Effects of 12C +12C


Astronomy research
  Software Infrastructure:
     My codes
  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
     Pop III JWST
     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:
     Hypatia catalog
     Zone models H to Zn
     Mixing ejecta
     γ-rays within 100 Mpc
  Thermodynamics & Networks
     Stellar EOS
     Reaction networks
     Proton-rich NSE
     Bayesian reaction rates
  Verification Problems:
     Validating an astro code
Software instruments
Bicycle adventures

AAS Journals
2017 MESA Marketplace
2017 MESA Summer School
2017 ASU+EdX AST111x
Teaching materials
Education and Public Outreach

Contact: F.X.Timmes
my one page vitae,
full vitae,
research statement, and
teaching statement.
The effect of 12C +12C rate uncertainties on the evolution and nucleosynthesis of massive stars - 2012
In this paper, we explore recent suggestions that the 12C +12C reaction rate may be higher than that currently used in stellar models. In order to investigate the effect of an enhanced carbon-burning rate on massive star structure and nucleosynthesis, new stellar evolution models and their yields are presented showing the impact of three different 12C +12C reaction rates.

An enhanced 12C +12C rate causes core carbon burning to be ignited more promptly and at lower temperature. This reduces the neutrino losses, which increases the core carbon- burning lifetime. An increased carbon-burning rate also increases the upper initial mass limit for which a star exhibits a convective carbon core (rather than a radiative one). Carbon-shell burning is also affected, with fewer convective-shell episodes and convection zones that tend to be larger in mass. Consequently, the chance of an overlap between the ashes of carbon-core burning and the following carbon shell convection zones is increased, which can cause a portion of the ashes of carbon-core burning to be included in the carbon shell. Therefore, during the supernova explosion, the ejecta will be enriched by s-process nuclides synthesized from the carbon-core s-process.

Maxwellian-averaged cross-sections
Kippenhahn diagrams, 15 & 20M
Carbon-core burning lifetimes

The 12C +12C reaction and the impact on nucleosynthesis in massive stars - 2012
In this paper, we explore the impacts of the uncertain C-burning reaction and the relative strengths between the different channels 12C(12C,α)20Ne, 12C(12C,p)23Na, 12C(12C,n)23Mg. A high 12C +12C rate may lead to lower central C-burning temperatures and to 13C(α,n)16O emerging as a more dominant neutron source than 22Ne(α,n)25Mg, increasing significantly the s-process production. This is due to the chain 12C(p,γ)13N followed by 13N(β+)13C, where the photodisintegration reverse channel 13N(γ,p)12C is strongly decreasing with increasing temperature. Here we show the impact of the 12C +12C reaction uncertainties on the s-process and on explosive p-process nucleosynthesis in massive stars.

Maxwellian-averaged cross-sections
Fluxes in and out of 23Na
Fluxes in and out of 22Ne