The toroidal iron atmosphere of a protoneutron star: Numerical solution

Abstract

A numerical method presented by Imshennik et al. (2002) is used to solve the twodimensional axisymmetric hydrodynamic problem on the formation of a toroidal atmosphere during the collapse of an iron stellar core and outer stellar layers. An evolutionary model from Boyes et al. (1999) with a total mass of 25M ⊙ is used as the initial data for the distribution of thermodynamic quantities in the outer shells of a high-mass star. Our computational region includes the outer part of the iron core (without its central part with a mass of 1M ⊙ that forms the embryo of a protoneutron star at the preceding stage of the collapse) and the silicon and carbon-oxygen shells with a total mass of (1.8-2.5)M ⊙ . We analyze in detail the results of three calculations in which the difference mesh and the location of the inner boundary of the computational region are varied. In the initial data, we roughly specify an angular velocity distribution that is actually justified by the final result-the formation of a hydrostatic equilibrium toroidal atmosphere with reasonable total mass, M tot = (0.117-0.122)M ⊙ , and total angular momentum, J tot = (0.445-0.472) × 10 50 erg s, for the two main calculations. We compare the numerical solution with our previous analytical solution in the form of toroidal atmospheres (Imshennik and Manukovskii 2000). This comparison indicates that they are identical if we take into account the more general and complex equation of state with a nonzero temperature and self-gravitation effects in the atmosphere. Our numerical calculations, first, prove the stability of toroidal atmospheres on characteristic hydrodynamic time scales and, second, show the possibility of sporadic fragmentation of these atmospheres even after a hydrodynamic equilibrium is established. The calculations were carried out under the assumption of equatorial symmetry of the problem and up to relatively long time scales (∼10 s). c 2003 MAIK "Nauka/Interperiodica".

The barium isotopic fractions in five metal-poor stars

“…There are many candidates for r-process sites including neutron star explosions (Imshennik 1992), neutron star surface explosions (Bisnovatyi-Kogan & Chechetkin 1979) and neutron star winds (Panov & Janka 2009;Wanajo et al 2001), to name a few. However, presently the most favoured sites for the r-process are core-collapse supernovae .…”

asymmetric collapsing supernovae explosion with rotation

“…The formation of a toroidal structure in the vicinity of a proto-neutron star obtained in the numerical simulation is considered to be the main result of the study [6]. This process prevents the accretion of the stellar envelope on the central compact object.…”

“…The formulation of the problem on the formation of a toroidal structure was itself largely reinforced by the existence of analytical solution to the hydrostatic equilibrium equations for a cool iron gas in the gravitational field of a proto-neutron star [7]. Numerical solution, first, shows the stability of such configuration of matter against two-dimensional perturbations and, second, removes several restrictions in the formulation of the analytical problem [7] due to the allowance for non-zero matter temperature and the effect of self-gravitation.…”

“…Numerical solution, first, shows the stability of such configuration of matter against two-dimensional perturbations and, second, removes several restrictions in the formulation of the analytical problem [7] due to the allowance for non-zero matter temperature and the effect of self-gravitation.…”

Experiments with probe masses

“…Thus, the expected sensitivity in Advanced LIGO will be close to the SQL. Advanced LIGO will start to operate within 7 years, and the community of physicists may expect to obtain qualitatively new information, in particular: (i) the estimate of the population of neutron stars in the Metagalaxy and, consequently, the contribution of these stars to dark matter; (ii) the shape of gravitational burst from neutron stars may indicate which equation of state (from the existing list) would hold for neutron star matter; (iii) the analysis of signal shape from black holes merging may permit the general relativity testing in the ultrarelativistic case (where the relative difference between the gravitational potential and c 2 is much less than unity); and (iv) a test of the prediction made by V. Imshennik and I. Popov (20) that supernova birth is a nonsymmetric event.…”