IBIS/PICsIT detects high energy prompt emission from Gamma Ray Bursts
Gamma Ray Bursts (GRB) are extreme powerful cosmic phenomena, being observed
in a wide range of light-curve shapes and durations, as well as energetic
spectral properties. Their origin is thought to be related to dramatic episodes
of collapse of massive stars (for long events) or compact objects within binary
systems (for short events), however the underlying physical processes are still
not fully understood. Direct observation of the prompt emission at high energy
is therefore of importance.
During the time period from March 2003 until December 2006, after having analyzed
data from 56 revolutions, eleven GRB events have been positively detected by the
PICsIT instrument aboard the INTEGRAL satellite, the high energy (~300 keV to
~ 3 MeV) detector of the IBIS telescope. PICSiT represents an important tool to
explore the prompt emission from GRBs at high energies. With its Spectral Timing
acquisition mode, IBIS/PICsIT allows a time resolution down to 1 ms, while
keeping spectral information in up to 8 energy channels, from 208 to 2600 keV.
On March 20th 2003, IBIS/PICsIT registered the peculiar light curves shown here
in two energy channels and rebinned at 0.5 seconds. Two GRB trigger events are
present. The first event shows a double-peaked structure, with the two peaks
being separated by about 40 seconds, and it has been identified with GRB 030320.
This GRB was also observed by SPI-ACS and IBIS/ISGRI (e.g. see von Kienlin et
al. 2003; Vianello et al. 2009). The second event, detected approximately
500 seconds after the first one, has not been identified yet and its origin
remains unclear, since spatial information or documented position has not been
provided by other instruments/observatories.
This result confirms the importance of a spectrally-resolved timing analysis for
the study of GRB up to several hundreds of keV, and the significant contribution
that IBIS/PICsIT is giving in this field.
The updated spectral catalogue of INTEGRAL gamma-ray bursts.
Vianello G., Goetz D., Mereghetti S., 2009, A&A, 495, 1005
http://arxiv.org/abs/0812.3349
INTEGRAL results on GRB 030320: A long gamma-ray burst detected at the edge of the field of view.
von Kienlin A., Beckmann V., Covino S., et al., 2003, A&A 411,L321
http://adsabs.harvard.edu/abs/2003A%26A...411L.321V
