[vsnet-grb-info 7298] GRB090113: MAGIC telescope GeV observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8867
SUBJECT: GRB090113: MAGIC telescope GeV observation
DATE:    09/02/01 19:34:26 GMT
FROM:    Markus Garczarczyk at MPI/MAGIC  <garcz at mppmu.mpg.de>

Becerra Gonzalez J. (IAC Tenerife), Gaug M. (IAC Tenerife), 
Antonelli L.A. (INAF Rome), Bastieri D. (Univ. Padova),
Becker J. (Univ. Dortmund), Carosi A. (INAF Rome),
Covino S. (INAF Rome), Galante N. (MPI Munich),
Garczarczyk M. (IFAE Barcelona), La Barbera A. (INAF Palermo),
Longo F. (INFN Trieste), Lorenz E. (ETH Zuerich),
Paoletti R. (Univ. Siena), Persic M. (INAF and INFN Trieste),
Scapin V. (Univ. Udine), Spiro S. (INAF Rome)
and Teshima M.(MPI Munich) for the MAGIC collaboration

The MAGIC Imaging Atmospheric Cherenkov Telescope performed a follow-up 
observation of the BAT burst GRB090113 (GCN circular 8804, Krimm et al.). 
We received the GCN alert at 18:41:01 UT (T0+20s), before the sunset. Data 
taking with MAGIC started at 20:06:08 UT (T0+4603s), when the GRB zenith 
angle reached 5 degrees. The observation continued for 9405 s.

No evidence for VHE gamma-ray emission above the analysis threshold of
94 GeV was found. The observation was carried out in (less sensitive) 
moon-observation mode from 21:39:01 UT on.

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 (  80- 125 GeV): 0.54 * 10^-10 erg cm^-2 s^-1
E ( 125- 175 GeV): 0.99 * 10^-10 erg cm^-2 s^-1
E ( 175- 300 GeV): 0.10 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 0.08 * 10^-10 erg cm^-2 s^-1
for a time window from 20:06:01 UT to 21:37:01 UT

E ( 125- 175 GeV): 0.93 * 10^-10 erg cm^-2 s^-1
E ( 175- 300 GeV): 0.23 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 0.08 * 10^-10 erg cm^-2 s^-1
for a time window from 21:39:01 UT to 22:32:01 UT

We can also exclude emission of a constant flux in any 100s time bin 
smaller than:

E (  80- 125 GeV): 13.89 * 10^-10 erg cm^-2 s^-1
E ( 125- 175 GeV): 8.88 * 10^-10 erg cm^-2 s^-1
E ( 175- 300 GeV): 3.40 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 1.22 * 10^-10 erg cm^-2 s^-1
for a time window from 20:06:01 UT to 21:37:01 UT

E ( 125- 175 GeV): 13.20 * 10^-10 erg cm^-2 s^-1
E ( 175- 300 GeV): 3.88 * 10^-10 erg cm^-2 s^-1
E ( 300-1000 GeV): 2.30 * 10^-10 erg cm^-2 s^-1
for a time window from 21:39:01 UT to 22:32:01 UT

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