Gamma-ray Bursts and Afterglow

The origin of GRBs has been a mystery for almost 30 years. Their sources emit a huge amount of energy on short time scales, and the process involves extreme relativistic motion with a bulk Lorentz factor of at least a few hundred. In the last two years, “afterglow” emission in X-ray, optical, IR, and radio was detected. The afterglow can be measured up to months and even years after the few-seconds GRB. We review the theories for the γ-ray emission and its afterglow, and show that these are strongly supported by observations. A recent detection of optical emission simultaneous with the GRB agrees well with theoretical predictions and further constrains the free parameters of the models. We discuss the evidence that some of the bursts are jets and discuss the prospects of polarization measurements.

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DISCERNING EMISSION COMPONENTS IN EARLY AFTERGLOW DATA AND CONSTRAINING THE INITIAL LORENTZ FACTOR OF LONG GRB FIREBALL

International Journal of Modern Physics D ◽

10.1142/s0218271811020007 ◽

2011 ◽

Vol 20 (10) ◽

pp. 1955-1959 ◽

Cited By ~ 1

Author(s):

EN-WEI LIANG ◽

HOUJUN LÜ ◽

SHUANG-XI YI ◽

BING ZHANG ◽

BIN-BIN ZHANG ◽

...

Keyword(s):

Gamma Ray ◽

Optical Emission ◽

Lorentz Factor ◽

Gamma Ray Bursts ◽

X Rays ◽

External Shocks ◽

X Ray ◽

Emission Component ◽

Power Law Decay ◽

Single Power

We prove that both the canonical and single power-law decay X-ray afterglow lightcurves of gamma-ray bursts (GRBs) observed with the Swift X-ray telescope may be an emission component radiated by external shocks prior to the GRB trigger. Our systematical analysis on both the early optical and X-ray afterglow data also indicates that they might be from different components. The detected optical emission possibly is dominated by the afterglow of the GRB fireball. The X-ray afterglows may be detected for some GRBs, but most of the detected X-rays for most GRBs are likely dominated by the prior X-ray component. With the deceleration feature in the early optical afterglow data, we estimate the initial Lorentz factors of the GRBs and discover a tight relation of the Lorentz factor to the isotropic gamma-ray energy.

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Gamma-ray-emitting narrow-line Seyfert 1 galaxies: the Swift view

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1580 ◽

2020 ◽

Vol 496 (2) ◽

pp. 2213-2229 ◽

Cited By ~ 1

Author(s):

F D’Ammando

Keyword(s):

Gamma Ray ◽

Thermal Emission ◽

Optical Emission ◽

X Rays ◽

Narrow Line ◽

X Ray ◽

Relativistic Jet ◽

Photon Index ◽

Γ Ray ◽

Lower Variability

ABSTRACT We report the analysis of all Swift observations available up to 2019 April of γ-ray-emitting narrow-line Seyfert 1 galaxies (NLSy1). The distribution of X-ray luminosities (and fluxes) indicates that the jet radiation significantly contributes to their X-ray emission, with Doppler boosting making values higher than other radio-loud NLSy1. The 0.3–10 keV photon indices are on average harder with respect to radio-quiet and radio-loud NLSy1, confirming a dominant jet contribution in X-rays. However, the lower variability amplitude with respect to blazars and the softening of the spectrum in some periods suggests that also the corona radiation contributes to the X-ray emission. In optical and ultraviolet (UV) significant flux changes have been observed on daily, weekly, and monthly time-scale, providing a clear indication of the significant contribution of the jet radiation in this part of spectrum. A strong correlation between X-ray, UV, and optical emission and simultaneous flux variations have been observed in 1H 0323+342, SBS 0846+513, PMN J0948+0022 as expected in case the jet radiation is the dominant mechanism. Correlated multiband variability favours the jet-dominated scenario also in FBQS J1644+2619 and PKS 2004−447. The summed X-ray Telescope spectra of 1H 0323+342, SBS 0846+513, PMN J0948+0022, and FBQS J1644+2619 are well fitted by a broken power law with a break around 2 keV. The spectrum above 2 keV is dominated by the non-thermal emission from a beamed relativistic jet, as suggested by the hard photon index. A Seyfert-like feature like the soft X-ray excess has been observed below 2 keV, making these γ-ray-emitting NLSy1 different from typical blazars.

