The History of GRB Outflows: Ejection Lorentz Factor and Radiation Location of X-Ray Flares

Mu, Hui-Jun; Lin, Da-Bin; Xi, Shao-Qiang; Lin, Ting‐Tse; Wang, Yuan-Zhu; Liang, Yun-Feng; Lu, Liying; Zhang, Jin; Liang, En‐Wei

doi:10.3847/0004-637x/831/1/111

Cited by 29 publications

(28 citation statements)

References 77 publications

(125 reference statements)

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“…There are several previous works taking into account the viewing angle effect on the observed flux (e.g., Yamazaki et al 2003). For most steep decay phases with strong spectral evolution, the value of β is the lowest at the beginning of the steep decay phase (e.g., Mu et al 2016;. If assumption (2) does not hold, the emitting region with the hardest intrinsic spectrum in the jet shell mayalways bein the direction of our sight.…”

Section: Procedures For Simulating Jet Emissionmentioning

confidence: 99%

“…Thus, it is believed that the steep decay phase may be the "tail" of the prompt emission (Barthelmy et al 2005b;Liang et al 2006;O'Brien et al 2006). The steep decay phase is also observed in the decay phase of flares (e.g., Jia et al 2016;Mu et al 2016;.…”

Section: Introductionmentioning

confidence: 99%

“…For a flare ( 116 s ) in GRB 131030A, the spectrum at the beginning of the steep decay phase can be fitted with a Band function. With the fitting result found in Mu et al (2016), i.e., 0.91 a = -, 3.19 b = -…”

Section: Testingmentioning

confidence: 99%

“…The strong evolution of spectral index β is always found in the steep decay phase (Butler & Kocevski 2007;Zhang et al 2007Zhang et al , 2009Starling et al 2008;Mu et al 2016). Several effects have been done to explain the strong β evolution in the scenario of the curvature effect.…”

Section: Introductionmentioning

confidence: 99%

“…Since photons observed later may be from the higher latitude angle (θ) of the jet shell, the softening spectrum may be due to a θ-dependent spectral shape in the comoving frame of the jet shell (Zhang et al 2007). In this scenario, the emitting region with the hardest spectrum in the jet shell should alwaysbein the direction of 0 q = for most steep decay phases with strong spectral evolution (e.g., Mu et al 2016). It seems to be contrived.…”

Section: Introductionmentioning

confidence: 99%

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Steep Decay Phase Shaped by the Curvature Effect. II. Spectral Evolution

Lin

Liang

et al. 2017

ApJ

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We derive a simple analytical formula to describe the evolution of spectral index β in the steep decay phase shaped by the curvature effect with theassumption that the spectral parameters and Lorentz factor of thejet shell arethe same for different latitudes. Here, the value of β is estimated in the 0.3−10 keV energy band. For a spherical thin shell with a cutoff power-law (CPL) intrinsic radiation spectrum, the spectral evolution can be read as a linear function of observer time. For the situation with theBand function intrinsic radiation spectrum, the spectral evolution may be complex. If the observed break energy of theradiation spectrum is larger than 10 keV, the spectral evolution is the same as that shaped by jet shells with a CPL spectrum. If the observed break energy is less than 0.3 keV, the value of β would be a constant. For others, the spectral evolution can be approximated as a logarithmal function of the observer time in general.

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Section: Procedures For Simulating Jet Emissionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Testingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Steep Decay Phase Shaped by the Curvature Effect. II. Spectral Evolution

Lin

Liang

et al. 2017

ApJ

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Spectral index-flux relation for investigating the origins of steep decay in γ-ray bursts

et al. 2021

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Abstractγ-ray bursts (GRBs) are short-lived transients releasing a large amount of energy (1051 − 1053 erg) in the keV-MeV energy range. GRBs are thought to originate from internal dissipation of the energy carried by ultra-relativistic jets launched by the remnant of a massive star’s death or a compact binary coalescence. While thousands of GRBs have been observed over the last thirty years, we still have an incomplete understanding of where and how the radiation is generated in the jet. Here we show a relation between the spectral index and the flux found by investigating the X-ray tails of bright GRB pulses via time-resolved spectral analysis. This relation is incompatible with the long standing scenario which invokes the delayed arrival of photons from high-latitude parts of the jet. While the alternative scenarios cannot be firmly excluded, the adiabatic cooling of the emitting particles is the most plausible explanation for the discovered relation, suggesting a proton-synchrotron origin of the GRB emission.

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Combined X-ray and optical analysis to probe the origin of the plateau emission in γ-ray burst afterglows

Ronchini¹,

Stratta²,

Rossi³

et al. 2023

A&A

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A large fraction of γ-ray bursts (GRBs) show a plateau phase during the X-ray afterglow emission, which has a physical origin that is still debated. In this work, we select a sample of 30 GRBs with simultaneous X-ray and optical data during and after the plateau phase. Through a time-resolved spectral analysis of the X-ray plateaus, we test the consistency of the unabsorbed optical fluxes with those obtained via X-ray-to-optical spectral extrapolation by assuming a synchrotron spectrum. By combining X-ray with optical data, we find that 63% (19/30) of GRBs are compatible with a single synchrotron spectrum, thus suggesting that both the optical and X-ray radiations are produced from a single emitting region. For these GRBs, we derive the temporal evolution of the break frequency, and we compare it with the expectations predicted by several models. For 11 of the 30 GRBs, the optical emission is above the predicted range of values extrapolated from the X-rays in at least one temporal bin of the light curve. These 11 GRBs may not be explained with a single-zone emission, indicating the necessity of invoking two co-operating processes in order to explain the broad-band spectral behaviour. We discuss our findings in the framework of different scenarios that are invoked to explain the plateau feature, including the energy injection from a spinning-down magnetar and the high latitude emission from a structured jet.

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The History of GRB Outflows: Ejection Lorentz Factor and Radiation Location of X-Ray Flares

Cited by 29 publications

References 77 publications

Steep Decay Phase Shaped by the Curvature Effect. II. Spectral Evolution

Steep Decay Phase Shaped by the Curvature Effect. II. Spectral Evolution

Spectral index-flux relation for investigating the origins of steep decay in γ-ray bursts

Combined X-ray and optical analysis to probe the origin of the plateau emission in γ-ray burst afterglows

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