TYCHO: physics sources

Microscopic physics derived from:

Opacity

At temperatures above about 10,000K the opacitiy is that of Rogers and Iglesias 1996 ApJ 464, 943. (See also The OPAL Opacity Code, and The Opacity Project) For lower temperature, the opacity is smoothly interpolated from tables; these opacities are formulated for several different compositions. See Alexander, D. R. & Ferguson, J. W. 1994, ApJ, 437, 879, Low-temperature Rosseland opacities.

TYCHO chooses the appropriate metallicity and interpolates between tables for different hydrogen nucleon fractions at the given metallicity at each timestep.

Both type 1 and type 2 OPAL opacity tables are implemented, and may be chosen at runtime.

Reaction Networks

Nuclear reaction networks: Arnett, D., Supernovae and Nucleosynthesis, 1996, Princeton University Press

The reaction network is user-defined; the present default is a 177 nucleus network which is adequate for the energetics of all stages prior to core-collapse, and for nucleosynthesis for all stages except for s-process, r-process and p-process which involve rare nuclei. The light nuclei D, He3, Li, Be, and B are treated with a low-temperature network, which merges into the larger network as temperature rises.

Thermonuclear reaction rates

Nuclear reaction rates: originally from Thielemann, Truran, and Arnould,, with updates by Arnett. See also Basel astrophysics.

In progress: updating, using NACRE, Rauscher and Thielemann (nonsmoker), and for p-induced reactions Iliadis, et al.

John Bahcall's exportenergy.f subroutine has been used to construct an option for models of the sun. Weak screening is interpolated to strong screening; the standard results of Graboske and Salpeter are used as in exportenergy.f.

Equation of State

Equation of state: Helmholtz Free energy formulation (adapted for all T, and density rho < 1.0e12 g/cc), See Timmes and Arnett 1999 ApJS 125, 277, and Timmes and Swesty 2000 ApJS 126, 501 . For coulomb effects (T < 1.0e8 K), Rogers, Swenson, Iglesias 1996 ApJ 456, 902. Either Helmholtz or OPAL eos may be chosen at runtime, and a merged option is in progress.

Diffusion and Radiative Levitation

Settling by gravitationally driven diffusion is based upon the Thoul subroutine from John Bahcall's website. Radiative levitation is not yet implemented.

Neutrinos

Neutrino cooling is based on Itoh, et al., (1996) ApJS 102, 411, except for plasma neutrinos which are based on Kantor and Gusakov, (2007) MNRAS 381, 1702. The subroutine sneut96.f is due to Jordi L. Gutierrez (2007).

Electron Conduction

The original treatment of electron conduction is based upon fits to tables of Hubbard and Lampke. Use of newer results by Itoh is planned.

Return to main TYCHO page.

E-mail:darnett@as.arizona.edu

TYCHO is not public domain software, but is freely available for non-commercial purposes. Absolutely no guarantee is given; use at your own risk...