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1. Core-collapse supernova neutrino emission and detection informed by state-of-the-art three-dimensional numerical models

   https://doi.org/10.1093/mnras/staa2691  

   Nagakura, Hiroki ; Burrows, Adam ; Vartanyan, David ; Radice, David ( November 2020 , Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT Based on our recent three-dimensional core-collapse supernova (CCSN) simulations including both exploding and non-exploding models, we study the detailed neutrino signals in representative terrestrial neutrino observatories, namely Super-Kamiokande (Hyper-Kamiokande), DUNE, JUNO, and IceCube. We find that the physical origin of difference in the neutrino signals between 1D and 3D is mainly proto-neutron-star convection. We study the temporal and angular variations of the neutrino signals and discuss the detectability of the time variations driven by the spiral standing accretion shock instability (spiral SASI) when it emerges for non-exploding models. In addition, we determine that there can be a large angular asymmetry in the event rate (${\gtrsim} 50 {{\ \rm per\ cent}}$), but the time-integrated signal has a relatively modest asymmetry (${\lesssim} 20 {{\ \rm per\ cent}}$). Both features are associated with the lepton-number emission self-sustained asymmetry and the spiral SASI. Moreover, our analysis suggests that there is an interesting correlation between the total neutrino energy (TONE) and the cumulative number of neutrino events in each detector, a correlation that can facilitate data analyses of real observations. We demonstrate the retrieval of neutrino energy spectra for all flavours of neutrino by applying a novel spectrum reconstruction technique to the data from multiple detectors. We find that this new method is capable of estimating the TONE within the error of ∼20 per cent if the distance to the CCSN is ≲6 kpc. 

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2. Characterizing the Directionality of Gravitational Wave Emission from Matter Motions within Core-collapse Supernovae

   https://doi.org/10.3847/1538-4357/acfca4  

   Pajkos, Michael A. ; VanCamp, Steven J. ; Pan, Kuo-Chuan ; Vartanyan, David ; Deppe, Nils ; Couch, Sean M. ( November 2023 , The Astrophysical Journal)

   We analyze the directional dependence of the gravitational wave (GW) emission from 15 3D neutrino radiation hydrodynamic simulations of core-collapse supernovae (CCSNe). Using spin weighted spherical harmonics, we develop a new analytic technique to quantify the evolution of the distribution of GW emission over all angles. We construct a physics-informed toy model that can be used to approximate GW distributions for general ellipsoid-like systems, and use it to provide closed form expressions for the distribution of GWs for different CCSN phases. Using these toy models, we approximate the protoneutron star (PNS) dynamics during multiple CCSN stages and obtain similar GW distributions to simulation outputs. When considering all viewing angles, we apply this new technique to quantify the evolution of preferred directions of GW emission. For nonrotating cases, this dominant viewing angle drifts isotropically throughout the supernova, set by the dynamical timescale of the PNS. For rotating cases, during core bounce and the following tens of milliseconds, the strongest GW signal is observed along the equator. During the accretion phase, comparable—if not stronger—GW amplitudes are generated along the axis of rotation, which can be enhanced by the lowT/∣W∣ instability. We show two dominant factors influencing the directionality of GW emission are the degree of initial rotation and explosion morphology. Lastly, looking forward, we note the sensitive interplay between GW detector site and supernova orientation, along with its effect on detecting individual polarization modes.

    

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3. The early evolution of magnetar rotation – II. Rapidly rotating magnetars: implications for gamma-ray bursts and superluminous supernovae

   https://doi.org/10.1093/mnras/stad2948  

   Prasanna, Tejas ; Coleman, Matthew S. B. ; Raives, Matthias J. ; Thompson, Todd A. ( September 2023 , Monthly Notices of the Royal Astronomical Society)

   Rapidly rotating magnetars have been associated with gamma-ray bursts (GRBs) and superluminous supernovae (SLSNe). Using a suite of two-dimensional magnetohydrodynamic simulations at fixed neutrino luminosity and a couple of evolutionary models with evolving neutrino luminosity and magnetar spin period, we show that magnetars are viable central engines for powering GRBs and SLSNe. We also present analytical estimates of the energy outflow rate from the proto-neutron star (PNS) as a function of polar magnetic field strength B0, PNS angular velocity Ω⋆, PNS radius R⋆, and mass outflow rate $\dot{M}$. We show that rapidly rotating magnetars with spin periods P⋆ ≲ 4 ms and polar magnetic field strength B0 ≳ 1015 G can release 1050 to 5 × 1051 erg of energy during the first ∼2 s of the cooling phase. Based on this result, it is plausible that sustained energy injection by magnetars through the relativistic wind phase can power GRBs. We also show that magnetars with moderate field strengths of B0 ≲ 5 × 1014 G do not release a large fraction of their rotational kinetic energy during the cooling phase and, hence, are not likely to power GRBs. Although we cannot simulate to times greater than ∼3–5 s after a supernova, we can hypothesize that moderate field strength magnetars can brighten the supernova light curves by releasing their rotational kinetic energy via magnetic dipole radiation on time-scales of days to weeks, since these do not expend most of their rotational kinetic energy during the early cooling phase.

    

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4. Inferring Type II-P Supernova Progenitor Masses from Plateau Luminosities

   https://doi.org/10.3847/2041-8213/acb052  

   Barker, Brandon L. ; O’Connor, Evan P. ; Couch, Sean M. ( February 2023 , The Astrophysical Journal Letters)

   Connecting observations of core-collapse supernova explosions to the properties of their massive star progenitors is a long-sought, and challenging, goal of supernova science. Recently, Barker et al. presented bolometric light curves for a landscape of progenitors from spherically symmetric neutrino-driven core-collapse supernova (CCSN) simulations using an effective model. They find a tight relationship between the plateau luminosity of the Type II-P CCSN light curve and the terminal iron-core mass of the progenitor. Remarkably, this allows us to constrain progenitor properties with photometry alone. We analyze a large observational sample of Type II-P CCSN light curves and estimate a distribution of iron-core masses using the relationship of Barker et al. The inferred distribution matches extremely well with the distribution of iron-core masses from stellar evolutionary models and namely, contains high-mass iron cores that suggest contributions from very massive progenitors in the observational data. We use this distribution of iron-core masses to infer minimum and maximum masses of progenitors in the observational data. Using Bayesian inference methods to locate optimal initial mass function parameters, we find$M_{\min }={9.8}_{-0.27}^{+0.37}$and$M_{\max }={24.0}_{-1.9}^{+3.9}$solar masses for the observational data.

    

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5. Effects of Different Closure Choices in Core-collapse Supernova Simulations

   https://doi.org/10.3847/1538-4357/aca75c  

   Wang, Tianshu ; Burrows, Adam ( January 2023 , The Astrophysical Journal)

   The two-moment method is widely used to approximate the full neutrino transport equation in core-collapse supernova (CCSN) simulations, and different closures lead to subtle differences in the simulation results. In this paper, we compare the effects of closure choices on various physical quantities in 1D and 2D time-dependent CCSN simulations with our multigroup radiation hydrodynamics code Fornax. We find that choices of the third-order closure relations influence the time-dependent simulations only slightly. Choices of the second-order closure relation have larger consequences than choices of the third-order closure, but these are still small compared to the remaining variations due to ambiguities in some physical inputs such as the nuclear equation of state. We also find that deviations in Eddington factors are not monotonically related to deviations in physical quantities, which means that simply comparing the Eddington factors does not inform one concerning which closure is better.

    

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