Delayed neutrino-driven supernova explosions aided by the standing accretion-shock instability
TL;DR: In this article, the authors present two-dimensional hydrodynamic simulations of stellar core collapse and develop the framework for a detailed analysis of the energetic aspects of neutrino-powered supernova explosions.
Abstract: We present two-dimensional hydrodynamic simulations of stellar core collapse and develop the framework for a detailed analysis of the energetic aspects of neutrino-powered supernova explosions. Our results confirm that the neutrino-heating mechanism remains a viable explanation of the explosion of a wider mass range of supernova progenitors with iron cores, but the explosion sets in later and develops differently than thought so far. The calculations were performed with an energy-dependent treatment of the neutrino transport based on the ray-by-ray plus approximation, in which the neutrino number, energy, and momentum equations are closed with a variable Eddington factor obtained by iteratively solving a model Boltzmann equation. We focus here on the evolution of a 15 M ☉ progenitor and provide evidence that shock revival and an explosion are initiated at about 600 ms after core bounce, powered by neutrino energy deposition. This is significantly later than previously found for an 11.2 M ☉ star, for which we also present a continuation of the explosion model published by Buras et al. The onset of the blast is fostered in both cases by the standing accretion-shock instability. This instability exhibits highest growth rates for the dipole and quadrupole modes, which lead to large-amplitude bipolar shock oscillations and push the shock to larger radii, thus increasing the time accreted matter is exposed to neutrino heating in the gain layer. As a consequence, also convective overturn behind the shock is strengthened, which otherwise is suppressed or damped because of the small shock stagnation radius. When the explosion sets in, the shock reveals a pronounced global deformation with a dominant dipolar component. In both the 11.2 M ☉ and 15 M ☉ explosions long-lasting equatorial downflows supply the gain layer with fresh gas, of which a sizable fraction is heated by neutrinos and leads to the build-up of the explosion energy of the ejecta over possibly hundreds of milliseconds. A soft nuclear equation of state that causes a rapid contraction, and a smaller radius of the forming neutron star and thus a fast release of gravitational binding energy, seems to be more favorable for the development of an explosion. Rotation has the opposite effect because in the long run it leads to a more extended and cooler neutron star and thus lower neutrino luminosities and mean energies and overall less neutrino heating. Neutron star g-mode oscillations, although we see their presence, and the acoustic mechanism play no important role in our simulations. While numerical tests show that our code is also well able to follow large-amplitude core g-modes if they are instigated; the amplitude of such oscillations remains small in our supernova runs and the acoustic energy flux injected by the ringing neutron star and by the deceleration of supersonic downflows near the neutron star surface is small compared to the neutrino energy deposition.
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TL;DR: The neutrino-heating mechanism, aided by nonradial flows, drives explosions, albeit low-energy ones, of O-Ne-Mg-core and some Fe-core progenitors as mentioned in this paper.
Abstract: Supernova theory, numerical and analytic, has made remarkable progress in the past decade. This progress was made possible by more sophisticated simulation tools, especially for neutrino transport, improved microphysics, and deeper insights into the role of hydrodynamic instabilities. Violent, large-scale nonradial mass motions are generic in supernova cores. The neutrino-heating mechanism, aided by nonradial flows, drives explosions, albeit low-energy ones, of O-Ne-Mg-core and some Fe-core progenitors. The characteristics of the neutrino emission from newborn neutron stars were revised, new features of the gravitational-wave signals were discovered, our notion of supernova nucleosynthesis was shattered, and our understanding of pulsar kicks and explosion asymmetries was significantly improved. But simulations also suggest that neutrino-powered explosions might not explain the most energetic supernovae and hypernovae, which seem to demand magnetorotational driving. Now that modeling is being advanced from...
971 citations
TL;DR: In this paper, the authors derived the mass distributions of stellar compact remnants and provided analytic prescriptions for both single-star models (as a function of initial star mass) and binary-star model-prescriptions for compact object masses for major population synthesis codes.
Abstract: The mass distribution of neutron stars and stellar-mass black holes provides vital clues into the nature of stellar core collapse and the physical engine responsible for supernova explosions. A number of supernova engines have been proposed: neutrino- or oscillation-driven explosions enhanced by early (developing in 10-50 ms) and late-time (developing in 200 ms) convection as well as magnetic field engines (in black hole accretion disks or neutron stars). Using our current understanding of supernova engines, we derive mass distributions of stellar compact remnants. We provide analytic prescriptions for both single-star models (as a function of initial star mass) and for binary-star models-prescriptions for compact object masses for major population synthesis codes. These prescriptions have implications for a range of observations: X-ray binary populations, supernova explosion energies, and gravitational wave sources. We show that advanced gravitational radiation detectors (like LIGO/VIRGO or the Einstein Telescope) will be able to further test the supernova explosion engine models once double black hole inspirals are detected.
