Showing papers by "Hans-Thomas Janka published in 2023"
27 Jan 2023
TL;DR: In this article , the impact of small-scale flavor conversions of neutrinos, the so-called fast flavor conversions (FFCs), on the dynamical evolution and neutrino emission of core-collapse supernovae (CCSNe) was explored.
Abstract: We explore the impact of small-scale flavor conversions of neutrinos, the so-called fast flavor conversions (FFCs), on the dynamical evolution and neutrino emission of core-collapse supernovae (CCSNe). In order to do that, we implement FFCs in the spherically symmetric (1D) CCSN simulations of a 20 solar-mass progenitor model parametrically, assuming that FFCs happen at densities lower than a systematically varied threshold value and lead to an immediate flavor equilibrium consistent with lepton number conservation. We find that besides hardening the electron neutrino and antineutrino spectra, which helps the expansion of the shock by enhanced postshock heating, FFCs can cause significant, nontrivial modifications of the energy transport in the SN environment via increasing the heavy-lepton neutrino luminosities. In our non-exploding models this results in extra cooling of the layers around the neutrinospheres, which triggers a faster contraction of the proto-neutron star and hence, in our 1D models, hampers the CCSN explosion. Although our study is limited by the 1D nature of our simulations, it provides valuable insights into how neutrino flavor conversions in the deepest CCSN regions can impact the neutrino release and the corresponding response of the stellar medium.
7 citations
TL;DR: ExtraSS as discussed by the authors is a simulator for generating 3D spectra for supernovae in the nebular phase by using modern multi-dimensional explosion models as input, which can be used to calculate the energy deposition from the radioactive decay of 56Ni → 56Co → 56Fe and uses this to determine the non-local thermal equilibrium temperature, excitation and ionization structure across the nebula.
Abstract:
We present ExTraSS (EXplosive TRAnsient Spectral Simulator), a newly developed code aimed at generating 3D spectra for supernovae in the nebular phase by using modern multi-dimensional explosion models as input. It is well established that supernovae are asymmetric by nature, and that the morphology is encoded in the line profiles during the nebular phase, months after the explosion. In this work, we use ExTraSS to study one such simulation of a 3.3 M⊙ He-core explosion (Mejecta = 1.3 M⊙, Ekin = 1.05 × 1051 erg) modelled with the Prometheus-HotB code and evolved to the homologous phase. Our code calculates the energy deposition from the radioactive decay of 56Ni → 56Co → 56Fe and uses this to determine the Non-Local-Thermodynamic-Equilibrium temperature, excitation and ionization structure across the nebula. From the physical condition solutions we generate the emissivities to construct spectra depending on viewing angles. Our results show large variations in the line profiles with viewing angles, as diagnosed by the first three moments of the line profiles; shifts, widths, and skewness. We compare line profiles from different elements, and study the morphology of line-of-sight slices that determine the flux at each part of a line profile. We find that excitation conditions can sometimes make the momentum vector of the ejecta emitting in the excited states significantly different from that of the bulk of the ejecta of the respective element, thus giving blueshifted lines for bulk receding material, and vice versa. We compare the 3.3 M⊙ He-core model to observations of the Type Ib supernova SN 2007Y.
18 May 2023
TL;DR: In this paper , the first simulations of core-collapse supernovae (CCSNe) in axial symmetry (2D) with feedback from fast neutrino flavor conversion (FFC) were presented.
Abstract: We present the first simulations of core-collapse supernovae (CCSNe) in axial symmetry (2D) with feedback from fast neutrino flavor conversion (FFC). Our schematic treatment of FFCs assumes instantaneous flavor equilibration under the constraint of lepton-number conservation. Systematically varying the spatial domain where FFCs are assumed to occur, we find that they facilitate SN explosions in low-mass (9-12 solar masses) progenitors that otherwise explode with longer time delays, whereas FFCs weaken the tendency to explode of higher-mass (around 20 solar masses) progenitors.
19 Jun 2023
TL;DR: In this paper , the final collapse of rotating and non-rotating very massive star progenitors with zero-age main-sequence masses of 60, 80, and 115 was studied by 2D hydrodynamics simulations.
Abstract: We study the final collapse of rotating and non-rotating very massive star progenitors with zero-age-main-sequence masses of 60, 80, and 115 $\mathrm{M}_\odot$ by 2D hydrodynamics simulations. The general relativistic radiation hydrodynamics code NADA-FLD allows us to follow the evolution beyond the moment when the newly born neutron star (NS) collapses to a black hole (BH), which happens within 350-580 ms after bounce in all cases. In all cases except the rapidly rotating 60$\mathrm{M}_\odot$ model, neutrino heating leads to shock revival. In the rapidly rotating 60 $\mathrm{M}_\odot$ model, centrifugal effects support higher NS mass but reduce the radiated neutrino luminosities and mean energies, and the value of neutrino-heating rate is smaller by roughly a factor of two compared to its non-rotating counterpart. After BH formation, the neutrino luminosities drop steeply but continue on a 1-2 orders of magnitude lower level for several 100\,ms because of aspherical accretion of neutrino and shock-heated matter. In all shock-reviving models BH accretion swallows the entire neutrino-heated matter and the explosion energies decrease from maxima to zero within a few seconds latest. Nevertheless, the shock or a sonic pulse moves outward and may trigger mass loss, which we estimate by long-time simulations with the Prometheus code.