scholarly journals Structured, relativistic jets driven by radiation

2020 ◽  
Vol 499 (3) ◽  
pp. 3158-3177 ◽  
Author(s):  
Eric R Coughlin ◽  
Mitchell C Begelman
Keyword(s):  
Fast Moving ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Dynamical Evolution ◽  
Compact Object ◽  
Lorentz Factor ◽  
Radiation Hydrodynamics ◽  
Relativistic Jets ◽  
Radiative Processes ◽  
Jet Structure

ABSTRACT Relativistic jets, or highly collimated and fast-moving outflows, are endemic to many astrophysical phenomena. The jets produced by gamma-ray bursts (GRBs) and tidal disruption events (TDEs) are accompanied by the accretion of material on to a black hole or neutron star, with the accretion rate exceeding the Eddington limit of the compact object by orders of magnitude. In such systems, radiation dominates the energy–momentum budget of the outflow, and the dynamical evolution of the jet is governed by the equations of radiation hydrodynamics. Here, we show that there are analytical solutions to the equations of radiation hydrodynamics in the viscous (i.e. diffusive) regime that describe structured, relativistic jets, which consist of a fast-moving, highly relativistic core surrounded by a slower moving, less relativistic sheath. In these solutions, the slower moving, outer sheath contains most of the mass, and the jet structure is mediated by local anisotropies in the radiation field. We show that, depending on the pressure and density profile of the ambient medium, the angular profile of the jet Lorentz factor is Gaussian or falls off even more steeply with angle. These solutions have implications for the nature of jet production and evolution in hyperaccreting systems, and demonstrate that such jets – and the corresponding jet structure – can be sustained entirely by radiative processes. We discuss the implications of these findings in the context of jetted TDEs and short and long GRBs.

scholarly journals The dynamic ejecta of compact object mergers and eccentric collisions

2013 ◽  
Vol 371 (1992) ◽  
pp. 20120272 ◽  
Author(s):  
Stephan Rosswog
Keyword(s):  
Globular Clusters ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Compact Object ◽  
Solar Mass ◽  
Abundance Pattern ◽  
Compact Binary ◽  
Hydrodynamical Simulations ◽  
Rich Material ◽  
R Process

Compact object mergers eject neutron-rich matter in a number of ways: by the dynamical ejection mediated by gravitational torques, as neutrino-driven winds, and probably also a good fraction of the resulting accretion disc finally becomes unbound by a combination of viscous and nuclear processes. If compact binary mergers indeed produce gamma-ray bursts, there should also be an interaction region where an ultra-relativistic outflow interacts with the neutrino-driven wind and produces moderately relativistic ejecta. Each type of ejecta has different physical properties, and therefore plays a different role for nucleosynthesis and for the electromagnetic (EM) transients that go along with compact object encounters. Here, we focus on the dynamic ejecta and present results for over 30 hydrodynamical simulations of both gravitational wave-driven mergers and parabolic encounters as they may occur in globular clusters. We find that mergers eject approximately 1 per cent of a Solar mass of extremely neutron-rich material. The exact amount, as well as the ejection velocity, depends on the involved masses with asymmetric systems ejecting more material at higher velocities. This material undergoes a robust r-process and both ejecta amount and abundance pattern are consistent with neutron star mergers being a major source of the ‘heavy’ ( A >130) r-process isotopes. Parabolic collisions, especially those between neutron stars and black holes, eject substantially larger amounts of mass, and therefore cannot occur frequently without overproducing gala- ctic r-process matter. We also discuss the EM transients that are powered by radioactive decays within the ejecta (‘macronovae’), and the radio flares that emerge when the ejecta dissipate their large kinetic energies in the ambient medium.

scholarly journals SIMULATION OF RELATIVISTIC JETS AND ASSOCIATED SELF-CONSISTENT RADIATION

2012 ◽  
Vol 08 ◽  
pp. 259-264 ◽  
Author(s):  
K.-I. NISHIKAWA ◽  
J. NIEMIEC ◽  
B. ZHANG ◽  
M. MEDVEDEV ◽  
P. HARDEE ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Lorentz Factor ◽  
Shock Structure ◽  
Spectral Structure ◽  
Relativistic Jets ◽  
Collisionless Shocks ◽  
Electron Positron ◽  
Transverse Deflection

Plasma instabilities are responsible not only for the onset and mediation of collisionless shocks but also for the associated acceleration of particles. We have investigated particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electrons transverse deflection and, more generally, relativistic acceleration behind the shock. We have calculated, self-consistently, the radiation from electrons accelerated in the turbulent magnetic fields. We found that the synthetic spectra depend on the Lorentz factor of the jet, its thermal temperature and strength of the generated magnetic fields. The properties of the radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants.

