We discuss results of 2D simulations of magnetorotational(MR) mechanism of core collapse supernova explosions. Due to the nonuniform collapse the collapsed core rotates differentially. In the presence of initial poloidal magnetic field its toroidal component appears and grows with time. Increased magnetic pressure leads to foramtion of compression wave which moves outwards. It transforms into the fast MHD shock wave (supernova shock wave). The shape of the MR supernova explosion qualitatively depends on the configuration of the initial magnetic field. For the dipole-like initial magnetic field the supernova explosion develops mainly along rotational axis forming mildly collimated jet. Quadrupole-like initial magnetic field leads to the explosion developing mainly along equatorial plane. Magnetorotational instability was found in our simulations. The supernova explosion energy is growing with increase of the initial core mass and rotational energy of the core, and corresponds to the observational data.
We present results of 2D simulation of magnetorotational (MR) supernova accompanied by jet formation in the core collapse supernova explosion. Initial magnetic field used in the simulations has dipole-like symmetry. Contrary to the simulations of MR supernova with initial quadrupole-like magnetic field, where the matter was ejected mainly near the equatorial plane, in presence of the dipole-like initial magnetic field the supernova explosion is developing preferably along a rotational axis, and leads to formation of a protojet. We expect that protojet propagation through the envelope of the st…
We present the results of 2D simulations of the magnetorotational model of a supernova explosion. After the core collapse the core consists of rapidly a rotating proto-neutron star and a differentially rotating envelope. The toroidal part of the magnetic energy generated by the differential rotation grows linearly with time at the initial stage of the evolution of the magnetic field. The linear growth of the toroidal magnetic field is terminated by the development of magnetohydrodynamic instability, leading to drastic acceleration in the growth of magnetic energy. At the moment when the magnet…
Core-collapse supernovae are connected with formation of neutron stars. Part of the gravitation energy is transformed into the energy of the explosion, observed in SN II, SN Ib,c type supernovae. The mechanism of transformation is not simple, because the overwhelming majority of the energy is going into weakly interacting neutrino. The attempts to use this energy for the explosion were not successful during about 40 years of investigation. We consider the explosion mechanism in which the source of energy is the rotation, and magnetic field serves for the transformation of the rotation energy i…
We perform 2D numerical simulations of a magnetorotational explosion of a rotating magnetized gas cloud. We found that amplification of a toroidal magnetic field due to the differential rotation leads to a transformation of the part of the rotational energy of the cloud to the radial kinetic energy. Simulations have been made for 3 initial values of $ξ$ (the relation of magnetic energy to the gravitational energy of the cloud): $ξ=10^{-2},10^{-4},10^{-6}$. Part of the matter - $\sim 7%$ of the mass of the cloud ($\sim 3.3%$ of the final gravitational energy of the cloud) - gets radial kinetic …
We study magnetohydrodynamic (MHD) effects arising in the collapse of magnetized, rotating, massive stellar cores to proto-neutron stars (PNSs). We perform axisymmetric numerical simulations in full general relativity with a hybrid equation of state. The formation and early evolution of a PNS are followed with a grid of 2500 x 2500 zones, which provides better resolution than in previous (Newtonian) studies. We confirm that significant differential rotation results even when the rotation of the progenitor is initially uniform. Consequently, the magnetic field is amplified both by magnetic wind…
We report a current status of our radiation-magnetohydrodynamic code for the study of core-collapse supernovae. In this contribution, we discuss the accuracy of our newly developed numerical code by presenting the test problem in a static background model. We also present the application to the spherically symmetric core-collapse simulations. Since close comparison with the previously published models is made, we are now applying it for the study of magnetorotational core-collapse supernovae.
Models of SN driven galactic winds for ellipticals are presented. We assume that ellipticals formed at high redshift and suffered an intense burst of star formation. The role of supernovae of type II and Ia in the chemical enrichment and in triggering galactic winds is studied. In particular, several recipes for SN feed-back together with detailed nucleosynthesis prescriptions are considered. It is shown that SNe of type II have a dominant role in enriching the interstellar medium of elliptical galaxies whereas type Ia SNe dominate the enrichment and the energetics of the intracluster medium.
