[vsnet-grb-info 4626] GRB070412: MAGIC telescope GeV observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6382
SUBJECT: GRB070412: MAGIC telescope GeV observation
DATE:    07/05/07 17:05:18 GMT
FROM:    Markus Garczarczyk at MPI/MAGIC  <garcz at mppmu.mpg.de>

Galante N., Garczarczyk M., Gaug M., Scapin V., Bastieri D. and Longo F.
report for the MAGIC collaboration:

The MAGIC Imaging Atmospheric Cherenkov Telescope performed a follow-up
observation of the SWIFT-BAT burst GRB070412 (GCN circular 6273, Romano P.
et al.). We received the delayed GCN alert at T0+647s, The data taking
with MAGIC started at T0+701s, 27s after the alert income. We observed the
sky positon for 124min on April 12th and for further 178min on April 13th,
starting at T0+7.6x10^4s.

No evidence for VHE gamma-ray emission above the analysis threshold of
90 GeV was found in both data sets. 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)   : 1.03 x 10^(-11) erg/cm^2/s
E(125-175 GeV)  : 0.31 x 10^(-11) erg/cm^2/s
E(175-300 GeV)  : 0.75 x 10^(-11) erg/cm^2/s
E(300-1000 GeV) : 0.77 x 10^(-11) erg/cm^2/s

The upper limits correspond to the time period between T0+701s and
T0+8181s.

We can also exclude emission of a constant flux during our observation in
any 100s time bin higher than:

E(80-200 GeV)   : 2.2 x 10^(-9) erg/cm^2/s
E(200-1000 GeV) : 0.5 x 10^(-9) erg/cm^2/s

for the time period between T0+701s and T0+8181s, and:

E(80-200 GeV)   : 2.5 x 10^(-9) erg/cm^2/s
E(200-1000 GeV) : 0.5 x 10^(-9) erg/cm^2/s

for the time period between T0+7.6x10^4 s and T0+8.7x10^4 s.

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