Dynamic spherical collapses towards growing black holes in relativistically degenerate or hot host mass reservoirs

2019 ◽  
Author(s):  
Yu-Qing Lou ◽  
Wei Shen
Keyword(s):  
Black Holes ◽  
Compact Objects ◽  
Effective Pressure ◽  
Solution Type ◽  
Hot Matter ◽  
Important Solution ◽  
Supernova Explosions ◽  
General Relativistic ◽  
Self Similar ◽  
Similar Dynamic

Abstract We study the self-similar spherical hydrodynamics of γ = 4/3, with or without shocks, of general polytropic (GP) relativistically degenerate or hot matter in global mass reservoirs under the Paczynski-Wiita (PW) gravity that retains essential general relativistic (GR) effects for dynamic accretions onto growing Schwarzschild black holes (BHs). Various self-similar dynamic solutions can be derived and constructed. Among others, one important solution type is the expansion-wave collapse solution (EWCS) with a central BH event horizon in expansion. Such GP dynamic collapses are highly efficient for the rapid dynamic growth of supermassive and hypermassive BHs (SMBHs and HMBHs) in the Universe including the early Universe, in contrast to much slower disk mass accretion and BH merger processes. Particularly, the extra degree of freedom for the effective pressure of those relativistically degenerate or hot mass reservoirs makes it possible to construct for EWCSs with even higher efficiency for BH growths. Pertinent astrophysical applications of our model also include dynamic core collapses of massive or very massive stars or supermassive stars and compact objects as well as supernova explosions. Under joint actions of effective pressure and the PW gravity, self-similar dynamic solutions with central expanding spherical voids or cavities with either sharp or smooth density transitions across their rims can emerge. Dynamic expansion shocks are also constructed and examined.

scholarly journals Modeling the outcome of supernova explosions in binary population synthesis using the stellar compactness

2021 ◽  
Author(s):  
Maciej Dabrowny ◽  
Nicola Giacobbo ◽  
Davide Gerosa
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Binary Stars ◽  
Compact Objects ◽  
Population Synthesis ◽  
Subsequent Formation ◽  
Compact Binaries ◽  
Mass Gap ◽  
Supernova Explosions

AbstractFollowing the collapse of their cores, some of the massive binary stars that populate our Universe are expected to form merging binaries composed of black holes and neutron stars. Gravitational-wave observations of the resulting compact binaries can reveal precious details on the inner workings of the supernova mechanism and the subsequent formation of compact objects. Within the framework of the population-synthesis code mobse, we present the implementation of a new supernova model that relies on the compactness of the collapsing star. The model has two free parameters, namely the compactness threshold that separates the formation of black holes and that of neutron stars, and the fraction of the envelope that falls back onto the newly formed black holes. We compare this model extensively against other prescriptions that are commonly used in binary population synthesis. We find that the cleanest signatures of the role of the pre-supernova stellar compactness are (1) the relative formation rates of the different kinds of compact binaries, which mainly depend on the compactness threshold parameter, and (2) the location of the upper edge of the mass gap between the lightest black holes and the heaviest neutron stars, which mainly depends on the fallback fraction.

scholarly journals Numerical modeling of core-collapse supernovae and compact objects

2012 ◽  
Vol 8 (S291) ◽  
pp. 67-72
Author(s):  
Kohsuke Sumiyoshi
Keyword(s):  
Black Holes ◽  
Numerical Modeling ◽  
Nuclear Physics ◽  
Large Scale ◽  
Massive Stars ◽  
Compact Objects ◽  
Numerical Studies ◽  
Supernova Explosions ◽  
Full Knowledge ◽  
Unsolved Issue

AbstractMassive stars (M ≥ 10M⊙) end their lives with spectacular explosions due to gravitational collapse. The collapse turns the stars into compact objects such as neutron stars and black holes with the ejection of cosmic rays and heavy elements. Despite the importance of these astrophysical events, the mechanism of supernova explosions has been an unsolved issue in astrophysics. This is because clarification of the supernova dynamics requires the full knowledge of nuclear and neutrino physics at extreme conditions, and large-scale numerical simulations of neutrino radiation hydrodynamics in multi-dimensions. This article is a brief overview of the understanding (with difficulty) of the supernova mechanism through the recent advance of numerical modeling at supercomputing facilities. Numerical studies with the progress of nuclear physics are applied to follow the evolution of compact objects with neutrino emissions in order to reveal the birth of pulsars/black holes from the massive stars.

scholarly journals Bootstrapped Newtonian stars and black holes

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Roberto Casadio ◽  
Michele Lenzi ◽  
Octavian Micu
Keyword(s):  
Black Holes ◽  
Gravitational Potential ◽  
Strong Field ◽  
Compact Objects ◽  
Newtonian Gravity ◽  
Speed Of Light ◽  
Relativistic Case ◽  
Test Particles ◽  
Equilibrium Configurations ◽  
General Relativistic