We solve for the local vertical structure of a thin accretion disk threaded by a poloidal magnetic field. The angular velocity deviates from the Keplerian value as a result of the radial Lorentz force, but is constant on magnetic surfaces. Angular momentum transport and energy dissipation in the disk are parametrized by an alpha-prescription, and a Kramers opacity law is assumed to hold. We also determine the stability of the equilibria with respect to the magnetorotational (or Balbus-Hawley) instability. If the magnetic field is sufficiently strong, stable equilibria can be found in which the…
We investigate the action of the magnetorotational instability (MRI) in the context of iron-core collapse. Exponential growth of the field on the rotation time scale by the MRI will dominate the linear growth process of field line "wrapping" with the same characteristic time. We examine a variety of initial rotation states, with solid body rotation or a gradient in rotational velocity, that correspond to models in the literature. A relatively modest value of the initial rotation, a period of ~ 10 s, will give a very rapidly rotating PNS and hence strong differential rotation with respect to th…
We continue our investigations of the magnetorotational collapse of stellar cores discussing simulations performed with a modified Newtonian gravitational potential that mimics general relativistic effects. The approximate TOV potential used in our simulations catches several features of fully relativistic simulations quite well. It is able to correctly reproduce the behavior of models which show a qualitative change both of the dynamics and the gravitational wave signal when switching from Newtonian to fully relativistic simulations. If this is not the case, the Newtonian and the approximate …
A series of numerical simulations on magnetorotational core-collapse supernovae are carried out. Dipole-like configurations which are offset northward are assumed for the initially strong magnetic fields together with rapid differential rotations. Aims of our study are to investigate effects of the offset magnetic field on magnetar kicks and on supernova dynamics. Note that we study a regime where the proto-neutron star formed after collapse has a large magnetic field strength approaching that of a ``magnetar'', a highly magnetized slowly rotating neutron star. As a result, equatorially-asymme…
A model of supernovae feedback during disc galaxy formation is developed. The model incorporates infall of cooling gas from a halo and outflow of hot gas from a multiphase interstellar medium and a self-regulated model for star formation. Hot gas is created by thermal evaporation of cold gas clouds in supernovae remnants, and criteria are derived to estimate the characteristic temperature and density of the hot component and hence the net mass outflow rate. A number of refinements of the model are investigated, including a simple model of a galactic fountain, the response of the cold component…
A toy model for gamma-ray burst-supernovae (GRB-SN) is discussed by considering the coexistence of baryon poor outflows from black holes (BHs) and a powerful spin-connection to surrounding disk, giving rise to consistent calorimetry as described by van Putten (2001a) in a variant of the Blandford-Znajek process (BZ, 1977). In this model the half-opening angle of the magnetic flux tube on the horizon is determined by the mapping relation between the angular coordinate on the BH horizon and the radial coordinate on the surrounding accretion disk. The GRB is powered by the baryon poor outflows in…
We consider a newly-born millisecond magnetar, focusing on its interaction with the dense stellar plasma in which it is initially embedded. We argue that the confining pressure and inertia of the surrounding plasma acts to collimate the magnetar's Poynting-flux-dominated outflow into tightly beamed jets and increases its magnetic luminosity. We propose this process as an essential ingredient in the magnetar model for gamma-ray burst and asymmetric supernova central engines. We introduce the ``pulsar-in-a-cavity'' as an important model problem representing a magnetized rotating neutron star ins…
A relatively modest value of the initial rotation of the iron core, a period of ~ 6-31 s, will give a very rapidly rotating protoneutron star and hence strong differential rotation with respect to the infalling matter. Under these conditions, a seed field is expected to be amplified by the MRI and to grow exponentially. Exponential growth of the field on the time scale Omega^{-1} by the magnetorotational instability (MRI) will dominate the linear growth process of field line "wrapping" with the same characteristic time. The shear is strongest at the boundary of the newly formed protoneutron st…
We here explore the effects of the SN explosions into the environment of star-forming galaxies like the Milky Way. Successive randomly distributed and clustered SNe explosions cause the formation of hot superbubbles that drive either fountains or galactic winds above the galactic disk, depending on the amount and concentration of energy that is injected by the SNe. In a galactic fountain, the ejected gas is re-captured by the gravitational potential and falls back onto the disk. From 3D nonequilibrium radiative cooling hydrodynamical simulations of these fountains, we find that they may reach …
