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Register a new userOn The Development of Multidimensional Progenitor Models For Core-collapse Supernovae
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Multidimensional hydrodynamic simulations of shell convection in massive stars suggest the development of aspherical perturbations that may be amplified during iron core-collapse. These perturbations have a crucial and qualitative impact on the delayed neutrino-driven core-collapse supernova explosion mechanism by increasing the total stress behind the stalled shock. In this paper, we investigate the properties of a 15 msun model evolved in 1-,2-, and 3-dimensions (3D) for the final $sim$424 seconds before gravitational instability and iron core-collapse using MESA and the FLASH simulation framework. We find that just before collapse, our initially perturbed fully 3D model reaches angle-averaged convective velocity magnitudes of $approx$ 240-260 km s$^{-1}$ in the Si- and O-shell regions with a Mach number $approx$ 0.06. We find the bulk of the power in the O-shell resides at large scales, characterized by spherical harmonic orders ($ell$) of 2-4, while the Si-shell shows broad spectra on smaller scales of $ellapprox30-40$. Both convective regions show an increase in power at $ell=5$ near collapse. We show that the 1D texttt{MESA} model agrees with the convective velocity profile and speeds of the Si-shell when compared to our highest resolution 3D model. However, in the O-shell region, we find that texttt{MESA} predicts speeds approximately emph{four} times slower than all of our 3D models suggest. All eight of the multi-dimensional stellar models considered in this work are publicly available.
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We investigate core-collapse supernova (CCSN) nucleosynthesis in polar axisymmetric simulations using the multidimensional radiation hydrodynamics code CHIMERA. Computational costs have traditionally constrained the evolution of the nuclear composition in CCSN models to, at best, a 14-species $alpha$-network. Such a simplified network limits the ability to accurately evolve detailed composition, neutronization and the nuclear energy generation rate. Lagrangian tracer particles are commonly used to extend the nuclear network evolution by incorporating more realistic networks in post-processing nucleosynthesis calculations. Limitations such as poor spatial resolution of the tracer particles, estimation of the expansion timescales, and determination of the mass-cut at the end of the simulation impose uncertainties inherent to this approach. We present a detailed analysis of the impact of these uncertainties on post-processing nucleosynthesis calculations and implications for future models.
Using resolved stellar photometry measured from archival HST imaging, we generate color-magnitude diagrams of the stars within 50 pc of the locations of historic core-collapse supernovae that took place in galaxies within 8 Mpc. We fit these color-magnitude distributions with stellar evolution models to determine the best-fit age distribution of the young population. We then translate these age distributions into probability distributions for the progenitor mass of each SNe. The measurements are anchored by the main-sequence stars surrounding the event, making them less sensitive to assumptions about binarity, post-main-sequence evolution, or circumstellar dust. We demonstrate that, in cases where the literature contains masses that have been measured from direct imaging, our measurements are consistent with (but less precise than) these measurements. Using this technique, we constrain the progenitor masses of 17 historic SNe, 11 of which have no previous estimates from direct imaging. Our measurements still allow the possibility that all SNe progenitor masses are <20 M_sun. However, the large uncertainties for the highest-mass progenitors also allow the possibility of no upper-mass cutoff.
We age-date the stellar populations associated with 12 historic nearby core-collapse supernovae (CCSNe) and 2 supernova impostors, and from these ages, we infer their initial masses and associated uncertainties. To do this, we have obtained new HST imaging covering these CCSNe. Using these images, we measure resolved stellar photometry for the stars surrounding the locations of the SNe. We then fit the color-magnitude distributions of this photometry with stellar evolution models to determine the ages of any young existing populations present. From these age distributions, we infer the most likely progenitor mass for all of the SNe in our sample. We find ages between 4 and 50 Myr, corresponding to masses from 7.5 to 59 solar masses. There were no SNe that lacked a young population within 50~pc. Our sample contains 4 type Ib/c SNe; their masses have a wide range of values, suggesting that the progenitors of stripped-envelope SNe are binary systems. Both impostors have masses constrained to be $lesssim$7.5 solar masses. In cases with precursor imaging measurements, we find that age-dating and precursor imaging give consistent progenitor masses. This consistency implies that, although the uncertainties for each technique are significantly different, the results of both are reliable to the measured uncertainties. We combine these new measurements with those from our previous work and find that the distribution of 25 core-collapse SNe progenitor masses is consistent with a standard Salpeter power-law mass function, no upper mass cutoff, and an assumed minimum mass for core-collapse of 7.5~M$_{odot}$.
We analyze the properties of 42 rapidly rotating, low metallicity, quasi-chemically homogeneously evolving stellar models in the mass range between 4 and 45 $,mathrm{M}_odot$ at the time of core collapse. Such models were proposed as progenitors for both superluminous supernovae (SLSNe) and long duration gamma-ray bursts (lGRBs), and the Type Ic-BL supernovae (SNe) that are associated with them. Our findings suggest that whether these models produce a magnetar driven SLSN explosion or a near-critically rotating black hole (BH) is not a monotonic function of the initial mass. Rather, their explodability varies non-monotonically depending on the late core evolution, once chemical homogeneity is broken. Using different explodability criteria we find that our models have a clear preference to produce SLSNe at lower masses, and lGRBs at higher masses; but find several exceptions, expecting lGRBs to form from stars as low as 10 $,mathrm{M}_odot$, and SLSNe with progenitors as massive as 30 $,mathrm{M}_odot$. In general, our models reproduce the predicted angular momenta, ejecta masses and magnetic field strengths at core collapse inferred for SLSNe and lGRBs, and suggest significant interaction with their circumstellar medium, particularly for explosions with low ejecta mass.
We present self-consistent, axisymmetric core-collapse supernova simulations performed with the Prometheus-Vertex code for 18 pre-supernova models in the range of 11-28 solar masses, including progenitors recently investigated by other groups. All models develop explosions, but depending on the progenitor structure, they can be divided into two classes. With a steep density decline at the Si/Si-O interface, the arrival of this interface at the shock front leads to a sudden drop of the mass-accretion rate, triggering a rapid approach to explosion. With a more gradually decreasing accretion rate, it takes longer for the neutrino heating to overcome the accretion ram pressure and explosions set in later. Early explosions are facilitated by high mass-accretion rates after bounce and correspondingly high neutrino luminosities combined with a pronounced drop of the accretion rate and ram pressure at the Si/Si-O interface. Because of rapidly shrinking neutron star radii and receding shock fronts after the passage through their maxima, our models exhibit short advection time scales, which favor the efficient growth of the standing accretion-shock instability. The latter plays a supportive role at least for the initiation of the re-expansion of the stalled shock before runaway. Taking into account the effects of turbulent pressure in the gain layer, we derive a generalized condition for the critical neutrino luminosity that captures the explosion behavior of all models very well. We validate the robustness of our findings by testing the influence of stochasticity, numerical resolution, and approximations in some aspects of the microphysics.
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