scholarly journals Fallback Accretion Halted by R-process Heating in Neutron Star Mergers and Gamma-Ray Bursts

2021 ◽  
Vol 922 (2) ◽  
pp. 185
Author(s):  
Wataru Ishizaki ◽  
Kenta Kiuchi ◽  
Kunihito Ioka ◽  
Shinya Wanajo
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Pressure Gradients ◽  
Escape Velocity ◽  
Power Law Model ◽  
Hydrodynamic Simulations ◽  
One Dimensional ◽  
Wave Event ◽  
Process Heating ◽  
R Process

Abstract The gravitational wave event GW170817 with a macronova/kilonova shows that a merger of two neutron stars ejects matter with radioactivity including r-process nucleosynthesis. A part of the ejecta inevitably falls back to the central object, possibly powering long-lasting activities of a short gamma-ray burst (sGRB), such as extended and plateau emissions. We investigate fallback accretion with r-process heating by performing one-dimensional hydrodynamic simulations and developing a semi-analytical model. We show that the usual fallback rate dM/dt ∝ t −5/3 is halted by the heating because pressure gradients accelerate ejecta beyond an escape velocity. The suppression is steeper than Chevalier’s power-law model through Bondi accretion within a turn-around radius. The characteristic halting timescale is ∼104–108 s for the GW170817-like r-process heating, which is longer than the typical timescale of the long-lasting emission of sGRBs. The halting timescale is sensitive to the uncertainty of the r-process. Future observations of fallback halting could constrain the r-process heating on the scale of a year.

A One-Dimensional Relativistic Shock Model for the Light Curve of Gamma-ray Bursts

2006 ◽  
Vol 6 (3) ◽  
pp. 323-330 ◽  
Author(s):  
Cheng-Yue Su ◽  
Yi-Ping Qin ◽  
Jun-Hui Fan ◽  
Zhang-Yu Han
Keyword(s):  
Light Curve ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Shock Model ◽  
One Dimensional ◽  
Relativistic Shock

scholarly journals Neutrino fluence from gamma-ray bursts: off-axis view of structured jets

2019 ◽  
Vol 490 (4) ◽  
pp. 4935-4943 ◽  
Author(s):  
Markus Ahlers ◽  
Lea Halser
Keyword(s):  
Gravitational Wave ◽  
Angular Dependence ◽  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Scaling Relation ◽  
Model Predictions ◽  
Wave Event ◽  
Axis View

ABSTRACT We investigate the expected high-energy neutrino fluence from internal shocks produced in the relativistic outflow of gamma-ray bursts. Previous model predictions have primarily focused on on-axis observations of uniform jets. Here, we present a generalization to account for arbitrary viewing angles and jet structures. Based on this formalism, we provide an improved scaling relation that expresses off-axis neutrino fluences in terms of on-axis model predictions. We also find that the neutrino fluence from structured jets can exhibit a strong angular dependence relative to that of gamma-rays and can be far more extended. We examine this behaviour in detail for the recent short gamma-ray burst GRB 170817A observed in coincidence with the gravitational wave event GW170817.

R-process in Supernovae and Gamma-Ray Bursts

2010 ◽  
Author(s):  
T. Kajino ◽  
S. Harikae ◽  
T. Yoshida ◽  
K. Nakamura ◽  
W. Aoki ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
R Process

scholarly journals The Gamma-Ray Spectrum of Classical Novae

1996 ◽  
Vol 158 ◽  
pp. 303-304
Author(s):  
M. Hernanz ◽  
J. José ◽  
J. Gómez
Keyword(s):  
Gamma Ray ◽  
Hydrodynamic Simulations ◽  
One Dimensional ◽  
Classical Novae ◽  
Classical Nova ◽  
Expansion Stage ◽  
Hydrodynamic Code ◽  
Nova Outbursts ◽  
Significant Mass Loss ◽  
Significant Mass

