[vsnet-grb-info 4265] GRB061217: MAGIC telescope GeV observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6060
SUBJECT: GRB061217: MAGIC telescope GeV observation
DATE:    07/01/30 18:19:08 GMT
FROM:    Markus Garczarczyk at MPI/MAGIC  <garcz at mppmu.mpg.de>

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

The MAGIC Imaging Atmospheric Cherenkov Telescope performed a follow-up
observation of the SWIFT-BAT burst GRB061217 (GCN circular 5926,
Barthelmy S.D. et al.). We received the GCN alert at T0+13s, however,
because of observation constraints, data taking with MAGIC started at
T0+773s, when the GRB zenith angle reached 60 degree. The observation
continued for 66min.

No evidence for VHE gamma-ray emission above the analysis threshold of
325 GeV 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(300-500 GeV)  : 0.53 x 10^(-10) erg/cm^2/s
E(500-1000 GeV) : 0.35 x 10^(-10) erg/cm^2/s

The upper limits apply of the time window between T0+773s and T0+2573s
(the first 30min of the MAGIC data sample).

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