646 citations
TL;DR: In this article, the authors present results of a systematic study of failing core-collapse supernovae and the formation of stellar-mass black holes (BHs) using GR1D equipped with a three-species neutrino leakage/heating scheme.
Abstract: We present results of a systematic study of failing core-collapse supernovae and the formation of stellar-mass black holes (BHs). Using our open-source general-relativistic 1.5D code GR1D equipped with a three-species neutrino leakage/heating scheme and over 100 presupernova models, we study the effects of the choice of nuclear equation
of state (EOS), zero-age main sequence (ZAMS) mass and metallicity, rotation, and mass-loss prescription on
BH formation. We find that the outcome, for a given EOS, can be estimated, to first order, by a single parameter,
the compactness of the stellar core at bounce. By comparing protoneutron star (PNS) structure at the onset
of gravitational instability with solutions of the Tolman–Oppenheimer–Volkof equations, we find that thermal
pressure support in the outer PNS core is responsible for raising the maximum PNS mass by up to 25% above the
cold NS value. By artificially increasing neutrino heating, we find the critical neutrino heating efficiency required
for exploding a given progenitor structure and connect these findings with ZAMS conditions, establishing, albeit
approximately, for the first time based on actual collapse simulations, the mapping between ZAMS parameters and
the outcome of core collapse. We also study the effect of progenitor rotation and find that the dimensionless spin of
nascent BHs may be robustly limited below a* = Jc/GM^2 = 1 by the appearance of nonaxisymmetric rotational
instabilities.
575 citations
TL;DR: In this article, the authors derived mass distributions of stellar compact remnants and provided analytical prescriptions for compact object masses for major population synthesis codes, and demonstrated that these qualitatively new results for compact objects can explain the observed gap in the remnant mass distribution between ~2-5 solar masses and place strong constraints on the nature of the supernova engine.
Abstract: The mass distribution of neutron stars and stellar-mass black holes provides vital clues into the nature of stellar core collapse and the physical engine responsible for supernova explosions. Using recent advances in our understanding of supernova engines, we derive mass distributions of stellar compact remnants. We provide analytical prescriptions for compact object masses for major population synthesis codes. In an accompanying paper, Belczynski et al., we demonstrate that these qualitatively new results for compact objects can explain the observed gap in the remnant mass distribution between ~2-5 solar masses and that they place strong constraints on the nature of the supernova engine. Here, we show that advanced gravitational radiation detectors (like LIGO/VIRGO or the Einstein Telescope) will be able to further test the supernova explosion engine models once double black hole inspirals are detected.
499 citations
Cites background from "Delayed neutrino-driven supernova e..."
...One model allows for considerable contribution from the SASI engine, a current focus of many supernova groups (Blondin et al. 2003, Burrows et al. 2007, Bruenn et al. 2009, Scheck et al. 2008, Marek & Janka 2009)....
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TL;DR: In this paper, a spherically symmetric general relativistic radiation hydrodynamics using spectral three-flavor Boltzmann neutrino transport is used to simulate the collapse, bounce, explosion, and the neutrini-driven wind phases consistently over more than 20 s.
