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GCN Circular 9793

Subject
GRB 090814: Swift detection of a burst
Date
2009-08-14T01:13:22Z (15 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
T. N. Ukwatta (GSFC/GWU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),
D. N. Burrows (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Gronwall (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
M. Stamatikos (OSU/NASA/GSFC) and M. A. Stark (PSU) report on behalf
of the Swift Team:

At 00:52:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090814 (trigger=359951).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 239.611, +25.599 which is 
   RA(J2000) = 15h 58m 27s
   Dec(J2000) = +25d 35' 57"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple weak peaks 
with a total duration of about 30 seconds.  The peak count rate
was ~500 counts/sec (15-350 keV), at 10 sec before the trigger. 

The XRT began observing the field at 00:54:58.3 UT, 159.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
239.6095, 25.6310 which is equivalent to:
   RA(J2000)  = 15h 58m 26.29s
   Dec(J2000) = +25d 37' 51.7"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 115 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
4.76e+20 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 1.65e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 169 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
UL at the XRT position is 19.2 mag.   No correction has been made for
the expected extinction corresponding to E(B-V) of  0.08. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 
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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