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Exceptionally bright optical emission from a rare and distant gamma-ray burst

10.21203/rs.3.rs-1101440/v1 ◽

2021 ◽

Author(s):

Gor Oganesyan ◽

Sergey Karpov ◽

Martin Jelinek ◽

Gregory Beskin ◽

Samuele Ronchini ◽

...

Keyword(s):

Gamma Ray ◽

Massive Stars ◽

Optical Emission ◽

Gamma Ray Bursts ◽

Additional Component ◽

Relativistic Jets ◽

X Ray ◽

Forward Shock ◽

Multi Wavelength ◽

Wavelength Emission

Abstract Long gamma-ray bursts (GRBs) are produced by the dissipation of ultra-relativistic jets launched by newly-born black holes after the collapse of massive stars. Right after the luminous and highly variable gamma-ray emission, the multi-wavelength afterglow is released by the external dissipation of the jet in circumburst medium. We report the discovery of a very bright (10 mag) optical emission 28 s after the explosion of the extremely luminous and energetic GRB 210619B located at redshift 1.937. Early multi-filter observations allowed us to witness the end of the shock wave propagation into the GRB ejecta. We observed the spectral transition from a bright reverse to the forward shock emission, demonstrating that the early and late GRB multi-wavelength emission is originated from a very narrow jet propagating into an unusually rarefied interstellar medium. We also find evidence of an additional component of radiation, coming from the jet wings which is able explain the uncorrelated optical/X-ray emission.

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A compact X-ray emitting binary in likely association with 4FGL J0935.3+0901

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa655 ◽

2020 ◽

Vol 493 (4) ◽

pp. 4845-4851 ◽

Cited By ~ 1

Author(s):

Zhongxiang Wang ◽

Yi Xing ◽

Jujia Zhang ◽

Konstantina Boutsia ◽

Gege Wang ◽

...

Keyword(s):

Gamma Ray ◽

Optical Emission ◽

Emission Lines ◽

Large Area ◽

Time Resolved ◽

X Ray ◽

Current State ◽

Low Mass ◽

Γ Ray ◽

Error Circle

ABSTRACT 4FGL J0935.3+0901 is a γ-ray source detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope. We have conducted detailed analysis of the LAT data for this source and multiwavelength studies of the source field. Its γ-ray emission can be described with a power law (Γ = 2.0 ± 0.2) with an exponential cut-off (Ec = 2.9 ± 1.6 GeV), while the flux shows significant long-term variations. From analysis of archival Neil Gehrels Swift Observatory X-Ray Telescope data, we find only one X-ray source in the LAT’s 2σ error region. Within a $3.7\,{\rm arcsec}$ radius error circle of the X-ray source, there is only one optical object down to r′ ∼ 23 mag. Time-resolved photometry of the optical object indicates a likely 2.5 h periodic modulation, while its spectrum shows double-peaked hydrogen and helium emission lines (similar to those seen in accretion discs in low-mass X-ray binaries). Combining these results, we conclude that we have discovered a compact X-ray emitting binary in likely association with 4FGL J0935.3+0901, i.e. a millisecond pulsar (MSP) binary. We discuss the implication of the optical spectral features: this binary could be a transitional MSP system at a subluminous disc state, although the other possibility, the binary in a rotation-powered state showing the optical emission lines due to intrabinary interaction processes, cannot be excluded. Further observational studies will help to determine detailed properties of this candidate MSP binary and thus clarify its current state.

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The X-ray luminosity function of short gamma-ray bursts

Astrophysics and Space Science ◽

10.1007/s10509-021-03945-3 ◽

2021 ◽

Vol 366 (4) ◽

Author(s):

Zhi-Ying Liu ◽

Fu-Wen Zhang ◽

Si-Yuan Zhu

Keyword(s):

Luminosity Function ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

X Ray

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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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