A Comprehensive Study of Multiflare GRB Spectral Lag

Abstract We select 48 multiflare gamma-ray bursts (GRBs) (including 137 flares) from the Swift/XRT database and estimate the spectral lag with the discrete correlation function. It is found that 89.8% of the flares have positive lags and only 9.5% of the flares show negative lags when fluctuations are taken into account. The median lag of the multiflares (2.75 s) is much greater than that of GRB pulses (0.18 s), which can be explained by the fact that we confirm that multiflare GRBs and multipulse GRBs have similar positive lag–duration correlations. We investigate the origin of the lags by checking the E peak evolution with the two brightest bursts and find the leading models cannot explain all of the multiflare lags and there may be other physical mechanisms. All of the results above reveal that X-ray flares have the same properties as GRB pulses, which further supports the observation that X-ray flares and GRB prompt-emission pulses have the same physical origin.

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Statistical Analyses of the Energies of X-Ray Plateaus and Flares in Gamma-Ray Bursts

The Astrophysical Journal ◽

10.3847/1538-4357/ac35e7 ◽

2022 ◽

Vol 924 (2) ◽

pp. 69

Author(s):

Shuang-Xi Yi ◽

Mei Du ◽

Tong Liu

Keyword(s):

Gamma Ray ◽

Gamma Ray Bursts ◽

Physical Origin ◽

Radiation Mechanisms ◽

Gaussian Distributions ◽

Emission Energy ◽

X Ray ◽

Central Engine ◽

Positive Correlations ◽

Prompt Emission

Abstract Distinct X-ray plateau and flare phases have been observed in the afterglows of gamma-ray bursts (GRBs), and most of them should be related to central engine activities. In this paper, we collect 174 GRBs with X-ray plateau phases and 106 GRBs with X-ray flares. There are 51 GRBs that overlap in the two selected samples. We analyze the distributions of the proportions of the plateau energy E plateau and the flare energy E flare relative to the isotropic prompt emission energy E γ,iso. The results indicate that they well meet the Gaussian distributions and the medians of the logarithmic ratios are ∼−0.96 and −1.39 in the two cases. Moreover, strong positive correlations between E plateau (or E flare ) and E γ,iso with slopes of ∼0.95 (or ∼0.80) are presented. For the overlapping sample, the slope is ∼0.80. We argue that most of X-ray plateaus and flares might have the same physical origin but appear with different features because of the different circumstances and radiation mechanisms. We also test the applicabilities of two models, i.e., black holes surrounded by fractured hyperaccretion disks and millisecond magnetars, on the origins of X-ray plateaus and flares.

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Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3090 ◽

2020 ◽

Vol 499 (4) ◽

pp. 5986-5992

Author(s):

Nikhil Sarin ◽

Paul D Lasky ◽

Gregory Ashton

Keyword(s):

Gravitational Wave ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Dipole Radiation ◽

X Ray ◽

Radiative Efficiency ◽

Central Engine ◽

Radiative Losses ◽

Wave Emission ◽

Prompt Emission

ABSTRACT The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin-down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin-down solely through vacuum dipole radiation. We find that our model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can further explain the diversity of X-ray plateaus by altering the radiative efficiency and measure the braking index of newly born millisecond magnetars. We measure the braking index of GRB061121 as $n=4.85^{+0.11}_{-0.15}$ suggesting the millisecond-magnetar born in this gamma-ray burst spins down predominantly through gravitational-wave emission.

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STOCHASTIC WAKEFIELD PLASMA ACCELERATION IN GAMMA-RAY BURSTS

International Journal of Modern Physics B ◽

10.1142/s0217979207042434 ◽

2007 ◽

Vol 21 (03n04) ◽

pp. 627-632

Author(s):

G. BARBIELLINI ◽

F. LONGO ◽

N. OMODEI ◽

D. GIULIETTI ◽

A. CELOTTI ◽

...

