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GCN Circular 11087

Subject
GRB 100814A: Swift detection of a burst with an optical afterglow
Date
2010-08-14T04:22:40Z (14 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), N. P. M. Kuin (UCL-MSSL),
O. M. Littlejohns (U Leicester), C. B. Markwardt (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
C. J. Saxton (UCL-MSSL), R. L. C. Starling (U Leicester),
E. Troja (NASA/GSFC/ORAU) and T. N. Ukwatta (GSFC/GWU) report on
behalf of the Swift Team:

At 03:50:11 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100814A (trigger=431605).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 22.481, -17.986 which is 
   RA(J2000) = 01h 29m 55s
   Dec(J2000) = -17d 59' 07"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed three separate
peaks over a total interval of at least 150 sec.  The peak count rate
was ~6000 counts/sec (15-350 keV), at ~6 sec after the trigger. 

The XRT began observing the field at 03:51:38.6 UT, 87.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 22.47220,
-17.99643 which is equivalent to:
   RA(J2000)  = 01h 29m 53.33s
   Dec(J2000) = -17d 59' 47.1"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 48 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 consistent with the Galactic value of
1.75e+20 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 6.18e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter
starting 153 seconds after the BAT trigger.  A bright optical afterglow 
candidate was found at RA=22.4749, dec=-17.9932 which is
  RA = 01h 29m 53.98s
  Dec=-17d 59m 35.5s
(J2000).  The estimated magnitude is U=16.8 . 


Burst Advocate for this burst is C. J. Saxton (cjs2 AT mssl.ucl.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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