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GCN Circular 9135

Subject
GRB 090417B: Swift detection of a burst
Date
2009-04-17T15:41:13Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
B. Sbarufatti (INAF-IASFPA), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),
D. N. Burrows (PSU), P.A. Curran (MSSL-UCL),
P. A. Evans (U Leicester), O. Godet (U Leicester),
C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (MSSL),
V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB),
R. Margutti (Univ Bicocca&OAB), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), P. Romano (INAF-IASFPA),
B. A. Rowlinson (U Leicester), M. H. Siegel (PSU),
M. Stamatikos (NASA/ORAU) and T. N. Ukwatta (GSFC/GWU) report on
behalf of the Swift Team:

At 15:20:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090417B (trigger=349450).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 209.706, +47.000 which is 
   RA(J2000)  =  13h 58m 49s
   Dec(J2000) = +47d 00' 01"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The TDRSS BAT light does not show much 
for this 320-sec image trigger (as is typical for image triggers). 

The XRT began observing the field at 15:26:30.4 UT, 387.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued and fading X-ray source 
located at RA, Dec 209.6931, +47.0170 which is equivalent to:
   RA(J2000)  = 13h 58m 46.34s
   Dec(J2000) = +47d 01' 01.2"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 68 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 2.77e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 395 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 upper limit is white = 20.1 mag. 
No correction has been made for the expected extinction corresponding to E(B-V) 
of 0.02. 

Burst Advocate for this burst is B. Sbarufatti (sbarufatti AT ifc.inaf.it). 
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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