Central Density Effects on
White Dwarf Supernovae


Astronomy research
  Software Infrastructure:
     My instruments
  White dwarf supernova:
     Stable nickel production
     Remnant metallicities
     Colliding white dwarfs
     Merging white dwarfs
     Ignition conditions
     Metallicity effects
     Central density effects
     Detonation density effects
     Tracer particle burning
     Subsonic burning fronts
     Supersonic burning fronts
     W7 profiles
  Massive star supernova:
     Rotating progenitors
     3D evolution
     26Al & 60Fe
     44Ti, 60Co & 56Ni
     Yields of radionuclides
     Effects of 12C +12C
     SN 1987A light curve
     Constraints on Ni/Fe ratios
     An r-process
  Neutron Stars and Black Holes:
     Black Hole mass spectrum
     Compact object IMF
     He burn on neutron stars
     Variable white dwarfs
     Pop III with JWST
     Neutrino HR diagram
     Monte Carlo massive stars
     Pre-supernova neutrinos
     Pre-supernova variations
     Monte Carlo white dwarfs
     SAGB stars
     Nugrid Yields I
     Classical novae
     He shell convection
     Presolar grains
     BBFH at 40 years
  Chemical Evolution:
     Iron Pseudocarbynes
     Radionuclides in the 2020s
     Hypatia catalog
     Zone models H to Zn
     Mixing ejecta
     γ-rays within 100 Mpc
  Thermodynamics & Networks
     Stellar EOS
     12C(α,γ)16O Rate
     Proton-rich NSE
     Reaction networks
     Bayesian reaction rates
  Verification Problems:
     Validating an astro code
Software instruments
cococubed YouTube
Bicycle adventures
Public Outreach
Education materials
2022 ASU Solar Systems Astronomy
2022 ASU Energy in Everyday Life

AAS Journals
AAS YouTube
2022 Earendel, A Highly Magnified Star
2022 TV Columbae, Micronova
2022 White Dwarfs and 12C(α,γ)16O
2022 MESA VI
2022 MESA in Don't Look Up
2022 MESA Marketplace
2012-2023 MESA Schools
2022 MESA Classroom
2021 Bill Paxton, Tinsley Prize

Contact: F.X.Timmes
my one page vitae,
full vitae,
research statement, and
teaching statement.

Evaluating Systematic Dependencies Of Type Ia Supernovae: The Influence Of Central Density (2012)
In this article we present a study exploring a systematic effect on the brightness of Type Ia supernovae using numerical models that assume the single-degenerate paradigm. Our investigation varied the central density of the progenitor white dwarf at flame ignition, and considered its impact on the explosion yield, particularly the production and distribution of radioactive $^{56}$Ni, which powers the light curve. We performed a suite of two-dimensional simulations with randomized initial conditions, allowing us to characterize the statistical trends that we present. The simulations indicate that the production of Fe-group material is statistically independent of progenitor central density, but the mass of stable Fe-group isotopes is tightly correlated with central density, with a decrease in the production of $^{56}$Ni at higher central densities.

These results imply that progenitors with higher central densities produce dimmer events. We provide details of the post-explosion distribution of $^{56}$Ni in the models, including the lack of a consistent centrally located deficit of $^{56}$Ni, which may be compared to observed remnants. By performing a self-consistent extrapolation of our model yields and considering the main-sequence lifetime of the progenitor star and the elapsed time between the formation of the white dwarf and the onset of accretion, we develop a brightness-age relation that improves our prediction of the expected trend for single degenerates and we compare this relation with observations.

image image
image image
image image

On Variations Of The Brightness Of Type Ia Supernovae With The Age Of The Host Stellar Population (2010)
Recent observational studies of type Ia supernovae (SNeIa) suggest correlations between the peak brightness of an event and the age of the progenitor stellar population. This trend likely follows from properties of the progenitor white dwarf (WD), such as central density, that follow from properties of the host stellar population.

letter we present a statistically well-controlled, systematic study utilizing a suite of multi-dimensional SNeIa simulations investigating the influence of central density of the progenitor WD on the production of Fe-group material, particularly radioactive $^{56}$Ni, which powers the light curve. We find that on average, as the progenitor's central density increases, production of Fe-group material does not change but production of $^{56}$Ni decreases. We attribute this result to a higher rate of neutronization at higher density. The central density of the progenitor is determined by the mass of the WD and the cooling time prior to the onset of mass transfer from the companion, as well as the subsequent accretion heating and neutrino losses. The dependence of this density on cooling time, combined with the result of our central density study, offers an explanation for the observed age-luminosity correlation: a longer cooling time raises the central density at ignition thereby producing less $^{56}$Ni and thus a dimmer event. While our ensemble of results demonstrates a significant trend, we find considerable variation between realizations, indicating the necessity for averaging over an ensemble of simulations to demonstrate a statistically significant result.