VACUUM DISCHARGE AS A POSSIBLE SOURCE OF GAMMA-RAY BURSTS

2000 ◽  
Vol 09 (02) ◽  
pp. 185-192
Author(s):  
G. MAO ◽  
S. CHIBA ◽  
W. GREINER ◽  
K. OYAMATSU
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Critical Density ◽  
Compact Object ◽  
Dense Matter ◽  
Initial Energy ◽  
Strong Interactions ◽  
Γ Ray ◽  
The Impact

We propose that spontaneous particle–anti-particle pair creations from the discharged vacuum caused by the strong interactions in dense matter are major sources of γ-ray bursts. Two neutron star collisions or black-hole-neutron star mergers at cosmological distance could produce a compact object with its density exceeding the critical density for pair creations. The emitted anti-particles annihilate with corresponding particles at the ambient medium. This releases a large amount of energy. We discuss the spontaneous [Formula: see text] pair creations within two neutron star collision and estimate the exploded energy from [Formula: see text] annihilation processes. The total energy could be around 1051–1053 erg depending on the impact parameter of colliding neutron stars. This value fits well into the range of the initial energy of the most energetic γ-ray bursts.

scholarly journals Afterglow light curves from misaligned structured jets

2020 ◽  
Vol 493 (3) ◽  
pp. 3521-3534 ◽  
Author(s):  
Paz Beniamini ◽  
Jonathan Granot ◽  
Ramandeep Gill
Keyword(s):  
Light Curve ◽  
Gamma Ray ◽  
Lorentz Factor ◽  
Light Curves ◽  
Opening Angle ◽  
Model Parameters ◽  
Narrow Strip ◽  
Double Peaks ◽  
Wide Range ◽  
Jet Structure

ABSTRACT GRB 170817A/GW 170817 is the first gamma-ray burst (GRB) clearly viewed far from the GRB jet’s symmetry axis. Its afterglow was densely monitored over a wide range of frequencies and times. It has been modelled extensively, primarily numerically, and although this endeavour was very fruitful, many of the underlying model parameters remain undetermined. We provide analytic modelling of GRB afterglows observed off-axis, considering jets with a narrow core (of half-opening angle θc) and power-law wings in energy per unit solid angle (ϵ = ϵcΘ−a where Θ = [1 + (θ/θc)2]1/2) and initial specific kinetic energy (Γ0 − 1 = [Γc, 0 − 1]Θ−b), as well as briefly discuss Gaussian jets. Our study reveals qualitatively different types of light curves that can be viewed in future off-axis GRBs, with either single or double peaks, depending on the jet structure and the viewing angle. Considering the light-curve shape rather than the absolute normalizations of times and/or fluxes, removes the dependence of the light curve on many of the highly degenerate burst parameters. This study can be easily used to determine the underlying jet structure, significantly reduce the effective parameter space for numerical fitting attempts and provide physical insights. As an illustration, we show that for GRB 170817A, there is a strong correlation between the allowed values of Γc, 0 and b, leading to a narrow strip of allowed solutions in the Γc, 0–b plane above some minimal values Γc, 0 ≳ 40, b ≳ 1.2. Furthermore, the Lorentz factor of the material dominating the early light curve can be constrained by three independent techniques to be Γ0(θmin, 0) ≈ 5–7.

scholarly journals Lorentz Factor Evolution Patterns within Relativistic Jets of GRBs and AGNs

2016 ◽  
Vol 12 (S324) ◽  
pp. 78-81
Author(s):  
Hai-Ming Zhang ◽  
Da-Bin Lin ◽  
Ting-Ting Lin ◽  
Bao-Rong Liu ◽  
Xiao-Li Huang ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Empirical Relation ◽  
Lorentz Factor ◽  
Jet Physics ◽  
Spectral Energy ◽  
Relativistic Jets ◽  
Evolution Pattern ◽  
Relativistic Jet ◽  
Γ Ray

AbstractThe Lorentz factor (Γ) is an important parameter related to the relativistic jet physics. We study the evolution patterns of Γ within gamma-ray burst (GRB) and active galactic nuclear jets for individual GRB 090168, GRB 140508A, and 3C 454.3. By estimating the Γ values for well-separated pulses in GRBs 090618 and 140508A with an empirical relation derived from typical GRBs, we find that the Γ evolution pattern in the two GRBs are different. The increasing-to-coasting evolution pattern of Γ in GRB 090618 likely indicates that the GRB fireball is still being accelerated in the prompt phase. The clear decrease evolution pattern of Γ in GRB 140508A suggests the deceleration of the fireball components. By deriving the Γ value through fitting their spectral energy distribution in different flares of 3C 454.3, a pattern of Γ-tracking-γ-ray flux is clearly found, likely indicating that the observed gamma-ray flares are being due to the Doppler boosting effect to the jet emission.

