GRB 070920A
GCN Circular 6854
Subject
GRB070920A: MAGIC telescope GeV observation
Date
2007-10-06T08:21:21Z (18 years ago)
From
Nicola Galante at MPI,Muenchen <galante@mppmu.mpg.de>
Galante N. (MPI/Muenchen), Garczarczyk M. (MPI/Muenchen),
Gaug M. (IAC/Tenerife), Bastieri D. (U. Padova), Longo F. (INFN/Trieste)
and Scapin V. (U. Udine), for the MAGIC Collaboration
The MAGIC Imaging Atmospheric Cherenkov Telescope performed a follow-up
observation of the SWIFT/BAT burst GRB070920A (GCN circular 6805,
Grupe D., et al.). We received the GCN alert at T0+539s. The data taking
by MAGIC started at T0+690s, 2.5 minutes after the alert income.
We observed the sky positon for 36min spanning a zenith angle
in the range 53-50 degrees.
No evidence for VHE gamma-ray emission above the analysis threshold of
about 250 GeV was found. A preliminary analysis, taking advantage
for the first time of the fast 2GHz digitalization from the
new data acquisition system, and 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 efficiency):
E(225-300 GeV) : 7.1 x 10^(-8) erg/cm^2
E(300-400 GeV) : 4.6 x 10^(-8) erg/cm^2
E(400-1000 GeV) : 2.2 x 10^(-8) erg/cm^2
E(1-10 TeV) : 0.53 x 10^(-8) erg/cm^2
The upper limits correspond to the time period between T0+690s and
T0+2490s. We can also exclude emission of a constant flux during our observation
in any 100s time bin higher than:
E(225-300 GeV) : 1.9 x 10^(-7) erg/cm^2
E(300-400 GeV) : 1.0 x 10^(-7) erg/cm^2
E(400-1000 GeV) : 2.4 x 10^(-8) erg/cm^2
This message can be cited.
GCN Circular 6921
Subject
GRB 070920A: deep optical observations at the NOT
Date
2007-10-16T11:32:48Z (18 years ago)
From
Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center <malesani@astro.ku.dk>
A.O. Jaunsen (Univ. Oslo), J. Gorosabel (IAA-CSIC), J.P.U. Fynbo, D.
Malesani, J. Sollerman, Ch. Gall (DARK), T. Morel (Leuven), M.D.
Stritzinger (DARK), A. Somero, J. Telting, C. Villforth (NOT), report on
behalf of a larger collaboration:
We observed the field of GRB 070920A (Grupe et al., GCN #6805) in the R
band with the Nordic Optical Telescope on 2007 September 20.209-20.221
UT (1.0-1.3 hr after the GRB). Comparison images were taken on
September 20.216 and again on October 15.135 UT with the same
telescope, instrumentation and filter. Our images cover 96% of the
revised BAT error circle(Barbier et al., GCN #6807), missing a small
region at the northern boundary.
At a mean time of 1.15 hr after the GRB, we do not detect any
variable object brighter than R=24.3 (calibrated against USNO-B1.0, R1
magnitudes). There is no evidence for an associated SN on Oct. 15 down
to the same limit.