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GCN Circular 7635

GRB080319A: MAGIC telescope GeV observation
2008-04-20T19:22:07Z (16 years ago)
Markus Garczarczyk at MPI/MAGIC <>
Garczarczyk M., Gaug M., Antonelli A., Bastieri D., Covino S., 
Galante N., La Barbera A., Longo F. and Scapin V. for the MAGIC 

The MAGIC Imaging Atmospheric Cherenkov Telescope performed a follow-up 
observation of the BAT burst GRB080319A (GCN circular 7426, Pagani et 
al.). We received the GCN alert at 05:46:45 UT (T0+63s), data taking with 
MAGIC started at 05:50:32 UT (T0+290s). The observation continued for 
1736s, starting at the zenith angle of 35 degrees.

No evidence for VHE gamma-ray emission above the analysis threshold of
175 GeV was found. The observation was carried out in (less sensitive) 
moon-observation mode.

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, including a 30% 
systematic uncertainty on the telescope efficiency:

E (125- 175 GeV): 0.57 * 10^-10 erg/cm^2/s
E (175- 300 GeV): 0.11 * 10^-10 erg/cm^2/s
E (300-1000 GeV): 0.06 * 10^-10 erg/cm^2/s

for a time window from 05:50:01 UT to 06:19:01 UT.

For the same time window, we can also exclude emission of a constant flux 
in any 100s time bin smaller than:

E (125- 175 GeV): 13.97 * 10^-10 erg/cm^2/s
E (175- 300 GeV):  4.34 * 10^-10 erg/cm^2/s
E (300-1000 GeV):  1.46 * 10^-10 erg/cm^2/s

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