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The catalog of GRBs localized by INTEGRAL

An international collaboration involving an IRAP engineer (Paul Sabatier University of Toulouse and CNRS) applied to the observation data of the INTEGRAL satellite, a new method of data extraction in order to draw up a catalog of gamma-ray bursts, then to perform their analysis on a wide range in energy. This study is the topic of an article published within the journal Astronomy & Atrophysics.

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 (1).

actu-integral1

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.

Notes :

(1) SPI et IBIS are the two main instruments of the INTEGRAL space observatory.

  • SPI (Spectrometer on INTEGRAL) is a spectrometer covering the energy range 20 keV-8 MeV
  • IBIS (Imager on Board INTEGRAL Satellite) is an "imager" operating between 15 keV and 10 MeV. 

The data from the two instruments are combined: IBIS is more sensitive to low energy (200 keV), while SPI is more sensitive to high energy (E> 200 keV).

Further Resources :

  • "The spectral catalogue of INTEGRAL gamma-ray bursts: results of the joint IBIS/SPI spectral analysis" par Ž. Bošnjak, D. Götz, L. Bouchet, S. Schanne, B. Cordier, 2014, A&A, 561, id.A25
  • ESA Press Release : http://www.rssd.esa.int/index.php?project=INTEGRAL&page=POM_generation&yr=2014&mon=05&extn=jpg

IRAP Contact :

Laurent Bouchet, laurent.bouchet@irap.omp.eu , Tel : 05 61 55 86 03

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