Effects of 12C +12C


Astronomy research
  Software Infrastructure:
     My codes
  White dwarf supernova:
     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
     Pre-SN variations
     MC white dwarfs
     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
     MC reaction rates
  Verification Problems:
     Validating an astro code
Software instruments
Bicycle adventures

AAS Journals
2017 MESA Summer School
Teaching materials
Education and Public Outreach
2016 NSF SI2 PI Workshop

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