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GCN Circular 6267

Subject
GRB 070411: Swift detection of a burst with optical afterglow
Date
2007-04-11T20:43:42Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
A. Moretti (INAF-OAB), S. D. Barthelmy (GSFC), P. J. Brown (PSU),
D. N. Burrows (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC),
G. Cusumano (INAF-IASFPA), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU),
H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
C. Pagani (PSU), D. M. Palmer (LANL),
P. Romano (Univ. Bicocca & INAF-OAB), T. Sakamoto (NASA/ORAU),
B. Sbarufatti (INAF-IASFPA), M. Stamatikos (NASA/ORAU),
R. L. C. Starling (U Leicester), G. Tagliaferri (INAF-OAB),
D. E. Vanden Berk (PSU), S. D. Vergani (DIAS-DCU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:

At 20:12:33 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070411 (trigger=275087).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 107.338, +1.083 which is 
   RA(J2000)  =  07h 09m 21s
   Dec(J2000) = +01d 04' 57"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows an initial weak peak
starting at T-1 sec and fading by T+5 sec and then a stronger second peak
from T+50 to T+90 sec with an amplitude of ~1000 cnts/sec
in the 15-350 keV band. 

The XRT began observing the field at 20:14:09 UT, 96 seconds after the
BAT trigger. XRT found an uncatalogued X-ray source
located at RA, Dec 107.3327, +1.0632 which is
   RA(J2000)  =  07h 09m 19.8s
   Dec(J2000) =  01d 03' 47.5"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). 
This location is 74 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 5.1e-09 erg/cm2/s (0.2-10 keV). 

UVOT took a finding chart exposure of nominal 100 seconds with the
White (160-650 nm) filter starting 244 seconds after the BAT trigger. 
An afterglow candidate has been found in the initial data products. 
The 2.7'x2.7' region for the list of sources generated on-board
covers 100% of the XRT error circle. A source is detected at

 RA =  07:09:19.93
Dec = +01:03:52.6 

with an estimated uncertainty of +/-0.5 arcsec. The
estimated magnitude in the White filter is 18.7. No correction has
been made for the large, but uncertain extinction corresponding
to a reddening of 0.3 mag.
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