Gamma-ray bursts in the<b><i>Swift</i></b>era

Gehrels, N.; Cannizzo, J. K.; Norris, J. P.

doi:10.1088/1367-2630/9/2/037

Cited by 32 publications

(42 citation statements)

References 70 publications

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“…The best fit with a two-lognormal function gives the center values (T 90,p1 = 0.28 s and T 90,p2 = 42.83 s) and the widths (w 1 = 19.05 s and w 2 = 18.20 s) with the reduced Chi-square χ 2 /dof = 0.67, which are roughly consistent with those calculated from the BATSE data (McBreen et al 1994;Meegan et al 1996;Paciesas et al 1999;Horváth 2002;Nakar 2007). The superposed function has a minimum around 2 s as found by Kouveliotou et al (1993), indicating that the Swift sources are also divided into two classes, SGRBs and LGRBs, although the Swift is more sensitive to long soft bursts than the BATSE (Band 2006;Gehrels et al 2007). …”

Section: Observed T 90 Distributionsupporting

confidence: 84%

The duration properties of Swift Gamma-Ray Bursts

Zhang

Choi

2008

Proc. IAU

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Abstract.We report the systematic analysis of the durations for Swift gamma-ray bursts (GRBs) and compare the results with those of pre-Swift data. We show that the durations of Swift bursts also have two log-normal distributions that are clearly divided at T90 = 2 s. Their intrinsic durations also show a bimodal distribution but shift systematically toward the smaller value compared with the observed one. This study confirms the spectra of short GRBs are in general harder than the long GRBs and shows that this trend becomes weak in the source frame.

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Section: Observed T 90 Distributionsupporting

confidence: 84%

The duration properties of Swift Gamma-Ray Bursts

Zhang

Choi

2008

Proc. IAU

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“…The origin of long-soft bursts has been connected to the death of low-metallicity massive stars (Piran 2005;Gehrels et al 2007). However, while observations support a binary merger origin for short bursts (Nakar 2007;Gehrels et al 2007), the exact nature of the progenitor remains uncertain: they could be either double neutron stars (NS-NS) or black hole-neutron star (BH-NS) binaries. The number of BH-NS binaries that both merge and produce GRBs is hard to estimate since (i) no such system has yet been observed, (ii) formation models are rather uncertain and predict very small BH-NS merger rates (likely too small to explain most of the short bursts), and (iii) theory suggests that the fraction of BH-NS mergers producing bursts depends sensitively on the black hole spin and spin-orbit orientation (Belczynski et al 2008b), but black hole birth spins are not well constrained observationally or theoretically.…”

Section: Introductionmentioning

confidence: 99%

“…Such an observation would also indicate that if in fact short gamma-ray bursts are connected to neutron star mergers, the gamma-ray burst engine is best explained by the lesser known model invoking a highly magnetized massive neutron star. Subject headings: binaries: close -black hole physics -gravitational waves -stars: evolutionstars: neutron Online material: color figures Gamma-ray bursts (GRBs) have been separated into two classes: long-soft bursts and short bursts (Nakar 2007;Gehrels et al 2007). The origin of long-soft bursts has been connected to the death of low-metallicity massive stars (Piran 2005;Gehrels et al 2007).…”

mentioning

confidence: 99%

“…Subject headings: binaries: close -black hole physics -gravitational waves -stars: evolutionstars: neutron Online material: color figures Gamma-ray bursts (GRBs) have been separated into two classes: long-soft bursts and short bursts (Nakar 2007;Gehrels et al 2007). The origin of long-soft bursts has been connected to the death of low-metallicity massive stars (Piran 2005;Gehrels et al 2007). However, while observations support a binary merger origin for short bursts (Nakar 2007;Gehrels et al 2007), the exact nature of the progenitor remains uncertain: they could be either double neutron stars (NS-NS) or black hole-neutron star (BH-NS) binaries.…”

mentioning

confidence: 99%

“…Gamma-ray bursts (GRBs) have been separated into two classes: long-soft bursts and short bursts (Nakar 2007;Gehrels et al 2007). The origin of long-soft bursts has been connected to the death of low-metallicity massive stars (Piran 2005;Gehrels et al 2007).…”

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confidence: 99%

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The Lowest-Mass Stellar Black Holes: Catastrophic Death of Neutron Stars in Gamma-Ray Bursts

