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GCN Circular 13727

GRB 120909A: Swift detection of a burst
2012-09-09T01:54:56Z (12 years ago)
David Palmer at LANL <>
S. Immler (CRESST/GSFC/UMD), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
S. T. Holland (STScI), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 01:42:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120909A (trigger=533060).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 275.685, -59.426 which is 
   RA(J2000)  =  18h 22m 44s
   Dec(J2000) = -59d 25' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows one, possibly two, peaks
with a duration of about 5 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 01:43:36.6 UT, 93.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 275.7388, -59.4485 which is equivalent to:
   RA(J2000)  = +18h 22m 57.31s
   Dec(J2000) = -59d 26' 54.6"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 127 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 7.55e-09 erg cm^-2 s^-1 (0.2-10

Because of an earth limb constraint, Swift slewed away before UVOT 
could take its initial exposures.  Subsequent orbits will include 
UVOT observations. 

Burst Advocate for this burst is S. Immler (stefan.immler AT 
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:
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