GCN Circular 5789
Subject
GRB061028: MAGIC telescope GeV observation
Date
2006-11-08T11:45:41Z (18 years ago)
From
Markus Garczarczyk at MPI/MAGIC <garcz@mppmu.mpg.de>
Gaug M. and Garczarczyk M., Bastieri D., Fagiolini M., Galante N.,
Longo F., Mizobuchi S., Piccioli A., Scapin 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 GRB061028 (GCN circular 5762, Sakamoto
T. et al.). We received the GCN alert at T0+140s. The telescope slewed
immediately to the GRB sky coordinates and started data taking 29s after
the alert, at T0+169s. Due to the long time delay of the alert and the
burst duration of T90=106s, only the early afterglow phase could be
observed by MAGIC. Our observation window covered the weak tail emission
measured by BAT and the X-ray afterglow measured by XRT (Sakamoto T. et
al.). The observation continued for 100min.
No evidence for VHE gamma-ray emission above the analysis threshold of
110GeV 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(100-125 GeV) : 1.6 x 10^(-10) erg/cm^2/s
E(125-175 GeV) : 0.8 x 10^(-10) erg/cm^2/s
E(175-300 GeV) : 0.7 x 10^(-10) erg/cm^2/s
E(300-1000 GeV) : 0.3 x 10^(-10) erg/cm^2/s
The upper limits apply of the time window between T0+169s and T0+1969s
(the first 30min of the MAGIC data sample).
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