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Astronomy Reports - A large fraction of the energy released during the gravitational collapse of the core of a massive star is carried by neutrinos. Neutrinos play the main role in explaining... 相似文献
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I. V. Baikov V. M. Suslin V. M. Chechetkin V. Bychkov L. Stenflo 《Astronomy Reports》2007,51(4):274-281
We propose a new mechanism for type II supernova explosions. An important element of the model is large-scale convection that arises due to non-equilibrium neutronization of the matter in the central region of the proto-neutron star. Our analytical estimates and numerical simulations of the convection rate are in good mutual agreement. Large-scale convection leads to the rapid transport of neutrinos from the center of the star to the bounce shock formed during the pause in the collapse of the stellar matter in the proto-neutron star. The mean neutrino energy is 30–50 MeV. We analyze the dependence of the mean neutrino energy on the size of the convection cells—“bubbles.” Our computations of the interaction between the neutrinos and the shock show that the velocity of the shock along the rotational axis of the star exceeds the escape velocity. Thus, explosion of the envelope and a supernova with a very asymmetrical envelope structure become possible, leading to the formation of a neutron star. 相似文献
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Neutrino transfer via convective flow to the surface of a proto-neutron star is numerically simulated. The evolution of the neutrino distribution in a heated region rising from the center of the proto-neutron star to its surface is simulated using a kinetic equation with a Uehling-Uhlenbeck collision integral in a uniform, isotropic approximation. The composition of the matter in the region under consideration changes due to the “burning” of electrons and protons by beta processes. The simulation results enable the estimation of the characteristic time required for the rising medium to become optically thin to neutrinos and the characteristic spectrum of the neutrinos that are emitted. 相似文献
4.
Numerical simulations of gas-dynamical processes taking place in the accretion disk of a stellar binary system are presented. The initial state of the disk is an equilibrium gaseous configuration. Mechanisms for the development of spiral waves and associated variations in the angular momentum of the gas are considered. The influence of the ratio of the binary-component masses and the initial disk configuration are investigated. It is concluded that the existence of a steady-state disk is impossible without a flow of gas from the donor star. 相似文献
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Pascal Chardonnet Valery Chechetkin Lev Titarchuk 《Astrophysics and Space Science》2010,325(2):153-161
We present a model of a gamma-ray burst (GRB) related to “very massive” stars. In the framework of our model, the GRB phenomenon
is a result of helium burning in degenerate conditions in a massive star (≳130 M
⊙), in which the thermal nuclear burning occurs in the deflagration regime and has a pulsating temporal pattern. The shock
runs away from the burning (reaction) zone, which leads to the development of a coronal outflow (jet-like) structure. In our
scenario the GRB observable prompt fast rise and decay part can be a result of photon propagation through the hot corona (Comptonization
photosphere) of the star. On the other hand, the GRB afterglow is a cooling phase of the expanding and outflowing envelope.
Presumably, the X-ray part of the GRB emergent spectrum is formed due to upscattering of soft photons of outer layers of the
star off hot coronal electrons, and thus it should have a specific shape of the Comptonization spectrum. 相似文献
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The aim of this study is to investigate the accretion of matter onto a compact gravitating remnant (neutron star) in the central region of the expanding shell of a Type II supernova. Computations of an explosion with the energetics of a Type II supernova have been performed to derive the structure of matter in the vicinity of the neutron star. The energy of the expanding shell and the parameters of the presupernova correspond to the known values for SN 1987A. This accretion leads to the formation of a layer of fairly dense and hot gas at the surface of the compact remnant, providing the conditions for nucleosynthesis reactions. Thus, one result of the study is to demonstrate the importance of the r and rbc processes, or explosive nucleosynthesis, in the compact envelope of a neutron star. A second result is the production of emission lines from unstable elements formed in the central part of the neutron-star envelope.
相似文献8.
We present a comparative study of the original metric of Schwarzschild and the metric introduced by Hilbert. The properties
of these metrics, as well as the Tolman metric for collapsing dust, are analyzed. 相似文献
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Our previous studies of large-scale vortical flows arising in shear flows of stellar accretion disks with Keplerian azimuthal velocity distributions as a result of the development of small perturbations are continued. The development of large-scale instability in an accretion disk is investigated via mathematical modeling. One result obtained is the change of the disk flow structure due to the formation of large vortices. In the limiting case, sufficiently long evolution leads to the formation of several asymmetric spiral structures of the flow of disk matter. The presence of large-scale structures leads to angular-momentum redistribution in the disk. 相似文献
10.
We have computed the ejection of a massive envelope by a star during a type II supernova explosion in the presence of a compact
remnant (a neutron star or black hole). This problem is of interest because of the possible presence of a compact remnant
following the SN 1987A explosion. The computations demonstrate that a fairly large amount of matter is left in the neighborhood
of the compact gravitating body. We present computations of the accretion rate onto the surface of the compact remnant. The
estimated luminosity exceeds that observed for SN 1987A in various frequency ranges by several orders of magnitude. 相似文献