AbstractWe report on preliminary hydrodynamic simulations of thermonuclear runaways in the hydrogen-rich envelopes of accreting white dwarfs, leading to nova outbursts. A one-dimensional, Lagrangian, implicit, hydrodynamic code (Kutter & Sparks 1972) has been used to reproduce the gross features of a classical nova, from the onset of accretion, through the progress of the outburst up to the expansion stage, where significant mass loss takes place. Special interest is focused on the synthesis of 22Na and 26Al, for their interest in γ-ray line astrophysics. The γ-ray spectrum is built by means of a Monte Carlo simulation.

scholarly journals The First Steps in the Life of a GRB

2005 ◽  
Vol 192 ◽  
pp. 483-489
Author(s):  
Miguel A. Aloy
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Relativistic Hydrodynamic ◽  
Gamma Ray Burst ◽  
Hydrodynamic Simulations ◽  
Preliminary Results

SummaryWe present some preliminary results of relativistic hydrodynamic simulations of post-neutron star merger disks as potential candidates for progenitors of short-lasting gamma-ray bursts. We discuss some of the generic conditions under which a gamma-ray burst can be initiated in this kind of progenitor and the main characteristics of the resulting outflow.

scholarly journals Imprints of r-process heating on fall-back accretion: distinguishing black hole–neutron star from double neutron star mergers

2019 ◽  
Vol 485 (3) ◽  
pp. 4404-4412 ◽  
Author(s):  
D Desai ◽  
B D Metzger ◽  
F Foucart
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Gamma Ray ◽  
Late Time ◽  
X Ray ◽  
Power Law Decay ◽  
Process Heating ◽  
R Process ◽  
The Impact

ABSTRACT Mergers of compact binaries containing two neutron stars (NS–NS), or a neutron star and a stellar mass black hole (NS–BH), are likely progenitors of short-duration gamma-ray bursts (SGRBs). A fraction ${\gtrsim } 20{{\ \rm per\ cent}}$ of SGRBs is followed by temporally extended (≳minute-long), variable X-ray emission, attributed to ongoing activity of the central engine. One source of late-time engine activity is fall-back accretion of bound tidal ejecta; however, observed extended emission light curves do not track the naively anticipated, uninterrupted t−5/3 power-law decay, instead showing a lull or gap in emission typically lasting tens of seconds after the burst. Here, we re-examine the impact of heating due to rapid neutron capture (r-process) nucleosynthesis on the rate of the fall-back accretion, using ejecta properties extracted from numerical relativity simulations of NS–BH mergers. Heating by the r-process has its greatest impact on marginally bound matter, hence its relevance to late-time fall-back. Depending on the electron fraction of the ejecta and the mass of the remnant black hole, r-process heating can imprint a range of fall-back behaviour, ranging from temporal gaps of up to tens of seconds to complete late-time cut-off in the accretion rate. This behaviour is robust to realistic variations in the nuclear heating experienced by different parts of the ejecta. Central black holes with masses ${\lesssim } 3\, \mathrm{M}_{\odot }$ typically experience absolute cut-offs in the fall-back rate, while more massive ${\gtrsim } 6\!-\!8\, \mathrm{M}_{\odot }$ black holes instead show temporal gaps. We thus propose that SGRBs showing extended X-ray emission arise from NS–BH, rather than NS–NS, mergers. Our model implies an NS–BH merger detection rate by LIGO that, in steady state, is comparable to or greater than that of NS–NS mergers.

scholarly journals Electromagnetic Precursors of Short Gamma-Ray Bursts as Counterparts of Gravitational Waves

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 104
Author(s):  
Jie-Shuang Wang ◽  
Liang-Duan Liu
Keyword(s):  
Black Hole ◽  
Gravitational Wave ◽  
Gamma Ray ◽  
Interaction Model ◽  
Gamma Ray Bursts ◽  
Opening Angle ◽  
Local Universe ◽  
Wave Event ◽  
Low Mass ◽  
Electromagnetic Precursors

Precursor emissions are found in some short gamma-ray bursts (SGRBs). In this paper, we review the theories and observations of the SGRB precursor and discuss its prospect as an electromagnetic counterpart of the gravitational wave event produced by neutron star (NS) mergers. The observed luminosity, spectrum, and duration of precursors are explained by the magnetospheric interaction model during the inspiral or the cocoon/jet shock breakout model during the jet propagation. In general, these two models predict that the precursor will be weaker than the main GRB, but will be of a larger opening angle, which makes it an advantageous gamma-ray counterpart for NS mergers in the local Universe, especially for NS - black hole mergers with very low mass ratios, in which the main GRBs are not expected. The joint observation of the precursor, SGRB, and gravitational wave will help to reveal the jet launch mechanism and post-merger remnant.