scholarly journals Non-thermal emission produced by the interaction of a jet with a supernova remnant

2018 ◽  
Vol 27 (10) ◽  
pp. 1844021
Author(s):  
F. L. Vieyro ◽  
V. Bosch-Ramon ◽  
N. Torres-Albà
Keyword(s):  
Supernova Remnant ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Dynamical Evolution ◽  
Lorentz Factor ◽  
Starburst Galaxy ◽  
Core Collapse ◽  
Relativistic Jet ◽  
Relativistic Regime ◽  
Gamma Ray Emission

Core-collapse supernovae (SNe) are found in galaxies with ongoing star-formation. If a starburst galaxy hosts an active galactic nucleus (AGN) with a relativistic jet, the SN could take place inside the jet. The collision of the SN ejecta with the jet flow leads to the formation of a shock, where particles could be accelerated up to relativistic energies, and produce gamma-ray emission. In this work, we analyze the dynamical evolution of the SN within the jet, and compute the non-thermal radiation expected from the interaction. The evolution of the SN Lorentz factor and radius regulates the intensity of the non-thermal emission. The SN can achieve a relativistic regime for powerful jets, resulting in emission significantly enhanced by Doppler boosting for blazar sources. The interaction of SNe with jets of moderate luminosity can result in steady, unbeamed gamma-ray emission, that might be detectable for sources in the local universe.

scholarly journals Possible evidence of a supermassive black hole binary with two radio jets in blazar 3C279

2018 ◽  
Vol 621 ◽  
pp. A11 ◽  
Author(s):  
S. J. Qian ◽  
S. Britzen ◽  
T. P. Krichbaum ◽  
A. Witzel
Keyword(s):  
Black Hole ◽  
Complex Structure ◽  
Lorentz Factor ◽  
Electromagnetic Spectrum ◽  
Apparent Velocity ◽  
Relativistic Jets ◽  
Supermassive Black Hole ◽  
Black Hole Binary ◽  
Jet Structure ◽  
Two Jets

Context. Studies of periodic and quasi-periodic phenomena in optical and radio bands are important for understanding the physical processes in quasars. Investigation of periodic/quasi-periodic behavior of the relativistic jets in blazars is particularly significant because it can provide unique information about the formation, collimation, and acceleration of the jets and the properties of the central engines (black hole/accretion disk systems) in blazars. Aims. We investigate the parsec-scale kinematics of the 31 superluminal components observed in blazar 3C279 and attempt to search for evidence of its jet precession and double-jet structure. Methods. The previously suggested precessing jet nozzle model is applied to model-fit the kinematics of its superluminal components observed during the 1981–2015 period. It is shown that the parsec-scale kinematics of the entire source can be interpreted in terms of a double-jet scenario. Results. The superluminal components observed in 3C279 can be divided into two groups that are ejected from two relativistic jets. The two jets have different orientations in space and jet-cone shapes, but both jets precess with the same precession period of 25 yr (16.3 yr in the source frame). The kinematic features of all the superluminal knots (trajectory, core separation, and apparent velocity) can be consistently explained. Their innermost trajectories follow the respective precessing common parabolic patterns with trajectory curvatures that occurred in the outer jet regions at different core separations. The bulk Lorentz factor, Doppler factor, and viewing angle of their motion are derived. The unusual jet-direction change of ∼100° observed in 2010–2011 can be naturally explained. Conclusions. We propose a double-jet structure scenario for 3C279 and suggest that there may be a supermassive black hole binary in the center of 3C279 ejecting two precessing relativistic jets, resulting in its very complex structure and kinematics on parsec scales, and with extremely variable emission across the electromagnetic spectrum. Because the two jets have the same precession period, the precession of the double jet may have originated from the modulation of their jet orientation by the change in their orbital velocity direction relative to the observer. In this case the mass ratio m/M of the binary is approximately equal to the ratio of the jet cone widths, being on the order of ∼0.5.

scholarly journals The X-ray plateau phase of gamma-ray burst originating from an expanding shell with a Lorentz factor of a few tens