Abstract: Massive stars end their lives in explosions with kinetic energies on the order of 10 51 erg. Immediately after the explosion has been launched, a region of low density and high entropy forms behind the ejecta, which is continuously subject to neutrino heating. The neutrinos emitted from the remnant at the center, the protoneutron star (PNS), heat the material above the PNS surface. This heat is partly converted into kinetic energy, and the material accelerates to an outflow that is known as the neutrino-driven wind. For the first time we simulate the collapse, bounce, explosion, and the neutrino-driven wind phases consistently over more than 20 s. Our numerical model is based on spherically symmetric general relativistic radiation hydrodynamics using spectral three-flavor Boltzmann neutrino transport. In simulations where no explosions are obtained naturally, we model neutrino-driven explosions for low- and intermediatemass Fe-core progenitor stars by enhancing the charged current reaction rates. In the case of a special progenitor star, the 8. 8M � O-Ne-Mg-core, the explosion in spherical symmetry was obtained without enhanced opacities. The post-explosion evolution is in qualitative agreement with static steady-state and parametrized dynamic models of the neutrino-driven wind. On the other hand, we generally find lower neutrino luminosities and mean neutrino energies, as well as a different evolutionary behavior of the neutrino luminosities and mean neutrino energies. The neutrino-driven wind is proton-rich for more than 10 s and the contraction of the PNS differs from the assumptions made for the conditions at the inner boundary in previous neutrino-driven wind studies. Despite the moderately high entropies of about 100 kB/baryon and the fast expansion timescales, the conditions found in our models are unlikely to favor r-process nucleosynthesis. The simulations are carried out until the neutrino-driven wind settles down to a quasi-stationary state. About 5 s after the bounce, the peak temperature inside the PNS already starts to decrease because of the continued deleptonization. This moment determines the beginning of a cooling phase dominated by the emission of neutrinos. We discuss the physical conditions of the quasi-static PNS evolution and take the effects of deleptonization and mass accretion from early fallback into account.
481 citations
Cites background or result from "Delayed neutrino-driven supernova e..."
...These have been shown (see for example Miller et al. (1993), Herant et al. (1994), Burrows et al. (1995) and Janka and Müller (1996)) to increase the neutrino heating efficiency and help to understand aspherical explosions, see for example Bruenn et al. (2006) and Marek and Janka (2009)....
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...…neutrino spectra from these artificially induced explosions in spherical symmetry are in general agreement with the neutrino spectra from axially-symmetric neutrino driven core collapse supernova models that explode without artificially modified reaction rates (see Marek and Janka (2009))....
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References
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TL;DR: In this paper, the nucleosynthetic yield of isotopes lighter than A = 66 (zinc) is determined for a grid of stellar masses and metallicities including stars of 11, 12, 13, 15, 18, 19, 20, 22, 25, 30, 35, and 40 M{sub {circle_dot}} and metals Z = 0, 10{sup {minus}4}, 0.01, 0.1, and 1 times solar (a slightly reduced mass grid is employed for non-solar metallicities).
Abstract: The nucleosynthetic yield of isotopes lighter than A = 66 (zinc) is determined for a grid of stellar masses and metallicities including stars of 11, 12, 13, 15, 18, 19, 20, 22, 25, 30, 35, and 40 M{sub {circle_dot}} and metallicities Z = 0, 10{sup {minus}4}, 0.01, 0.1, and 1 times solar (a slightly reduced mass grid is employed for non-solar metallicities). Altogether 78 different model supernova explosions are calculated. In each case nucleosynthesis has already been determined for 200 isotopes in each of 600 to 1200 zones of the presupernova star, including the effects of time dependent convection. Here each star is exploded using a piston to give a specified final kinetic energy at infinity (typically 1.2 {times} 10{sup 51} erg), and the explosive modifications to the nucleosynthesis, including the effects of neutrino irradiation, determined. A single value of the critical {sup 12}C({sub {alpha},{gamma}}){sup 16}O reaction rate corresponding to S(300 keV) = 170 keV barns is used in all calculations. The synthesis of each isotope is discussed along with its sensitivity to model parameters. In each case, the final mass of the collapsed remnant is also determined and often found not to correspond to the location of the pistonmore » (typically the edge of the iron core), but to a ``mass cut`` farther out. This mass cut is sensitive not only to the explosion energy, but also to the presupernova structure, stellar mass, and the metallicity. Unless the explosion mechanism, for unknown reasons, provides a much larger characteristic energy in more massive stars, it appears likely that stars larger than about 30 M{sub {center_dot}} will experience considerable reimplosion of heavy elements following the initial launch of a successful shock. While such explosions will produce a viable, bright Type II supernova light curve, lacking the radioactive tail, they will have dramatically reduced yields of heavy elements and may leave black hole remnants of up to 10 and more solar masses.« less
3,649 citations
"Delayed neutrino-driven supernova e..." refers methods in this paper
...…M⊙ progenitor from Woosley et al. (2002), for which we show results from a continuation of the model run published by Buras et al. (2006b), all core-collapse and supernova calculations in this work are based on the 15 M⊙ progenitor s15s7b2 from Woosley & Weaver (1995) and are listed in Table 1....
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...In this work we considered a 15 M⊙ progenitor (s15s7b2 of Woosley & Weaver 1995) and an 11.2 M⊙ model (Woosley et al. 2002)....