Belczyński

O’Shaughnessy

Kalogera³

et al. 2008

ApJ

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Mergers of double neutron stars are considered the most likely progenitors for short gamma-ray bursts. Indeed, such a merger can produce a black hole with a transient accreting torus of nuclear matter, and the conversion of a fraction of the torus mass-energy to radiation can power a gamma-ray burst. Using available binary pulsar observations supported by our extensive evolutionary calculations of double neutron star formation, we demonstrate that the fraction of mergers that can form a black hole-torus system depends very sensitively on the (largely unknown) maximum neutron star mass. We show that the available observations and models put a very stringent constraint on this maximum mass under the assumption that black hole formation is required to produce a short gamma-ray burst in a double neutron star merger. Specifically, we find that the maximum neutron star mass must be within . Moreover, a single unambiguous measurement of a neutron star mass above 2-2.5 M , would exclude a black hole-torus central engine model of short gamma-ray bursts in double neutron 2.5 M , star mergers. Such an observation would also indicate that if in fact short gamma-ray bursts are connected to neutron star mergers, the gamma-ray burst engine is best explained by the lesser known model invoking a highly magnetized massive neutron star. Subject headings: binaries: close -black hole physics -gravitational waves -stars: evolutionstars: neutron Online material: color figures Gamma-ray bursts (GRBs) have been separated into two classes: long-soft bursts and short bursts (Nakar 2007;Gehrels et al. 2007). The origin of long-soft bursts has been connected to the death of low-metallicity massive stars (Piran 2005;Gehrels et al. 2007). However, while observations support a binary merger origin for short bursts (Nakar 2007;Gehrels et al. 2007), the exact nature of the progenitor remains uncertain: they could be either double neutron stars (NS-NS) or black hole-neutron star (BH-NS) binaries. The number of BH-NS binaries that both merge and produce GRBs is hard to estimate since (i) no such system has yet been observed, (ii) formation models are rather uncertain and predict very small BH-NS merger rates (likely too small to explain most of the short bursts), and (iii) theory suggests that the fraction of BH-NS mergers producing bursts depends sensitively on the black hole spin and spin-orbit orientation (Belczynski et al. 2008b), but black hole birth spins are not well constrained observationally or theoretically. On the other hand, NS-NS binaries are observed only in the Milky Way, but their properties and numbers are also in agreement with theoretical models, and their merger rate is sufficient to explain the present-day short-burst population (Nakar 2007;Belczynski et al. 2007).We have performed an extensive theoretical study of highmass binary stars (potential progenitors of NS-NS systems) using StarTrack, a population synthesis code incorporating the most up-to-date and detailed input physics for massive stars (Belczynski et al. ...

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Statistical study of observed and intrinsic durations among BATSE and Swift/BAT GRBs

Zitouni

Guessoum

Azzam

et al. 2015

Astrophys Space Sci

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Studies of BATSE bursts (Kouveliotou et al. 1993) have resulted in the widespread adoption of a two-group categorization: long bursts (those with durations ≥ 2 seconds) and short bursts (those with durations ≤ 2 seconds). This categorization, one must recall, used the observed T 90 time durations for bursts (during which 90% of a burst's fluence is measured).In this work, we have explored two ideas: 1) a statistical search for a possible third, intermediate category of bursts (between the "short" and the "long" ones) among 2041 BATSE GRBs and 757 Swift/BAT ones; 2) a study of bursts' intrinsic durations, where durations in the bursts' reference frames (instead of the observed durations) are considered; for this, 248 Swift/BAT bursts that have redshift measurements were statistically analyzed for the same categorization goal.We first use a Monte Carlo method to determine the proper binning of each GRB, considering that bursts come with different uncertainties on their durations. Then, using the method of minimization of chi-square χ 2 , we search for the best fit of the normalized frequency distributions 1 N0 dN d ln T of durations; this allows us to compare fits with two groups ("short" and "long") with fits with three groups ("short", "long", and "intermediate").Our results indicate that the distributions of observed durations are better fitted by three groups than two groups for Swift/BAT data; interestingly, the "intermediate" group appears rather clearly for both observed and intrinsic durations. For BATSE data, the statistical test does not prefer three groups over two.We discuss the results, their possible underlying causes, and reasonable interpretations.

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Gamma-ray bursts in theSwiftera

Cited by 32 publications

References 70 publications

The duration properties of Swift Gamma-Ray Bursts

The duration properties of Swift Gamma-Ray Bursts

The Lowest-Mass Stellar Black Holes: Catastrophic Death of Neutron Stars in Gamma-Ray Bursts

Statistical study of observed and intrinsic durations among BATSE and Swift/BAT GRBs

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