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Spectral lags of GRBs observed with INTEGRAL and the inferred large population of low-luminosity GRBs
KTH, School of Engineering Sciences (SCI), Physics.
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2009 (English)In: Gamma-ray bursts, American Institute of Physics (AIP), 2009, 362-367 p.Conference paper (Refereed)
Abstract [en]

The γ-ray instruments on board INTEGRAL detected and localised 47 GRBs from its launch in October 2002 up to July 2007. The peak flux distribution shows that 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 ∼0.15ph cm 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 γ-rays with respect to high-energy γ-rays, are measured for 31 of the GRBs. 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 long spectral lags, 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
American Institute of Physics (AIP), 2009. 362-367 p.
, AIP Conference Proceedings, ISSN 0094-243X ; 1133
Keyword [en]
Gamma-rays: bursts
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-153516DOI: 10.1063/1.3155919ISI: 000267717300084ScopusID: 2-s2.0-70450160005ISBN: 978-073540670-4OAI: diva2:758037
6th Huntsville Symposium on Gamma-Ray Bursts, 20 October 2008 through 23 October 2008, Huntsville, AL, United States

QC 20141024

Available from: 2014-10-24 Created: 2014-10-06 Last updated: 2014-10-24Bibliographically approved

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McGlynn, Sinéad
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Astronomy, Astrophysics and Cosmology

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