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...We study here a 15 M⊙ model (s15s7b2 from Woosley & Weaver 1995) which is frequently used in previous and present core-collapse studies because it can be considered as representative of stars in a larger mass interval....
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TL;DR: In this article, the authors examined the current understanding of the lives and deaths of massive stars, with special attention to the relevant nuclear and stellar physics, and focused on their post-helium-burning evolution.
Abstract: amount of energy, a tiny fraction of which is sufficient to explode the star as a supernova. The authors examine our current understanding of the lives and deaths of massive stars, with special attention to the relevant nuclear and stellar physics. Emphasis is placed upon their post-helium-burning evolution. Current views regarding the supernova explosion mechanism are reviewed, and the hydrodynamics of supernova shock propagation and ‘‘fallback’’ is discussed. The calculated neutron star masses, supernova light curves, and spectra from these model stars are shown to be consistent with observations. During all phases, particular attention is paid to the nucleosynthesis of heavy elements. Such stars are capable of producing, with few exceptions, the isotopes between mass 16 and 88 as well as a large fraction of still heavier elements made by the r and p processes.
1,981 citations
"Delayed neutrino-driven supernova e..." refers background or methods in this paper
...Buras et al. (2006b) observed a similar situation in their 180-degree simulation of the collapse and post-bounce evolution of a (non-rotating) 11.2 M⊙ progenitor from Woosley et al. (2002)....
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...In this work we considered a 15 M⊙ progenitor (s15s7b2 of Woosley & Weaver 1995) and an 11.2 M⊙ model (Woosley et al. 2002)....
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...Investigated models Except for a simulation with an 11.2 M⊙ progenitor from Woosley et al. (2002), for which we show results from a continuation of the model run published by Buras et al. (2006b), all core-collapse and supernova calculations in this work are based on the 15 M⊙ progenitor s15s7b2…...
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TL;DR: In this paper, an equation of state for hot, dense matter is presented in a form that is sufficiently rapid to use directly in hydrodynamical simulations, for example, in stellar collapse calculations.
1,188 citations
"Delayed neutrino-driven supernova e..." refers background or methods or result in this paper
...They performed their simulations with the nuclear EoS of Shen et al. (1998), which is significantly stiffer than the Lattimer & Swesty (1991) EoS, though fairly similar to the Hillebrandt & Wolff EoS (Marek et al., in preparation; see also Janka et al. 2007)....
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...…one hand, and 2D models without rotation on the other, in which two different equations of state (EoSs) for supernova matter are used, namely the Lattimer & Swesty (1991) EoS with a soft nuclear phase and the Hillebrandt, Wolff, & Nomoto (1984; see also Hillebrandt & Wolff 1985) EoS with a…...
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...The positive trend towards a SASI-supported, neutrino-driven runaway late after bounce might be linked to a (relatively) soft equation of state for neutron star matter, like the EoS of Lattimer & Swesty (1991) used by us....
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...All these results were obtained with the EoS of Lattimer & Swesty (1991)....
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...Since we describe gravitational effects by the effective relativistic potential, our neutron stars are more compact (in particular with the softer EoS of Lattimer & Swesty 1991) than those in the Newtonian simulations of the Tucson group....
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TL;DR: In this article, the authors investigate how current and proposed observations of neutron stars can lead to an understanding of the state of their interiors and the key unknowns: the typical neutron star radius and the neutron star maximum mass.
1,024 citations
TL;DR: In this article, a theoretical analysis of neutron star structure, including general relativistic limits to mass, compactness, and spin rates, is presented. But the authors focus on the state of the interiors and the key unknowns: the typical neutron star radius and the maximum mass.
Abstract: We investigate how current and proposed observations of neutron stars can lead to an understanding of the state of their interiors and the key unknowns: the typical neutron star radius and the neutron star maximum mass. A theoretical analysis of neutron star structure, including general relativistic limits to mass, compactness, and spin rates is made. We consider observations made not only with photons, ranging from radio waves to X-rays, but also those involving neutrinos and gravity waves. We detail how precision determinations of structural properties would lead to significant restrictions on the poorly understood equation of state near and beyond the equilibrium density of nuclear matter.
854 citations
"Delayed neutrino-driven supernova e..." refers methods in this paper
...In case of the LS-EoS the maximum gravitational mass is 1.84 M⊙, whereas it is 2.21 M⊙ for the HW-EoS, which are both compatible with measured neutron star masses (Lattimer & Prakash 2007)....
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