Keyword(s):

Particle Acceleration ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Low Energy ◽

Plasma Acceleration ◽

Gamma Ray Burst ◽

Initial Burst ◽

X Ray ◽

Wake Field ◽

Prompt Emission

Gamma-Ray Burst (GRB) prompt emission can, for specific conditions, be so powerful and short-pulsed to strongly influence any surrounding plasma. In this paper, we briefly discuss the possibility that a very intense initial burst of radiation produced by GRBs satisfy the intensity and temporal conditions to cause stochastic wake-field particle acceleration in a surrounding plasma of moderate density. We consider a simple but realistic GRB model for which particle wake-field acceleration can first be excited by a very strong low-energy precursor, and then be effective in producing the observed prompt X-ray and gamma-ray GRB emission.

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Gamma-ray bursts spectral correlations and their cosmological use

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2006.1976 ◽

2007 ◽

Vol 365 (1854) ◽

pp. 1385-1394 ◽

Cited By ~ 6

Author(s):

Giancarlo Ghirlanda

Keyword(s):

Gamma Ray ◽

Gamma Ray Bursts ◽

Spectral Energy ◽

Selection Effects ◽

Emission Energy ◽

X Ray ◽

New Class ◽

The Universe ◽

Prompt Emission ◽

Open Issues

The correlations involving the long-gamma-ray bursts (GRBs) prompt emission energy represent a new key to understand the GRB physics. These correlations have been proved to be the tool that makes long-GRBs a new class of standard candles. Gamma Ray Bursts, being very powerful cosmological sources detected in the hard X-ray band, represent a new tool to investigate the Universe in a redshift range, which is complementary to that covered by other cosmological probes (SNIa and CMB). A review of the , , and correlations is presented. Open issues related to these correlations (e.g. presence of outliers and selection effects) and to their use for cosmographic purposes (e.g. dependence on model assumptions) are discussed. Finally, the relevance of thermal components in GRB spectra is discussed in the light of some of the models recently proposed for the interpretation of the spectral-energy correlations.

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The late X-ray afterglow of gamma-ray bursts

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2006.1996 ◽

2007 ◽

Vol 365 (1854) ◽

pp. 1189-1195 ◽

Cited By ~ 3

Author(s):

Richard Willingale ◽

Paul T O'Brien

Keyword(s):

Gamma Ray ◽

Gamma Ray Bursts ◽

Spectral Indices ◽

Plateau Phase ◽

Start Time ◽

X Ray ◽

Temporal Decay ◽

Decay Parameters ◽

Steep Decay ◽

Prompt Emission

We have developed a functional fit which can be used to represent the entire temporal decay of the X-ray afterglow of gamma-ray bursts (GRBs). The fit delineates and parameterizes well-defined phases for the decay: the prompt emission; an initial steep decay; a shallow plateau phase; and finally, a powerlaw afterglow. For 20% of GRBs, the plateau phase is weak, or not seen, and the initial powerlaw decay becomes the final afterglow. We compare the temporal decay parameters and X-ray spectral indices for 107 GRBs discovered by Swift with the expectations of the standard fireball model including a search for possible jet breaks. For approximately 50% of GRBs, the observed afterglow is in accord with the model, but for the rest the temporal and spectral properties are not as expected. We identify a few possible jet breaks, but there are many examples where such breaks are predicted but are absent. We also find that the start time of the final afterglow decay, T a , is associated with the peak of the prompt γ -ray emission spectrum, E peak , just as optical jet-break times, t j , are associated with E peak in the Ghirlanda relation.

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Quark-Nova Explosion inside a Collapsar: Application to Gamma Ray Bursts

Advances in Astronomy ◽

10.1155/2009/463521 ◽

2009 ◽

Vol 2009 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Rachid Ouyed ◽

Denis Leahy ◽

Jan Staff ◽

Brian Niebergal

Keyword(s):

