moon_sleep150.gif
Cococubed.com


Constraints on Ni/Fe Ratios

Home

Astronomy research
  Software Infrastructure:
     MESA
     FLASH
     STARLIB
     MESA-Web
     starkiller-astro
     My instruments
  White dwarf supernova:
     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
     Compact object IMF
  Stars:
     Neutrino HR diagram
     Pulsating white dwarfs
     Pop III with JWST
     Monte Carlo massive stars
     Neutrinos from pre-SN
     Pre-SN variations
     Monte Carlo white dwarfs
     SAGB stars
     Classical novae
     He shell convection
     Presolar grains
     He burn on neutron stars
     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
     Su-Olson
     Cog8
     Mader
     RMTV
     Sedov
     Noh
Software instruments
Presentations
Illustrations
cococubed YouTube
Bicycle adventures
Public Outreach
Education materials

AAS Journals
AAS YouTube
2020 Celebration of Margaret Burbidge
2020 Digital Infrastructure
2021 MESA Marketplace
2021 MESA Summer School
2021 ASU Solar Systems
2021 ASU Energy in Everyday Life


Contact: F.X.Timmes
my one page vitae,
full vitae,
research statement, and
teaching statement.
Constraints on explosive silicon burning in core-collapse supernovae from measured Ni/Fe ratios (2015)

Measurements of explosive nucleosynthesis yields in core-collapse supernovae provide tests for explosion models. In this article, we investigate constraints on explosive conditions derivable from measured amounts of nickel and iron after radioactive decays using nucleosynthesis networks with parameterized thermodynamic trajectories.

The Ni/Fe ratio is for most regimes dominated by the production ratio of $^{58}$Ni / ($^{54}$Fe + $^{56}$Ni), which tends to grow with higher neutron excess and with higher entropy. For SN 2012ec, a supernova that produced a Ni/Fe ratio of 3.4 $\pm$ 1.2 times solar, we find that burning of a fuel with neutron excess η ≈ 0.006 is required. Unless the progenitor metallicity is over 5 times solar, the only layer in the progenitor with such a neutron excess is the silicon shell. Supernovae producing large amounts of stable nickel thus suggest that this deep-lying layer can be, at least partially, ejected in the explosion. We find that common spherically symmetric models of MZAMS $\le$ 13 M$_{\odot}$ stars exploding with a delay time of less than one second (Mcut $<$; 1.5 M$_{\odot}) are able to achieve such silicon-shell ejection. Supernovae that produce solar or sub-solar Ni/Fe ratios, such as SN 1987A, must instead have burnt and ejected only oxygen-shell material, which allows a lower limit to the mass cut to be set.

Finally, we find that the extreme Ni/Fe value of 60-75 times solar derived for the Crab cannot be reproduced by any realistic-entropy burning outside the iron core, and neutrino-neutronization obtained in electron-capture models remain the only viable explanation.


image image
image image
image
$^{56}$Ni for Ye=0.490
image
$^{54}$Fe for Ye=0.490
image
$^{58}$Ni for Ye=0.490
image
$^{4}$He for Ye=0.490
image image
image image