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GCN Circular 10784

Subject
GRB 100522A: Swift detection of a burst
Date
2010-05-22T04:14:56Z (14 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
E. Troja (NASA/GSFC/ORAU), A. P. Beardmore (U Leicester),
M. M. Chester (PSU), J. M. Gelbord (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), C. Pagani (U Leicester),
D. M. Palmer (LANL), R. L. C. Starling (U Leicester),
T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the
Swift Team:

At 03:45:52 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100522A (trigger=422783).  Swift slewed immediately to 
the burst.  The BAT on-board calculated location is 
RA, Dec 6.983, +9.417 which is 
   RA(J2000) = 00h 27m 56s
   Dec(J2000) = +09d 25' 03"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a first pair of peaks near T0 with a duration of 
about 5 sec and a second fainter and softer pair of peaks near T+30 s.  
The peak count rate was ~15,000 counts/sec (15-350 keV), at ~0 sec 
after the trigger. 

The XRT began observing the field at 03:46:57.7 UT, 65.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
6.9867, 9.4023 which is equivalent to:
   RA(J2000)  = 00h 27m 56.82s
   Dec(J2000) = +09d 24' 08.1"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 54 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 (3.98e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2.7
(+2.46/-2.10) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 2.40e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 73 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 3-sigma
upper limit at the XRT position is 18.5 mag. No  correction has been
made for the expected extinction corresponding to E(B-V) of  0.06. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
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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