[vsnet-grb-info 3737] GRB060825: MAGIC telescope GeV observation

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5571
SUBJECT: GRB060825: MAGIC telescope GeV observation
DATE:    06/09/13 19:34:57 GMT
FROM:    Markus Garczarczyk at MPI/MAGIC  <garcz at mppmu.mpg.de>

Gaug M. and Garczarczyk M., Bastieri D., Fagiolini M., Galante N.,
Longo F., Mizobuchi S., Picciolini A., Scampin V. and Stamerra A.
report for the MAGIC collaboration:

The MAGIC Imaging Atmospheric Cherenkov Telescope performed a follow-up
observation of the SWIFT-BAT burst GRB060825 (GCN circular 5478, Fenimore
E. et al.). We received the GCN alert at T0+19s. The telescope slewed fast
to the GRB sky coordinates and started data taking 38s after the alert, at
T0+57s. In total 33min of data from the GRB sky coordinates were
accumulated. Due to the short duration of the burst (T90 = 8.8s), only the
early afterglow phase was observed. The observation overlapped with the
small x-ray flare detected by SWIFT-XRT (GCN circular 5479, Beardmore A.P.
et al.), centered at T0+220s.

No evidence for VHE emission above the analysis threshold of 90GeV was
found. A preliminary analysis, for the hypothesis of steady emission and
assumption of a differential photon spectral index of -2.5, yields the
following 95% CL differential flux upper limits (inc. 30% systematic error
on the absolute flux level):

E(80-125 GeV)   : 1.8 x 10^(-10) erg/cm^2/s
E(125-175 GeV)  : 1.9 x 10^(-10) erg/cm^2/s
E(175-300 GeV)  : 1.2 x 10^(-10) erg/cm^2/s
E(300-1000 GeV) : 0.6 x 10^(-10) erg/cm^2/s

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