[vsnet-grb-info 6576] GRB080825C: Fermi-LAT observations

Sat Sep 6 02:45:56 JST 2008

TITLE:   GCN CIRCULAR
NUMBER:  8183
SUBJECT: GRB080825C: Fermi-LAT observations
DATE:    08/09/05 17:45:46 GMT
FROM:    Aurelien Bouvier at Stanford  <bouvier at stanford.edu>

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A. Bouvier (SLAC), D. Band (GSFC), J. Bregeon (INFN Pisa), J. Chiang  
(SLAC), S. Cutini (ASDC), B. Dingus (LANL), N. Gehrels (GSFC), Y.  
Fukazawa (Hiroshima U), M. Hayashida (SLAC), F. Longo (INFN Trieste),  
J. McEnery (GSFC), M. Ohno (JAXA), N. Omodei (INFN Pisa), V. Pelassa  
(LPTA), F. Piron (LPTA), D. Sanchez (LLR), J. Scargle (NASA Ames), H.  
Tajima (SLAC), T. Tanaka (SLAC), G. Thayer (SLAC) on behalf of the  
Fermi LAT team:

We report a detection by the Fermi Large Area Telescope (LAT) of  
emission from GRB080825C, which was triggered by the Fermi Gamma-ray  
Burst Monitor (GBM) at 14:13:48 UT on August 25th 2008 (GCN 8141 by  
Van der Horst et al.). The angle of the GBM best localization (ra,  
dec=232.2,-4.6) with the LAT boresight was 60 deg at the time of the  
trigger which is on the edge of our field of view.

The data from the Fermi LAT shows a significant increase in the event  
rate within 10 degree of the GBM localization and up to 35 seconds  
after the GBM trigger that is spatially and temporally correlated  
with the GBM emission with a significance of more than 5 sigma. All  
the LAT events detected during the GBM emission have energies below 1  
GeV.

The best LAT on-ground localization is found to be  
RA,DEC=233.96,-4.72 deg with a 90% containment radius of 1.5 deg  
(statistical+systematics; 68% containment radius: 0.95 deg) which is  
consistent with the GBM localization.

This circular is an official product of the Fermi LAT team.
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<html><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; "><div style=3D"margin-top: 0px; =
margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font =
face=3D"Helvetica" size=3D"3" style=3D"font: 12.0px Helvetica">A. =
Bouvier (SLAC), D. Band (GSFC), J. Bregeon (INFN Pisa), J. Chiang =
(SLAC), S. Cutini (ASDC), B. Dingus (LANL), N. Gehrels (GSFC), =
Y.=A0Fukazawa (Hiroshima U), M. Hayashida (SLAC), F. Longo (INFN =
Trieste), J. McEnery (GSFC), M. Ohno (JAXA), N. Omodei (INFN Pisa), V. =
Pelassa (LPTA), F. Piron (LPTA), D. Sanchez (LLR), J. Scargle (NASA =
Ames), H. Tajima (SLAC), T. Tanaka (SLAC), G. Thayer (SLAC) on behalf of =
the Fermi LAT team:</font></div><div style=3D"margin-top: 0px; =
margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal =
normal normal 12px/normal Helvetica; min-height: 14px; "><br></div><div =
style=3D"margin-top: 0px; margin-right: 0px; margin-bottom: 0px; =
margin-left: 0px; "><font face=3D"Helvetica" size=3D"3" style=3D"font: =
12.0px Helvetica">We report a detection by the Fermi Large Area =
Telescope (LAT) of emission from GRB080825C, which was triggered by the =
Fermi Gamma-ray Burst Monitor (GBM) at 14:13:48 UT on August 25th 2008 =
(GCN 8141 by Van der Horst et al.). The angle of the GBM best =
localization (ra, dec=3D232.2,-4.6) with the LAT boresight was 60 deg at =
the time of the trigger which is on the edge of our field of =
view.</font></div><div style=3D"margin-top: 0px; margin-right: 0px; =
margin-bottom: 0px; margin-left: 0px; font: normal normal normal =
12px/normal Helvetica; min-height: 14px; "><br></div><div =
style=3D"margin-top: 0px; margin-right: 0px; margin-bottom: 0px; =
margin-left: 0px; "><font face=3D"Helvetica" size=3D"3" style=3D"font: =
12.0px Helvetica">The data from the Fermi LAT shows a significant =
increase in the event rate within 10 degree of the GBM localization and =
up to 35 seconds after the GBM trigger that is spatially and temporally =
correlated with the GBM emission with a significance of more than 5 =
sigma. All the LAT events detected during the GBM emission have energies =
below 1 GeV.</font></div><div style=3D"margin-top: 0px; margin-right: =
0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal =
12px/normal Helvetica; min-height: 14px; "><br></div><div =
style=3D"margin-top: 0px; margin-right: 0px; margin-bottom: 0px; =
margin-left: 0px; "><font face=3D"Helvetica" size=3D"3" style=3D"font: =
12.0px Helvetica">The best LAT on-ground localization is found to be =
RA,DEC=3D233.96,-4.72 deg with a 90% containment radius of 1.5 deg =
(statistical+systematics; 68% containment radius: 0.95 deg) which is =
consistent with the GBM localization.</font></div><div =
style=3D"margin-top: 0px; margin-right: 0px; margin-bottom: 0px; =
margin-left: 0px; font: normal normal normal 12px/normal Helvetica; =
min-height: 14px; "><br></div><div style=3D"margin-top: 0px; =
margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><font =
face=3D"Helvetica" size=3D"3" style=3D"font: 12.0px Helvetica">This =
circular is an official product of the Fermi LAT team.</font></div>
</body></html>=

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