The afterglow of a relativistic shock breakout and low-luminosity GRBs

Duran, R. Barniol; Nakar, Ehud; Piran, Tsvi; Sari, Re’em

doi:10.1093/mnras/stv011

Cited by 44 publications

(57 citation statements)

References 69 publications

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“…This model also helps to explain the lack of a jet break in the radio, since the jet outflow becomes quasi-spherical before leaving the envelope. A wind-like CSM profile is also inferred for afterglows powered by shock breakout (Barniol Duran et al 2015), which is expected for a WR star progenitor. On the other hand, the high value (∼ 50 keV) and slow decay (∝ t −(0.5−1) ) of the prompt peak energy that one expects in the shock breakout scenario (Nakar & Sari 2012) seem hard to reconcile with direct measurements of the peak energy that show it declines steeply as t −1.6 and with a value of ∼ a few keV throughout most of the prompt phase (Toma et al 2007).…”

Section: Discussionmentioning

confidence: 54%

“…The advantage of their view is that it eliminates the efficiency problem, as the isotropic equivalent kinetic energy during the early beamed phase is larger by a factor 2/θ 2 0 . Barniol Duran et al (2015) also looked at a mildly relativistic synchrotron model in the context of SN shock breakout. In this case, the light curve decays more slowly since energy is continuously injected as the outer layers of the SN ejecta catch up to the shocked region.…”

Section: Radio Afterglowmentioning

confidence: 99%

“…In practice, this is typically addressed by fixing two of the parameters to obtain the other two. (For example, Soderberg et al (2006) Barniol Duran et al (2015) fix e and E k .) We take a different approach.…”

Section: Radio Afterglowmentioning

confidence: 99%

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Jet or shock breakout? The low-luminosity GRB 060218

Irwin

Chevalier

2016

Mon. Not. R. Astron. Soc.

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We consider a model for the low-luminosity gamma-ray burst GRB 060218 that plausibly accounts for multiwavelength observations to day 20. The model components are: (1) a long-lived (t j ∼ 3000 s) central engine and accompanying low-luminosity (L j ∼ 10 47 erg s −1 ), semirelativistic (γ ∼ 10) jet; (2) a low-mass (∼ 4 × 10 −3 M ) envelope surrounding the progenitor star; and (3) a modest amount of dust (A V ∼ 0.1 mag) in the interstellar environment. Blackbody emission from the transparency radius in a low-power jet outflow can fit the prompt thermal X-ray emission, and the nonthermal X-rays and γ-rays may be produced via Compton scattering of thermal photons from hot leptons in the jet interior or the external shocks. The later mildly relativistic phase of this outflow can produce the radio emission via synchrotron radiation from the forward shock. Meanwhile, interaction of the associated SN 2006aj with a circumstellar envelope extending to ∼ 10 13 cm can explain the early optical emission. The X-ray afterglow can be interpreted as a light echo of the prompt emission from dust at ∼ 30 pc. Our model is a plausible alternative to that of Nakar, who recently proposed shock breakout of a jet smothered by an extended envelope as the source of prompt emission. Both our results and Nakar's suggest that bursts such as GRB 060218 may originate from unusual progenitors with extended circumstellar envelopes, and that a jet is necessary to decouple the prompt emission from the supernova.

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Section: Discussionmentioning

confidence: 54%

Section: Radio Afterglowmentioning

confidence: 99%

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Jet or shock breakout? The low-luminosity GRB 060218

Irwin

Chevalier

2016

Mon. Not. R. Astron. Soc.

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“…Based on the smooth light curve and long engine duration, they posited a neutron star-powered rather than black hole-powered central engine. Barniol Duran et al (2015) calculated the synchrotron afterglow light curves from a relativistic shock breakout, and while their model could fit the radio emission of GRB 060218, it predicted too low a flux and too shallow a temporal decay for the X-ray afterglow. Margutti et al (2015) analyzed the X-ray afterglows of 12 nearby GRBs and established that GRB 060218 and GRB 100316D belong to a distinct subgroup marked by long duration, soft-photon index, and high absorption.…”

Section: Introductionmentioning

confidence: 99%

“…The prompt X-rays are produced by the shock breaking out of the optically thick envelope (as described in Nakar & Sari 2012), and optical radiation is emitted as the envelope expands and cools (as in Nakar & Piro 2014). Interaction of the breakout ejecta with circumstellar material (CSM) generates the radio via synchrotron radiation (as in Barniol Duran et al 2015). Nakar's model does not, however, attempt to explain the unusual X-ray afterglow or the presence of thermal X-rays at early times.…”

