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Global characteristics of GRBs observed with INTEGRAL and the inferred large population of low-luminosity GRBs
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
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2008 (English)In: Proc. Sci., 2008Conference paper (Refereed)
Abstract [en]

The g-ray instruments on board INTEGRAL have detected and localised 55 GRBs from launch in October 2002 up to July 2008, including 53 long-duration GRBs (T90 ≳ 2 s) and 2 short-duration GRBs (T90 ≲ 2 s). The spectra of the majority of INTEGRAL GRBs can be well described by single power-laws. In 11 cases, models with curvature, such as the Band model or the power law plus blackbody model, are required to fit the time-averaged burst spectra. INTEGRAL detects proportionally more weak GRBs than Swift because of its higher sensitivity in a smaller field of view. The all-sky rate of GRBs above ∼0.15phcm∼2 s-1 is ∼1400yr-1 in the fully coded field of view of IBIS. Spectral lags i.e. the time delay in the arrival of low-energy g-rays with respect to high-energy g-rays, can be measured for 31 of the GRBs in the sample. Two groups are identified in the spectral lag distribution of INTEGRAL GRBs, one with short lags <0.75 s (between 25-50 keV and 50-300 keV) and one with long lags > 0.75 s. Most of the long-lag GRBs are inferred to have low redshifts because of their tendency to have low peak energies and their faint optical and X-ray afterglows. They are mainly observed in the direction of the supergalactic plane with a quadrupole moment of Q = -0.225 ± 0.090 and hence reflect the local large-scale structure of the Universe. The rate of long-lag GRBs with inferred low luminosity is ∼25% of Type Ib/c SNe. Some of these bursts could be produced by the collapse of a massive star without a SN. Alternatively, they could result from a different progenitor, such as the merger of two white dwarfs or a white dwarf with a neutron star or black hole, possibly in the cluster environment without a host galaxy.

Place, publisher, year, edition, pages
, Proceedings of Science, ISSN 1824-8039
Keyword [en]
Cluster environments, Field of views, Large population, Large scale structure of the Universe, Massive stars, Quadrupole moments, Spectral lags, X-ray afterglow, Luminance, Stars
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-152182ScopusID: 2-s2.0-84883648598OAI: diva2:750777
7th INTEGRAL Workshop - An INTEGRAL View of Compact Objects, INTEGRAL 2008, 8-11 September 2008, Copenhagen, Denmark

QC 20140930

Available from: 2014-09-30 Created: 2014-09-23 Last updated: 2014-09-30Bibliographically approved

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