1 (0.2-10
keV). 

There are no UVOT data available at the present time. 

Burst Advocate for this burst is Z. Liu (zl182 AT leicester.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.)
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