Homologously collapsing stellar cores

Goldreich, Peter; Weber, S. V.

doi:10.1086/158065

Cited by 239 publications

(248 citation statements)

References 5 publications

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“…At ρ c ≈ 10 3 g cm −3 the deviation from homology is evident. Goldreich & Weber (1980) found analytically that in Newtonian theory a star with polytropic index Γ = 4/3 should contract strictly homologously. The deviation from homologous collapse observed in the simulation is mainly due to effects of general relativity: time dilation results in a slower advance of local proper time τ (r) near the center of the star, and the proper volume element √ −gdr is larger than in Newtonian gravity.…”

Section: Evolution Of Collapsing Smsmentioning

confidence: 98%

Spherical collapse of supermassive stars: Neutrino emission and gamma-ray bursts

Linke

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Janka

et al. 2001

A&A

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Abstract. We present the results of numerical simulations of the spherically symmetric gravitational collapse of supermassive stars (SMS). The collapse is studied using a general relativistic hydrodynamics code. The coupled system of Einstein and fluid equations is solved employing coordinates adapted to a foliation of the spacetime by means of outgoing null hypersurfaces. The code contains an equation of state which includes effects due to radiation, electrons and baryons, and detailed microphysics to account for electron-positron pairs. In addition energy losses by thermal neutrino emission are included. We are able to follow the collapse of SMS from the onset of instability up to the point of black hole formation. Several SMS with masses in the range 5 × 10 5 M −10 9 M are simulated. In all models an apparent horizon forms initially, enclosing the innermost 25% of the stellar mass. From the computed neutrino luminosities, estimates of the energy deposition by νν-annihilation are obtained. Only a small fraction of this energy is deposited near the surface of the star, where, as proposed recently by , it could cause the ultrarelativistic flow believed to be responsible for γ-ray bursts. Our simulations show that for collapsing SMS with masses larger than 5 × 10 5 M the energy deposition is at least two orders of magnitude too small to explain the energetics of observed long-duration bursts at cosmological redshifts. In addition, in the absence of rotational effects the energy is deposited in a region containing most of the stellar mass. Therefore relativistic ejection of matter is impossible.

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Section: Evolution Of Collapsing Smsmentioning

confidence: 98%

Spherical collapse of supermassive stars: Neutrino emission and gamma-ray bursts

Linke

Font

Janka

et al. 2001

A&A

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“…As the initial iron core collapses, an inner, homologous core will maintain a roughly self-similar, index 3 polytropic structure [26,39]. This makes intuitive sense because the pressure support in the star is dominated by relativistically degenerate electrons with Fermi level (chemical potential) µ e ≈ 11.1 MeV(ρ 10 Y e ) 1/3 , where ρ 10 is the density in units of 10 10 g cm −3 .…”

Section: Effect Of Shock Wave Passagementioning

confidence: 99%

Sterile neutrino-enhanced supernova explosions

Hidaka

Fuller

2007

Phys. Rev. D

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We investigate the enhancement of lepton number, energy, and entropy transport resulting from active-sterile neutrino conversion νe → νs deep in the post-bounce supernova core followed by reconversion νs → νe further out, near the neutrino sphere. We explicitly take account of shock wave and neutrino heating modification of the active neutrino forward scattering potential which governs sterile neutrino production. We find that the νe luminosity at the neutrino sphere could be increased by between ∼ 10 % and ∼ 100 % during the crucial shock re-heating epoch if the sterile neutrino has a rest mass and vacuum mixing parameters in ranges which include those required for viable sterile neutrino dark matter. We also find sterile neutrino transport-enhanced entropy deposition ahead of the shock. This "pre-heating" can help melt heavy nuclei and thereby reduce the nuclear photo-dissociation burden on the shock. Both neutrino luminosity enhancement and pre-heating could increase the likelihood of a successful core collapse supernova explosion.

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“…When silicon shell burning pushes the iron core over its effective Chandrasekhar mass, collapse is initiated by a combination of electron capture and photo-disintegration of heavy nuclei, both leading to a depletion of central pressure support. Massive stars in the approximate mass range of about 10 to 100 solar masses (M ⊙ ) experience such a collapse phase until their homologously contracting [1,2] inner core reaches densities near and above nuclear saturation density where the nuclear equation of state (EoS) stiffens, leading to an almost instantaneous rebound of the inner core (core bounce) into the still supersonically infalling outer core. The hydrodynamic supernova shock is born, travels outward in radius and mass, but rapidly loses its kinetic energy to the dissociation of infalling iron-group nuclei and to neutrinos that deleptonize the immediate postshock material and stream off from these regions quasi-freely.…”

Section: Introductionmentioning

confidence: 99%

Gravitational wave burst signal from core collapse of rotating stars

et al. 2008

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We present results from detailed general relativistic simulations of stellar core collapse to a protoneutron star, using two different microphysical nonzero-temperature nuclear equations of state as well as an approximate description of deleptonization during the collapse phase. Investigating a wide variety of rotation rates and profiles as well as masses of the progenitor stars and both equations of state, we confirm in this very general setup the recent finding that a generic gravitational wave burst signal is associated with core bounce, already known as type I in the literature. The previously suggested type II (or "multiple-bounce") waveform morphology does not occur. Despite this reduction to a single waveform type, we demonstrate that it is still possible to constrain the progenitor and postbounce rotation based on a combination of the maximum signal amplitude and the peak frequency of the emitted gravitational wave burst. Our models include to sufficient accuracy the currently known necessary physics for the collapse and bounce phase of core-collapse supernovae, yielding accurate and reliable gravitational wave signal templates for gravitational wave data analysis. In addition, we assess the possiblity of nonaxisymmetric instabilities in rotating nascent proto-neutron stars. We find strong evidence that in an iron core-collapse event the postbounce core cannot reach sufficiently rapid rotation to become subject to a classical bar-mode instability. However, many of our postbounce core models exhibit sufficiently rapid and differential rotation to become subject to the recently discovered dynamical instability at low rotation rates.

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Homologously collapsing stellar cores

Abstract: We investigate the collapse of nonrotating gas sp~eres with a polytropic.equ~tion of state.: n = 3, corresponding toy = 4/3. Such polytropes provide~ re~sonable approximatiOn t Show more

Cited by 239 publications

References 5 publications

Spherical collapse of supermassive stars: Neutrino emission and gamma-ray bursts

Spherical collapse of supermassive stars: Neutrino emission and gamma-ray bursts

Sterile neutrino-enhanced supernova explosions

Gravitational wave burst signal from core collapse of rotating stars

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