Gamma Ray ◽

Gamma Ray Bursts ◽

Prompt Gamma ◽

Stellar Envelope ◽

X Ray ◽

Star Forming ◽

Star Forming Regions ◽

Long Duration ◽

Model Features ◽

Prompt Emission

If a quark-nova occurs inside a collapsar, the interaction between the quark-nova ejecta (relativistic iron-rich chunks) and the collapsar envelope leads to features indicative of those observed in Gamma Ray Bursts. The quark-nova ejecta collides with the stellar envelope creating an outward moving cap (Γ∼1–10) above the polar funnel. Prompt gamma-ray burst emission from internal shocks in relativistic jets (following accretion onto the quark star) becomes visible after the cap becomes optically thin. Model features include (i) precursor activity (optical, X-ray,γ-ray), (ii) promptγ-ray emission, and (iii) afterglow emission. We discuss SN-less long duration GRBs, short hard GRBs (including association and nonassociation with star forming regions), dark GRBs, the energetic X-ray flares detected in Swift GRBs, and the near-simultaneous optical andγ-ray prompt emission observed in GRBs in the context of our model.

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Similar phenomena at different scales: black holes, the Sun, γ-ray bursts, supernovae, galaxies and galaxy clusters

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307009842 ◽

2006 ◽

Vol 2 (14) ◽

pp. 41-62 ◽

Cited By ~ 5

Author(s):

Shuang Nan Zhang

Keyword(s):

Black Holes ◽

Black Hole ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

The Sun ◽

Physical Processes ◽

X Ray ◽

Physical Mechanisms ◽

X Ray Binaries ◽

Fundamental Physical

AbstractMany similar phenomena occur in astrophysical systems with spatial and mass scales different by many orders of magnitudes. For examples, collimated outflows are produced from the Sun, proto-stellar systems, gamma-ray bursts, neutron star and black hole X-ray binaries, and supermassive black holes; various kinds of flares occur from the Sun, stellar coronae, X-ray binaries and active galactic nuclei; shocks and particle acceleration exist in supernova remnants, gamma-ray bursts, clusters of galaxies, etc. In this report I summarize briefly these phenomena and possible physical mechanisms responsible for them. I emphasize the importance of using the Sun as an astrophysical laboratory in studying these physical processes, especially the roles magnetic fields play in them; it is quite likely that magnetic activities dominate the fundamental physical processes in all of these systems.As a case study, I show that X-ray lightcurves from solar flares, black hole binaries and gamma-ray bursts exhibit a common scaling law of non-linear dynamical properties, over a dynamical range of several orders of magnitudes in intensities, implying that many basic X-ray emission nodes or elements are inter-connected over multi-scales. A future high timing and imaging resolution solar X-ray instrument, aimed at isolating and resolving the fundamental elements of solar X-ray lightcurves, may shed new lights onto the fundamental physical mechanisms, which are common in astrophysical systems with vastly different mass and spatial scales. Using the Sun as an astrophysical laboratory, “Applied Solar Astrophysics” will deepen our understanding of many important astrophysical problems.

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From the earliest pulses to the latest flares in long gamma-ray bursts

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732270 ◽

2018 ◽

Vol 615 ◽

pp. A80

Author(s):

A. Pescalli ◽

M. Ronchi ◽

G. Ghirlanda ◽

G. Ghisellini

Keyword(s):

Spectral Properties ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Peak Time ◽

Emission Pulse ◽

X Ray ◽

Temporal Properties ◽

Central Engine ◽

Prompt Emission ◽

Different Origin

The prompt emission of gamma-ray bursts extends from the early pulses observed in γ-rays (>15 keV) to very late flares of X-ray photons (0.3–10 keV). The duration of prompt γ-ray pulses is rather constant, while the width of X-ray flares correlates with their peak time, suggesting a possibly different origin. However, pulses and flares have similar spectral properties. Considering internal and external shock scenarios, we derive how the energy and duration of pulses scale with their time of occurrence, and we compare this with observations. The absence of an observed correlation between the prompt emission pulse duration and its time of occurrence favours an “internal” origin and confirms earlier results. We show that the energetic and temporal properties of X-ray flares are also consistent with being produced by internal shocks between slow fireballs with a small contrast between their bulk Lorentz factors. These results relax the requirement of a long-lasting central engine to explain the latest X-ray flares.

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