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GCN Circular 9430

Subject
GRB 090529: Swift detection of a burst
Date
2009-05-29T14:40:28Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (NASA/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester),
O. Godet (U Leicester), C. Gronwall (PSU), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), V. Mangano (INAF-IASFPA),
J. Mao (INAF-OAB), R. Margutti (Univ Bicocca&OAB),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
B. Sbarufatti (INAF-IASFPA), M. H. Siegel (PSU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 14:12:35 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090529 (trigger=353540).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 212.474, +24.437 which is 
   RA(J2000)  = 14h 09m 54s
   Dec(J2000) = +24d 26' 13"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve does not show anything
but this is typical for an image trigger. 

The XRT began observing the field at 14:15:52.3 UT, 197.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 212.46882,
24.45889 which is equivalent to:
   RA(J2000)  = 14h 09m 52.52s
   Dec(J2000) = +24d 27' 32.0"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 80 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 (1.61e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2.9
(+1.72/-1.51) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.48e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 205 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 typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.02. 

Burst Advocate for this burst is T. Sakamoto (Taka.Sakamoto 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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