Section: Introductionmentioning

confidence: 99%

Long-Duration, Low-Luminosity Gamma-Ray Bursts: Towards a Comprehensive Model of the Weakest Engine-Driven Explosions

Irwin¹

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Long-duration, low-luminosity gamma-ray bursts (LLGRBs) are a peculiar subclass of gamma-ray bursts (GRBs) that are up to 5 orders of magnitude less luminous than typical bursts. The observation of Type Ic supernovae (SNe) accompanying LLGRBs supports the notion that, like typical GRBs, they are powered by the gravitational collapse of a massive star's core, but beyond this little is known about their origin, and the differences between the progenitors of LLGRBs and GRBs are unclear.In this dissertation, I present analytical and numerical modeling that aims to improve our understanding of the physical conditions leading to LLGRBs.We consider first the unusual GRB 060218, a well-studied event that is prototypical of the long-duration LLGRB class. We present a model for this burst that can account for the prompt X-ray emission lasting for ∼ 3000 s, the early optical peak lasting for hours, and the X-ray and radio afterglow lasting for several days.The basic ingredients of the model are a long-lived jet (t j ∼ 3000 s) with an unusually low luminosity (L j ∼ 10 47 erg s −1 ), a progenitor star surrounded by an extended (∼ 10 13 cm), optically thick, low-mass (∼ 10 −2 M ) envelope, and a modest amount of dust (A V ∼ 0.1) in the interstellar environment.We fit the observed thermal component of the prompt X-ray emission with a simple photospheric model, and then calculate the nonthermal emission due to inverseCompton (IC) scattering of thermal photons from the external shocks of the jet. We find that this model can fit the observed nonthermal emission, if the conditions are such that the reverse shock dominates the emission. We show that the low-power jet can successfully traverse the progenitor star and extended envelope, and that it can also produce the observed radio emission via external shock synchrotron emission at late times. In the meantime, fast ejecta from the associated SN 2006aj shock the iii extended envelope, which emits a burst of optical emission as it expands and cools, consistent with the early optical peak. We interpret the anomalous X-ray afterglow in GRB 060218 as a light echo from dust situated ∼ 30 pc from the burst. Our results suggest that LLGRB progenitors are shrouded in dense circumstellar envelopes, and that they require both a jet and a supernova. Support for this view comes fromNakar (2015), who considered a different model for LLGRBs involving choked jets, but arrived at the same main conclusions.Motivated by these results, we also perform numerical simulations of jets with standard GRB properties in stars with extended envelopes. We present analytical calculations that predict whether or not the jet escapes successfully from the envelope, and apply them to interpret the numerical results. We find that the jet-driven outflow is more well-confined by the envelope than previous analytical results suggested, leading to a flow that is far from spherically symmetric when it breaks out of the envelope. This is generally true for a wide range of physical parameters. Even though the outf...

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Thermal and Nonthermal Emission from Circumstellar Interaction

Chevalier¹,

Fransson²

2017

Handbook of Supernovae

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It has become clear during the last decades that the interaction between the supernova ejecta and the circumstellar medium is playing a major role both for the observational properties of the supernova and for understanding the evolution of the progenitor star leading up to the explosion. In addition, it provides an opportunity to understand the shock physics connected to both thermal and non-thermal processes, including relativistic particle acceleration, radiation processes and the hydrodynamics of shock waves. This chapter has an emphasis on the information we can get from radio and X-ray observations, but also their connection to observations in the optical and ultraviolet. We first review the different physical processes involved in circumstellar interaction, including hydrodynamics, thermal X-ray emission, acceleration of relativistic particles and non-emission processes in the radio and X-ray ranges. Finally, we discuss applications of these to different types of supernovae.

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The afterglow of a relativistic shock breakout and low-luminosity GRBs

Cited by 44 publications

References 69 publications

Jet or shock breakout? The low-luminosity GRB 060218

Jet or shock breakout? The low-luminosity GRB 060218

Long-Duration, Low-Luminosity Gamma-Ray Bursts: Towards a Comprehensive Model of the Weakest Engine-Driven Explosions

Thermal and Nonthermal Emission from Circumstellar Interaction

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