We study the two-dimensional, time-dependent MHD of radiation-driven winds from luminous accretion disks initially threaded by a purely axial magnetic field. The radiation force is mediated primarily by spectral lines. We use ideal MHD to compute the evolution of Keplerian disks, varying the magnetic field strengths and the luminosity of the disk, the central accreting object or both. We find that the magnetic fields very quickly start deviating from purely axial due to the magnetorotational instability. This leads to fast growth of the toroidal magnetic field. As a result the toroidal field d…
The Kelvin-Helmholtz cooling epoch, lasting tens of seconds after the birth of a neutron star in a successful core-collapse supernova, is accompanied by a neutrino-driven wind. For magnetar-strength ($\sim10^{15}$ G) large scale surface magnetic fields, this outflow is magnetically-dominated during the entire cooling epoch.Because the strong magnetic field forces the wind to co-rotate with the protoneutron star,this outflow can significantly effect the neutron star's early angular momentum evolution, as in analogous models of stellar winds (e.g. Weber & Davis 1967). If the rotational energy is…
Outflows of pre-main-sequence stars drive shocks into molecular material within 0.01 - 1 pc of the young stars. The shock-heated gas emits infrared, millimeter and submillimeter lines of many species including. Dust grains are important charge carriers and play a large role in coupling the magnetic field and flow of neutral gas. Some effects of the dust on the dynamics of oblique shocks began to emerge in the 1990s. However, detailed models of these shocks are required for the calculation of the grain sputtering contribution to gas phase abundances of species producing observed emissions. We a…
We construct models of core-collapse supernovae in one spatial dimension, including rotation, angular momentum transport, and viscous dissipation employing an alpha-prescription. We compare the evolution of a fiducial 11 M_sun non-rotating progenitor with its evolution including a wide range of imposed initial rotation profiles (1.25<P_0<8 s, where P_0 is the initial, approximately solid-body, rotation period of the iron core). This range of P_0 covers the region of parameter space from where rotation begins to modify the dynamics (P_0~8 s) to where angular velocities at collapse approach Kepl…
We present a global magnetohydrodynamic (MHD) three dimensional simulation of a nonradiative accretion flow originating in a pressure supported torus. The evolution is controlled by the magnetorotational instability which produces turbulence. The flow forms a nearly Keplerian disk. The total pressure scale height in this disk is comparable to the vertical size of the initial torus. Gas pressure dominates only near the equator; magnetic pressure is more important in the surrounding atmosphere. A magnetically dominated bound outflow is driven from the disk. The accretion rate through the disk ex…
We investigate the generation of galactic outflows by supernova feedback in the context of SPH cosmological simulations. We use a modified version of the code GADGET-2 which includes chemical enrichment and energy feedback by Supernova. We find that energy feedback plays a fundamental role in the evolution of galaxies, heating up the cold material in the centre of the haloes and triggering outflows which efficiently transport gas from the centre to the outskirts of galaxies. The impact of feedback is found to depend on the virial mass of the system with smaller systems, such as dwarf galaxies,…
The relativistic outflows from gamma-ray bursts are now thought to be narrowly collimated into jets. After correcting for this jet geometry there is a remarkable constancy of both the energy radiated by the burst and the kinetic energy carried by the outflow. Gamma-ray bursts are still the most luminous explosions in the Universe, but they release energies that are comparable to supernovae. The diversity of cosmic explosions appears to be governed by the fraction of energy that is coupled to ultra-relativistic ejecta.
We examine metal and entropy content in galaxy groups having T_X~0.5-2 keV in cosmological hydrodynamic simulations. Our simulations include a well-constrained prescription for galactic outflows following momentum-driven wind scalings, and a sophisticated chemical evolution model. Our simulation with no outflows reproduces observed iron abundances in X-ray emitting gas, but the oxygen abundance is too low; including outflows yields iron and oxygen abundances in good agreement with data. X-ray measures of [O/Fe] primarily reflect metal distribution mechanisms into hot gas, not the ratio of Type…
We have used MERLIN, at 1.4 and 5 GHz, to search for radio supernovae (RSNe) and supernova remnants (SNRs) in the unobscured irregular dwarf galaxy NGC1569, and in particular in the region of its super star clusters (SSCs) A and B. Throughout NGC1569 we find some 5 RSNe and SNRs but the SSCs and their immediate surroundings are largely devoid of non-thermal radio sources. Even though many massive stars in the SSCs are expected to have exploded already, when compared with M82 and its many SSCs the absence of RSNe and SNRs in and near A and B may seem plausible on statistical arguments. The abse…
We suggest that part of the infalling material during the core-collapse of a massive star goes into orbit around the compact core to form a hot, dense, centrifugally-supported accretion disk whose evolution is strongly influenced by neutrino interactions. Under a wide range of conditions, this neutrino-dominated accretion flow will be advection-dominated and will develop a substantial outflowing wind. We estimate the energy carried out in the wind and find that it exceeds $10^{50}$ erg for a wide range of parameters and even exceeds 10^{51} erg for reasonable parameter choices. We propose that…
