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GCN Circular 9491

Subject
GRB 090607: Swift detection of a burst
Date
2009-06-07T06:11:45Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), M. M. Chester (PSU),
C. Guidorzi (U Ferrara), H. A. Krimm (CRESST/GSFC/USRA),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. N. Ukwatta (GSFC/GWU) and H. Ziaeepour (UCL-MSSL) report on behalf
of the Swift Team:

At 05:30:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090607 (trigger=354299).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 191.209, +44.130 which is 
   RA(J2000)  = 12h 44m 50s
   Dec(J2000) = +44d 07' 47"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several spikes
with a duration of about 5 sec.  The peak count rate
was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 05:31:27 UT, 70 seconds
after the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 191.16903, 44.10541 which
is equivalent to:
   RA(J2000)  = 12h 44m 40.57s
   Dec(J2000) = +44d 06' 19.5"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 136 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 (1.84e+20
cm^-2, Kalberla et al. 2005), with an excess column of 4.1
(+2.44/-2.19) x 10^21 cm^-2 (90% confidence). 

Because of the presence of a magnitude 6.3 star in the UVOT
Field of View, 2.3 arcmin from the XRT location, 
UVOT will not be able to observe this burst. 

There was some extra delay in processing this burst.  It was originally
a subthreshold trigger (Image_signif=6.49 sigma).  The automated processing
for the XRT position had a problem.  This circular is based on manual processing. 

Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.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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