Numerical Simulations of Relativistic Jets in Collapsars PDF Download

Author: Weiqun Zhang
Publisher:
ISBN:
Category : Astrophysical jets
Languages : en
Pages : 266

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
Two-dimensional MHD simulations are performed using the ZEUS-2D code to investigate the dynamics of a collapsar that generates a GRB jet, taking account of realistic equation of state, neutrino cooling and heating processes, magnetic fields, and gravitational force from the central black hole and self-gravity. It is found that neutrino heating processes are not efficient enough to launch a jet in this study. It is also found that a jet is launched mainly by B{sub {phi}} fields that are amplified by the winding-up effect. However, since the ratio of total energy relative to the rest-mass energy in the jet is not as high as several hundred, we conclude that the jets seen in this study are not GRB jets. This result suggests that general relativistic effects will be important to generating a GRB jet. Also, the accretion disk with magnetic fields may still play an important role in launching a GRB jet, although a simulation for much longer physical time ((almost equal to)10-100 s) is required to confirm this effect. It is shown that a considerable amount of 56Ni is synthesized in the accretion disk. Thus, there will be a possibility for the accretion disk to supply the sufficient amount of 56Ni required to explain the luminosity of a hypernova. Also, it is shown that neutron-rich matter due to electron captures with high entropy per baryon is ejected along the polar axis. Thus, there will be a possibility that r-process nucleosynthesis occurs at such a region. Finally, many neutrons will be ejected from the jet, which suggests that signals from the neutron decays may be observed as the delayed bump of the light curve of the afterglow or gamma rays.

Author: Markus Boettcher
Publisher: John Wiley & Sons
ISBN: 3527641750
Category : Science
Languages : en
Pages : 425

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Written by a carefully selected consortium of researchers working in the field, this book fills the gap for an up-to-date summary of the observational and theoretical status. As such, this monograph includes all used wavelengths, from radio to gamma, the FERMI telescope, a history and theory refresher, and jets from gamma ray bursts. For astronomers, nuclear physicists, and plasmaphysicists.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 54

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Two-dimensional magnetohydrodynamic simulations are performed using the ZEUS-2D code to investigate the dynamics of a collapsar that generates a GRB jet, taking account of realistic equation of state, neutrino cooling and heating processes, magnetic fields, and gravitational force from the central black hole and self gravity. It is found that neutrino heating processes are not so efficient to launch a jet in this study. It is also found that a jet is launched mainly by B{sub {phi}} fields that are amplified by the winding-up effect. However, since the ratio of total energy relative to the rest mass energy in the jet is not so high as several hundred, we conclude that the jets seen in this study are not be a GRB jet. This result suggests that general relativistic effects, which are not included in this study, will be important to generate a GRB jet. Also, the accretion disk with magnetic fields may still play an important role to launch a GRB jet, although a simulation for much longer physical time ≈ 10-100 s is required to confirm this effect. It is shown that considerable amount of 56Ni is synthesized in the accretion disk. Thus there will be a possibility for the accretion disk to supply sufficient amount of 56Ni required to explain the luminosity of a hypernova. Also, it is shown that neutron-rich matter due to electron captures with high entropy per baryon is ejected along the polar axis. Moreover, it is found that the electron fraction becomes larger than 0.5 around the polar axis near the black hole by [nu]{sub e} capture at the region. Thus there will be a possibility that r-process and r/p-process nucleosynthesis occur at these regions. Finally, much neutrons will be ejected from the jet, which suggests that signals from the neutron decays may be observed as the delayed bump of the light curve of the afterglow or gamma-rays.

Author: Chris L. Fryer
Publisher: Springer Science & Business Media
ISBN: 9781402019920
Category : Mathematics
Languages : en
Pages : 454

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Supernovae, hypernovae and gamma-ray bursts are among the most energetic explosions in the universe. The light from these outbursts is, for a brief time, comparable to billions of stars and can outshine the host galaxy within which the explosions reside. Most of the heavy elements in the universe are formed within these energetic explosions. Surprisingly enough, the collapse of massive stars is the primary source of not just one, but all three of these explosions. As all of these explosions arise from stellar collapse, to understand one requires an understanding of the others. Stellar Collapse marks the first book to combine discussions of all three phenomena, focusing on the similarities and differences between them. Designed for graduate students and scientists newly entering this field, this book provides a review not only of these explosions, but the detailed physical models used to explain them from the numerical techniques used to model neutrino transport and gamma-ray transport to the detailed nuclear physics behind the evolution of the collapse to the observations that have led to these three classes of explosions.