Abstract We study equilibrium configurations of a homogenous ball of matter in a bootstrapped description of gravity which includes a gravitational self-interaction term beyond the Newtonian coupling. Both matter density and pressure are accounted for as sources of the gravitational potential for test particles. Unlike the general relativistic case, no Buchdahl limit is found and the pressure can in principle support a star of arbitrarily large compactness. By defining the horizon as the location where the escape velocity of test particles equals the speed of light, like in Newtonian gravity, we find a minimum value of the compactness for which this occurs. The solutions for the gravitational potential here found could effectively describe the interior of macroscopic black holes in the quantum theory, as well as predict consequent deviations from general relativity in the strong field regime of very compact objects.

scholarly journals Microquasars and ULXS: Fossils of GRB Sources

2004 ◽  
Vol 194 ◽  
pp. 14-17 ◽  
Author(s):  
I. F. Mirabell
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Binary Systems ◽  
Gamma Ray ◽  
Massive Stars ◽  
Compact Objects ◽  
Primary Star ◽  
Long Duration ◽  
Supernova Explosions ◽  
Low Mass

AbstractGamma-ray bursts (GRBs) of long duration probably result from the core-collapse of massive stars in binary systems. After the collapse of the primary star the binary system may remain bound leaving a microquasar or ULX source as remnant. In this context, microquasars and ULXs are fossils of GRB sources and should contain physical and astrophysical clues on their GRB-source progenitors. Here I show that the identification of the birth place of microquasars can provide constrains on the progenitor stars of compact objects, and that the runaway velocity can be used to constrain the energy in the explosion of massive stars that leave neutron stars and black holes. The observations show that the neutron star binaries LS 5039, LSI +61°303 and the low-mass black hole GRO J1655-40 formed in energetic supernova explosions, whereas the black holes of larger masses (M ≥ 10 M⊙) in Cygnus X-l and GRS 1915+105 formed promptly, in the dark or in underluminous supornovao. The association with clusters of massive stars of the microquasar LSI +61°303 and the magnetars SGR 1806-20 and SGR 1900+14, suggest that very massive stars (M ≥ 50 M⊙) may -in some cases- leave neutron stars rather than black holes. The models of GRB sources of long duration have the same basic ingredients as microquasars and ULXs: compact objects with accretion disks and relativistic jets in binary systems. Therefore, the analogies between microquasars and AGN may be extended to the sources of GRBs.

scholarly journals Static Spherically Symmetric Black Holes in Weak f(T)-Gravity

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 153
Author(s):  
Christian Pfeifer ◽  
Sebastian Schuster
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Teleparallel Gravity ◽  
Compact Objects ◽  
Spherically Symmetric ◽  
Static Vacuum ◽  
Perihelion Shift ◽  
General Relativistic ◽  
Vacuum Spacetime ◽  
Near Future

With the advent of gravitational wave astronomy and first pictures of the “shadow” of the central black hole of our milky way, theoretical analyses of black holes (and compact objects mimicking them sufficiently closely) have become more important than ever. The near future promises more and more detailed information about the observable black holes and black hole candidates. This information could lead to important advances on constraints on or evidence for modifications of general relativity. More precisely, we are studying the influence of weak teleparallel perturbations on general relativistic vacuum spacetime geometries in spherical symmetry. We find the most general family of spherically symmetric, static vacuum solutions of the theory, which are candidates for describing teleparallel black holes which emerge as perturbations to the Schwarzschild black hole. We compare our findings to results on black hole or static, spherically symmetric solutions in teleparallel gravity discussed in the literature, by comparing the predictions for classical observables such as the photon sphere, the perihelion shift, the light deflection, and the Shapiro delay. On the basis of these observables, we demonstrate that among the solutions we found, there exist spacetime geometries that lead to much weaker bounds on teleparallel gravity than those found earlier. Finally, we move on to a discussion of how the teleparallel perturbations influence the Hawking evaporation in these spacetimes.

Beyond the Schwarzschild Metric

2018 ◽  
Author(s):  
David M. Wittman
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Gravitational Waves ◽  
Test Particle ◽  
Direct Detection ◽  
Relativistic Effects ◽  
Big Bang ◽  
Clusters Of Galaxies ◽  
General Relativistic ◽  
The Universe

General relativity explains much more than the spacetime around static spherical masses.We briefly assess general relativity in the larger context of physical theories, then explore various general relativistic effects that have no Newtonian analog. First, source massmotion gives rise to gravitomagnetic effects on test particles.These effects also depend on the velocity of the test particle, which has substantial implications for orbits around black holes to be further explored in Chapter 20. Second, any changes in the sourcemass ripple outward as gravitational waves, and we tell the century‐long story from the prediction of gravitational waves to their first direct detection in 2015. Third, the deflection of light by galaxies and clusters of galaxies allows us to map the amount and distribution of mass in the universe in astonishing detail. Finally, general relativity enables modeling the universe as a whole, and we explore the resulting Big Bang cosmology.

GR-AMRVAC code applications: accretion onto compact objects, boson stars versus black holes

2016 ◽  
Vol 33 (15) ◽  
pp. 155010 ◽  
Author(s):  
Z Meliani ◽  
P Grandclément ◽  
F Casse ◽  
F H Vincent ◽  
O Straub ◽  
...  
Keyword(s):  
Black Holes ◽  
Compact Objects ◽  
Boson Stars
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