scholarly journals Neutron star mergers as sites of r-process nucleosynthesis and short gamma-ray bursts

2018 ◽  
Vol 27 (13) ◽  
pp. 1842005 ◽  
Author(s):  
Kenta Hotokezaka ◽  
Paz Beniamini ◽  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Near Infrared ◽  
Gamma Ray ◽  
Ultra Violet ◽  
Gamma Ray Bursts ◽  
Galactic Model ◽  
Multi Wavelength ◽  
R Process ◽  
Process Elements

Neutron star mergers have been long considered as promising sites of heavy [Formula: see text]-process nucleosynthesis. We overview the observational evidence supporting this scenario including: the total amount of [Formula: see text]-process elements in the galaxy, extreme metal-poor stars, geological radioactive elemental abundances, dwarf galaxies and short gamma-ray bursts (sGRBs). Recently, the advanced LIGO and Virgo observatories discovered a gravitational-wave signal of a neutron star merger, GW170817, as well as accompanying multi-wavelength electromagnetic (EM) counterparts. The ultra-violet, optical and near infrared (n/R) observations point to [Formula: see text]-process elements that have been synthesized in the merger ejecta. The rate and ejected mass inferred from GW170817 and the EM counterparts are consistent with other observations. We however, find that, within the simple one zone chemical evolution models (based on merger rates with reasonable delay time distributions as expected from evolutionary models, or from observations of sGRBs), it is difficult to reconcile the current observations of the Eu abundance history of galactic stars for [Fe/H] [Formula: see text]. This implies that to account for the role of mergers in the galactic chemical evolution, we need a galactic model with multiple populations that have different spatial distributions and/or varying formation rates.

scholarly journals Are Gamma-Ray Bursts Signals of Supermassive Black Hole Formation?

1999 ◽  
Vol 194 ◽  
pp. 235-240
Author(s):  
K. Abazajian ◽  
G. Fuller ◽  
X. Shi
Keyword(s):  
Flux Distribution ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Hole Formation ◽  
Spectral Parameters ◽  
Major Drawback ◽  
One Dimensional ◽  
Peak Flux ◽  
Loading Problem ◽  
Γ Ray

The formation of supermassive black holes through the gravitational collapse of supermassive objects (M ≳ 5 × 104 M⊙) has been proposed as a source of cosmological γ-ray bursts. The major advantage of this model is that such collapses are far more energetic than stellar-remnant mergers. The major drawback of this idea is the severe baryon loading problem in one-dimensional models. We can show that the observed log N - log P (number vs. peak flux) distribution for gamma-ray bursts in the BATSE database is not inconsistent with an identification of supermassive object collapse as the origin of the gamma-ray bursts. This conclusion is valid for a range of plausible cosmological and γ-ray burst spectral parameters.

scholarly journals One Dimensional Hydrodynamics of Asteroid-Neutron Star Collisions

1980 ◽  
Vol 58 ◽  
pp. 591-594
Author(s):  
Michael J. Newman ◽  
Arthur N. Cox
Keyword(s):  
Neutron Star ◽  
Solid Body ◽  
Gamma Ray ◽  
Compact Object ◽  
Gamma Ray Bursts ◽  
Radiation Diffusion ◽  
Gamma Ray Burst ◽  
One Dimensional

It has been suggested by several authors (e.g., Harwit and Salpeter, 1973) that the observed cosmic gamma-ray bursts might be produced by the collision of comet or asteroid-sized bodies with a compact object. Colgate and Petschek (1980) have discussed the tidal breakup of a solid body approaching a neutron star in central impact, with particular application to the cosmic gamma-ray burst of March 5, 1979. In this work we present the results of simplified one-dimensional hydrodynamic-radiation diffusion calculations of such an occurence.

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