2021 ◽  
Author(s):  
Hüsne Dereli-Bégué ◽  
Asaf Pe'er ◽  
Felix Ryde ◽  
Sam R. Oates ◽  
Bing Zhang ◽  
...  
Keyword(s):  
Scaling Laws ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Plateau Phase ◽  
Relativistic Jets ◽  
Expansion Phase ◽  
X Ray ◽  
Self Similar ◽  
The Universe

Abstract Gamma-ray bursts (GRBs) are one of the most energetic explosions known in the Universe and are also known to have the most relativistic jets, with initial expansion Lorentz factors of $100< \Gamma_i <1000$ \cite{KP91, Fenimore+93, WL95, LS01, ZLB11, Zou+11, Racusin+11}. Many of these objects have a plateau in their early X-ray light curves (up to thousands of seconds) \cite{Nousek+06, OBrien+06, Zhang+06, Liang+07, Srinivasaragavan+20}. In this phase, the X-ray flux decreases much slower than theoretically expected \cite{MR93} which has puzzled the community for many years. Here, we show that the observed signal during this phase in both the X-ray and the optical bands is naturally obtained within the classical GRB “fireball” model, provided that (i) the initial Lorentz factor of the relativistically expanding jet is of the order of a few tens, rather than a few hundreds, as is often cited in the literature, and (ii) the expansion occurs into a medium-low density “wind” with density typically 3-4 orders of magnitude below the expectation from a Wolf-Rayet star \cite{CL99}. Within this framework, the end of the “plateau” phase (the beginning of the regular afterglow) marks the transition from the coasting phase to the self-similar expansion phase, which follows the scaling laws first derived by Blandford \& McKee.\cite{BM76}. This result therefore implies that the long GRB progenitors are either (i) not Wolf-Rayet stars, or (ii) the properties of the wind ejected by these stars prior to their final explosion are very different than the properties of the wind ejected at earlier times. This result shows that the range of Lorentz factors in GRB jets is much wider than previously thought, and bridges an observational ‘gap’ between mildly relativistic jets\cite{Ghisellini1993} inferred in active galactic nuclei, $\Gamma_i\lesssim 20$, to the much higher Lorentz factors, $\Gamma_i\lesssim 1000$ inferred in a few extreme GRBs\cite{Racusin+11}.

scholarly journals Revealing Short GRB Jet Structure and Dynamics with Gravitational Wave Electromagnetic Counterparts

2017 ◽  
Vol 13 (S338) ◽  
pp. 1-8
Author(s):  
Gavin P. Lamb ◽  
Shiho Kobayashi
Keyword(s):  
Gravitational Wave ◽  
Gamma Ray ◽  
Compact Object ◽  
Gamma Ray Bursts ◽  
Viewing Angle ◽  
Hidden Population ◽  
Structure And Dynamics ◽  
Optical Transients ◽  
Jet Structure

AbstractCompact object mergers are promising candidates for the progenitor system of short gamma-ray bursts (GRBs). Using gravitational wave (GW) triggers to identify a merger, any electromagnetic (EM) counterparts from the jet can be used to constrain the dynamics and structure of short GRB jets. GW triggered searches could reveal a hidden population of optical transients associated with the short-lived jets from the merger object. If the population of merger-jets is dominated by low-Lorentz-factors, then a GW triggered search will reveal the on-axis orphan afterglows from these failed GRBs. By considering the EM counterparts from a jet, with or without the prompt GRB, the jet structure and dynamics can be constrained. By modelling the afterglow of various jet structures with viewing angle, we provide observable predictions for the on- and off- axis EM jet counterparts. The predictions provide an indication for the various features expected from the proposed jet structure models.

scholarly journals Optical Afterglows as Probes for the Central Engine and Fireball of Gamma-Ray Bursts

2012 ◽  
Vol 8 (S290) ◽  
pp. 263-264
Author(s):  
Liang Li ◽  
En-Wei Liang ◽  
He Gao ◽  
Bing Zhang
Keyword(s):  
Statistical Analysis ◽  
Gamma Rays ◽  
Density Profile ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Gamma Ray Bursts ◽  
Prompt Gamma ◽  
Medium Density ◽  
Central Engine ◽  
Prompt Emission

AbstractWell-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are compiled from literature. We identify possible emission components based on our empirical fits and present statistical analysis for these components. We find that the flares are related to prompt emission, suggesting that they could have the same origin in different episodes. The shallow decay segment is not correlated with prompt gamma-rays. It likely signals a long-lasting injected wind from GRB central engines. Early after onset peak is closely related with prompt emission. The ambient medium density profile is likely n ∝ r−1. No correlation between the late re-brightening bump and prompt gamma-rays or the onset bump is found. They may be from another jet component.

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