Gamma-Ray Bursts from Minijets

Shaviv, Nir J.; Dar, Arnon

doi:10.1086/175923

Cited by 133 publications

(213 citation statements)

References 25 publications

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“…But various observations, including in particular the ones we shall extensively discuss here, strongly suggest that most of the long-duration GRBs are produced in supernova events (Dar & De Rújula 2000a and references therein) by highly collimated superluminal jets (e.g. Shaviv & Dar 1995;Dar 1997;Dar & Plaga 1999).…”

Section: Introductionmentioning

confidence: 89%

“…For N CB = 6 × 10 50 , γ = δ = 10 3 and z = 1, the above expression yields 1.5 × 10 −14 erg/(cm 2 s) for the CBR contribution, which is negligible relative to synchrotron radiation up to a very late afterglow phase, when n e may be very small. The contribution of Compton scattering to a polarization of the signals, on the other hand, may not be negligible (Shaviv & Dar 1995).…”

Section: Inverse Compton Scatteringmentioning

confidence: 99%

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On the optical and X-ray afterglows of gamma ray bursts

Dado

Dar

Rújula

2002

A&A

256

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Abstract. We severely criticize the consuetudinary analysis of the afterglows of gamma-ray bursts (GRBs) in the conical-ejection fireball scenarios. We argue that, instead, recent observations imply that the long-duration GRBs and their afterglows are produced by highly relativistic jets of cannonballs (CBs) emitted in supernova explosions. The CBs are heated by their collision with the supernova shell. The GRB is the boosted surface radiation the CBs emit as they reach the transparent outskirts of the shell. The exiting CBs further decelerate by sweeping up interstellar matter (ISM). The early X-ray afterglow is dominated by thermal bremsstrahlung from the cooling CBs, the optical afterglow by synchrotron radiation from the ISM electrons swept up by the CBs. We show that this model fits simply and remarkably well all the measured optical afterglows of the 15 GRBs with known redshift, including that of GRB 990123, for which unusually prompt data are available. We demonstrate that GRB 980425 was a normal GRB produced by SN1998bw, with standard X-ray and optical afterglows. We find that the very peculiar afterglow of GRB 970508 can be explained if its CBs encountered a significant jump in density as they moved through the ISM. The afterglows of the nearest 8 of the known-redshift GRBs show various degrees of evidence for an association with a supernova akin to SN1998bw. In all other cases such an association, even if present, would have been undetectable with the best current photometric sensitivities. This gives strong support to the proposition that most, maybe all, of the long-duration GRBs are associated with supernovae. Although our emphasis is on optical afterglows, we also provide an excellent description of X-ray afterglows.

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Section: Introductionmentioning

confidence: 89%

Section: Inverse Compton Scatteringmentioning

confidence: 99%

On the optical and X-ray afterglows of gamma ray bursts

Dado

Dar

Rújula

2002

A&A

256

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“…The subjet model might be compatible with the luminosityvariability relation that more complex bursts tend to be brighter Reichart et al 2001;Schaefer et al 2001). According to Plaga (2001), when the power density spectrum of the GRB time histories is (Belo- Stern, & Svensson 1998Shaviv & Dar 1995), the variability relates to the pulse width as priate offsets. The observed luminosity-variability relations for eight bursts with known redshifts are also plotted for comparison.…”

Section: Peak Luminosity-spectral Lag/variability Relationmentioning

confidence: 99%

“…X-ray-rich GRBs (Strohmayer et al 1998;Frontera et al 2000;Heise et al 2001;Kippen et al 2001) are also expected in the subjet model if none of the subjets point to our line of sight (Nakamura 2000). The subjet is sometimes called "cannonball" (Dar & De Rújula 2000Plaga 2001), "minijet" (Shaviv & Dar 1995), and so on.…”

mentioning

confidence: 99%

Peak Luminosity–Spectral Lag Relation Caused by the Viewing Angle of the Collimated Gamma-Ray Bursts

Ioka

Nakamura

2001

The Astrophysical Journal

169

207

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We compute the kinematical dependence of the peak luminosity, the pulse width, and the spectral lag of the peak luminosity on the viewing angle of a jet. For appropriate model parameters we obtain a peak luminosity-spectral v v lag relation similar to the observed one including gamma-ray burst (GRB) 980425. A bright (dim) peak with short (long) spectral lag corresponds to a jet with small (large) viewing angle. This suggests that the viewing angle of the jet might cause various relations in GRBs such as the peak luminosity-variability relation and the luminositywidth relation. Our model also suggests that X-ray-rich GRBs (or X-ray flushes or fast X-ray transients) are typical GRBs observed from large with large spectral lag and low variability.v v

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“…Shaviv & Dar 1995;Nakar et al 2003;Granot 2003;Lazzati et al 2004;Dado et al 2007). The RHESSI results highlighted the importance of correctly evaluating the systematic effects, which may mimic a polarisation signature.…”

Section: Introductionmentioning

confidence: 99%

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

McGlynn

Clark

Dean

et al. 2007

A&A

154

138

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Context. Linear polarisation in gamma-ray burst prompt emission is an important diagnostic with the potential to significantly constrain models. The spectrometer aboard INTEGRAL, SPI, has the capability to detect the signature of polarised emission from a bright γ-ray source. GRB 041219a is the most intense burst localised by INTEGRAL with a fluence of 5.7 ×10 −4 erg cm −2 over the energy range 20 keV-8 MeV and is an ideal candidate for such a study. Aims. Polarisation can be measured using multiple events scattered into adjacent detectors because the Compton scatter angle depends on the polarisation of the incoming photon. A search for linear polarisation in the most intense pulse of duration 66 seconds and in the brightest 12 seconds of GRB 041219a was performed in the 100-350 keV, 100-500 keV and 100 keV-1 MeV energy ranges. It was possible to divide the events into six directions in the energy ranges of 100-350 keV and 100-500 keV using the kinematics of the Compton scatter interactions. Methods. The multiple event data from the spectrometer was analysed and compared with the predicted instrument response obtained from Monte-Carlo simulations using the GEANT 4 INTEGRAL mass model. The χ 2 distribution between the real and simulated data as a function of the percentage polarisation and polarisation angle was calculated for all three energy ranges. The degree and angle of polarisation were obtained from the best-fit value of χ 2 . Results. A weak signal consistent with polarisation was found throughout the analyses. The degree of linear polarisation in the brightest pulse of duration 66 s was found to be 63 +31 −30 % at an angle of 70 +14 −11 degrees in the 100-350 keV energy range. The degree of polarisation was also constrained in the brightest 12 s of the GRB and a polarisation fraction of 96 +39 −40 % at an angle of 60 +12 −14 degrees was determined over the same energy range. However, despite extensive analysis and simulations, a systematic effect that could mimic the weak polarisation signal could not be definitively excluded. Conclusions. Our results over several energy ranges and time intervals are consistent with a polarisation signal of about 60% but at a low level of significance (∼2σ). The polarisation results are compared with predictions from the synchrotron and Compton drag processes. The spectrum of this GRB can also be well fit by a combined black body and power law model which could arise from a combination of the Compton and synchrotron processes, with different degrees of polarisation. We therefore conclude that the procedure described here demonstrates the effectiveness of using SPI as a polarimeter, and is a viable method of measuring polarisation levels in intense gamma-ray bursts.

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Gamma-Ray Bursts from Minijets

Cited by 133 publications

References 25 publications

On the optical and X-ray afterglows of gamma ray bursts

On the optical and X-ray afterglows of gamma ray bursts

Peak Luminosity–Spectral Lag Relation Caused by the Viewing Angle of the Collimated Gamma-Ray Bursts

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

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