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A fundamental issue in star formation is understanding the precise mechanisms leading to the formation of prestellar cores, and their subsequent gravitationally unstable evolution. To address this question, we carefully construct a suite of…
Gravitational waves (GWs) hold great potential for an unobscured view of protoneutron stars (PNSs) formed as a result of stellar collapses. While waiting for discovery, deepening the understanding of GW emission in theory is beneficial for…
We present numerical results on two- (2D) and three-dimensional (3D) hydrodynamic core-collapse simulations of an 11.2$M_\odot$ star. By changing numerical resolutions and seed perturbations systematically, we study how the postbounce…
Despite the sphericity of the collapsing stellar core, the birth conditions of neutron stars can be highly non spherical due to a hydrodynamical instability of the shocked accretion flow. Here we report the first laboratory experiment of a…
We study the gravitational collapse of a rotating supermassive star (SMS) by means of a (3+1) hydrodynamical simulation in a post-Newtonian (PN) approxi- mation of general relativity. This problem is particularly challenging because of the…
In this Letter, we report the outcomes of 1-D modelling of a rotating 25 M$_{\odot}$ zero-age main-sequence Population III star up to the stage of the onset of core collapse. Rapidly rotating models display violent and sporadic mass losses…
Traditional models of core collapse suggest the issue of successful versus failed supernova explosions and neutron star versus black hole formation depends monotonically on the mass (and metallicity) of the progenitor star. Here we argue…
We found that loosely wound spiral shocks in an isothermal gas disk caused by a non-axisymmetric potential are hydrodynamically unstable, if the shocks are strong enough. High resolution, global hydrodynamical simulations using three…
In certain mass ranges, massive stars can undergo a violent pulsation triggered by the electron/positron pair instability that ejects matter, but does not totally disrupt the star. After one or more of these pulsations, such stars are…
It has been estimated that a significant proportion of binary neutron star merger events produce long-lived massive remnants supported by differential rotation and subject to rotational instabilities. To examine formation and oscillation of…
The present study of the two-stream instability in stellar disks with counter-rotating components of stars and/or gas is stimulated by recently discovered counter-rotating spiral and S0 galaxies. Strong linear two-stream instability of…
We investigate the impact of rotation and magnetic fields on the dynamics and gravitational wave emission in 2D core-collapse supernova simulations with neutrino transport. We simulate 17 different models of $15\,M_\odot$ and $39\,M_\odot$…
We present the first calculation of gravitational wave emission produced in the gravitational collapse of uniformly rotating neutron stars to black holes in fully three-dimensional simulations. The initial stellar models are relativistic…
The spiral core instability, observed in large aspect ratio Rayleigh-Benard convection, is studied numerically in the framework of the Swift-Hohenberg equation coupled to a large-scale flow. It is shown that the instability leads to…
We present numerical results on the hydrodynamic stability of coalescing binary stars in the first post Newtonian(1PN) approximation of general relativity. We pay particular attention to the hydrodynamical instability of corotating binary…
We present new results on instabilities in rapidly and differentially rotating neutron stars. We model the stars in full general relativity and describe the stellar matter adopting a cold realistic equation of state based on the unified SLy…
We use numerical hydrodynamic simulations to investigate prestellar core formation in the dynamic environment of giant molecular clouds, focusing on planar post-shock layers produced by colliding turbulent flows. A key goal is to test how…
We study the explosion mechanism of collapse-driven supernovae by numerical simulations with a new nuclear EOS based on unstable nuclei. We report new results of simulations of general relativistic hydrodynamics together with the Boltzmann…
We performed 2D, axisymmetric, MHD simulations with Cosmos++ in order to examine the growth of the magnetorotational instability (MRI) in core--collapse supernovae. We have initialized a non--rotating 15 solar mass progenitor, infused with…
Non-spherical structure in massive stars at the point of iron core collapse can have a qualitative impact on the properties of the ensuing core-collapse supernova explosions and the multi-messenger signals they produce. Strong perturbations…