Author: Miguel A. Aloy
Publisher:
ISBN:
Category :
Languages : en
Pages : 10

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Author: Silvano Massaglia
Publisher: Springer Science & Business Media
ISBN: 3540769668
Category : Science
Languages : en
Pages : 182

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The study of the mechanisms that govern origin and propagation of stellar jets involves the treatment of many concurrent physical processes such as gravitation, hydrodynamics and magnetohydrodynamics, atomic physics and radiation. In the past years, an intensive work has been done looking for so- tions of the ideal MHD equations in the steady state limit as well as studying the stability of out?ows in the linear regime. These kind, of approaches have provided a contribution to the understanding of jets that can hardly be ov- estimated. However, the extension of the analyses to the time-dependent and nonlinear regimes could not be avoided, and the MHD numerical simulations were the only mean to achieve this goal. Intherecentyears,considerableprogresseshavebeenmadebythecom- tational?uiddynamiccommunityinthedevelopmentofnumericaltechniques, theso-calledhighresolutionshockcapturingschemes,wellsuitedforthetre- ment of supersonic ?ows with discontinuities. The numerical simulations of astrophysical jets took advantage of these developments; however new physics needed to be incorporated, such as magnetic ?eld e?ects, radiation losses by diluted gases, and proper astrophysics environments. These needs led to the nontrivial extension of the methods devised for the Euler equations of g- dynamics to the magneto-hydrodynamical system. On the other hand, the possibility of carrying out numerical calculations has been greatly facilitated bytheavailability, ononehand,ofpowerfulsupercomputersand,ontheother hand, of fast processors at low cost. Large scale 3D simulations of jets at high resolution are now possible thanks to supercomputers, but also high reso- tion 2D MHD simulations can be performed routinely on desktop computers.

Author: E.E. Fenimore
Publisher: American Institute of Physics
ISBN:
Category : Science
Languages : en
Pages : 812

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In the last thirty years, gamma-ray bursts have grown from an oddity to a central position in astrophysics. Not only are they the largest explosions since the big bang, capable of flooding most of the universe with gamma-rays, but their brilliance serves as a backlight that can illuminate the cosmos far deeper into the early universe than any other object. Their unpredictability has forced researchers to use extreme measures to observe them: completely autonomous satellites and robotic ground-based telescopes. Their bizarre physical properties have pushed us to develop new theories of astrophysical explosions. Topics include: global properties of GRBs; X-ray flashes; ultra-high energy gamma-rays, neutrinos, gravity waves; prompt emission and early afterglows; relativistic jets and polarization; GRB030329; GRB progenitors; GRB connection to supernovae; dark versus bright GRBs; late afterglows; GRBs and cosmology; general observations; general theory; analysis and observation techniques; present satellites; Swift satellite; future satellites; and robotic observing systems.

Author: Eunwoo Choi
Publisher:
ISBN: 9781109982732
Category :
Languages : en
Pages : 139

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This dissertation describes a multidimensional relativistic hydrodynamic code which solves the special relativistic hydrodynamic equations as a hyperbolic system of conservation laws based on the total variation diminishing (TVD) scheme. Several standard tests and test simulations are presented to demonstrate the accuracy, robustness and flexibility of the code. Using this code we have studied three-dimensional hydrodynamic interactions of relativistic extragalactic jets with two-phase ambient media. The deflection angle of the jet is influenced more by the density contrast of the cloud than by the beam Mach number of the jet, and a relativistic jet with low relativistic beam Mach number can eventually be slightly bent after it crosses the dense cloud. Relativistic jet impacts on dense clouds do not necessarily destroy the clouds completely, and much of the cloud body can survive as a coherent blob due to the combination of the geometric influence of off-axis collisions and the lower rate of cloud fragmentation through the Kelvin-Helmholtz instability for relativistic flows. We find that relativistic jets interacting with clouds can produce synchrotron emission knots similar to structures observed in many VLBI-scale radio sources and the synchrotron emission peaks right before the jet passes through the cloud.

Author: Elena Vázquez-Cendón
Publisher: CRC Press
ISBN: 020356233X
Category : Mathematics
Languages : en
Pages : 434

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Numerical Methods for Hyperbolic Equations is a collection of 49 articles presented at the International Conference on Numerical Methods for Hyperbolic Equations: Theory and Applications (Santiago de Compostela, Spain, 4-8 July 2011). The conference was organized to honour Professor Eleuterio Toro in the month of his 65th birthday. The topics cover