Gamma-ray bursts (GRBs) are short, highly energetic bursts of
gamma-ray photons (typically at sub-MeV) energies that originate
from cataclysmic explosions in the Universe, most likely associated
with the birth of stellar size black holes or rapidly spinning,
highly magnetized, neutron stars. During their brief episode of
emission (typically lasting tens of seconds), the total energy budget
reaches ~1051-1053 ergs, making them
one of the most powerful known
objects in the Universe. The gamma-ray spectra are non-thermal, with
most of the energy emitted as high energy photons. The spectra are
usually fitted by the smoothly connected low- and high-energy power
laws, with the peak of the emission at typically a few 100 keV. The
gamma-ray light curves show a wide variety, from smooth, fast rise and
exponential decay curves, through curves with several peaks, to highly
variable ones with many peaks.
The latest INTEGRAL catalogue of GRBs observed between December 2002 and
February 2012 contains the spectral information for 59 GRBs localized by
IBAS. For the spectral analysis, a new data extraction technique was applied,
which was developed in order to explore the energy ranges where both
instruments, SPI and IBIS, exhibit the highest sensitivity. It allowed to
analyze the GRB spectra over a broad energy range (20 keV - ~1 MeV) and to
determine the spectral peak energies. The light curves in the 20-200 keV
energy band were derived using IBIS data.
In the central part of the image the burst locations are shown. The size
of the symbols is proportional to burst durations, and the color code
corresponds to the peak flux (in photons/cm2/s) in the 20-200 keV energy
band. Several examples of the GRB light curves for long duration events are
shown, as well as a typical IBIS/SPI joint spectrum used in the spectral
analysis.
Reference:
"The spectral catalogue of INTEGRAL gamma-ray bursts: results of the joint
IBIS/SPI spectral analysis"
Ž. Bošnjak, D. Götz, L. Bouchet, S. Schanne, B. Cordier 2014, A&A, 561, id.A25
