Microphysics Modules
These modules calculate various functions based on local properties of the stellar matter such as temperature, density, and composition. There are modules for equation of state, opacity, nuclear reactions, and neutrino losses.
MESA/EOS
MESA/KAP
MESA/RATES
MESA/NET
MESA/NEU
MESA/IONIZATION
MESA/CONST
MESA/CHEM
MESA/EOS
The MESA/EOS module provides a smooth blending of three widely used equations of state: HELM, OPAL, and SCVH.
References
F.X. Timmes and F.D. Swesty, “The Accuracy, Consistency, and Speed of an Electron-Positron Equation of State Based on Table Interpolation of the Helmholtz Free Energy”, Astro. J. Supplement Series, 126, 501-516 (2000). pdf
F. J. Rogers and A. Nayfonov, “Updated and Expanded Opal Equation-Of-State Tables: Implications for Helioseismology”, Astrophys. J., 576, 1064-1074 (2002). pdf
D. Saumon, G. Chabrier, and H. M. Van Horn, “An Equation of State for Low-Mass Stars and Giant Planets”, Astrophysical Journal Supplement Series, 99:713-741 (1995) pdf
MESA/KAP
In addition to OPAL Type I and Type II tables, MESA/KAP includes updated Ferguson et al. low temperature opacities and updated Potekhin et al. conductive opacities.
References
C. A. Iglesias and F. J. Rogers, Astrophys. J. 464, 943 (1996). pdf
C. A. Iglesias and F. J. Rogers,”Radiative Opacities for Carbon- and Oxygen-Rich Mixtures,” Astrophys. J. 412, 752 (1993). pdf
Ferguson et al. “Low Temperature Opacities”, ApJ, 623, 585-596 (2005). pdf
S. Cassisi, A. Y. Potekhin, A. Pietrinferni, M. Catelan, M. Salaris (2007). Updated electron-conduction opacities: the impact on low-mass stellar models. Astrophys. J., 661, 1094 [astro-ph/0703011].
MESA/RATES
The MESA/RATES module supplies nuclear reaction rates as functions of temperature. The available rates come from a variety of sources, including NACRE (Angulo et al., 1999) and Caughlin & Fowler (1988).
References
Caughlin, G. R. & Fowler, W. A. 1988, Atom. Data and Nuc. Data Tables, 40, 283.
C. Angulo et al., Nucl. Phys. A656 (1999) 3-187.
MESA/NET
The MESA/NET module implements the nuclear reaction networks using reaction rates from MESA/RATES. It is based on Frank Timmes’ code and includes a basic net for standard stellar evolution and a set of extensions that can be used in any combination.
the ‘basic net’
This is for standard hydrogen, helium, and carbon/oxygen burning. It includes 3 PP chains, 4 CNO cycles, triple alpha, alpha chains up to mg24, and carbon/oxygen burning. The isotopes explicitly followed are h1, he4, c12, n14, o16, ne20, and mg24. The n14 alpha chain is “short circuited” into the c12 chain by the pseudo-reaction n14 + he4 -> 0.5 * (o16 + ne20).
The triple-alpha reaction in the pyconuclear regime is supported according to the analytic expressions in Fushiki and Lamb, 1987.
the ‘Alpha chain’ extension
This adds an alpha chain linking mg24, si28, s32, ar36, ca40, ti44, fe52, and ni56.
the ‘full PP’ extension
This fills out the set of isotopes involved in the PP chains by adding h2, he3, li7, and be7.
the ‘full CNO’ extension
This adds hot cno reactions and some early rp process reactions. The added isotopes are c13, n13, n15, o14, o15, f17, f18, ne18, and ne19. In addition, we include the initial part of the rp process by adding mg22 and the reactions leading to it. Any significant build up of mg22 indicates the need for a more complete rp network.
There are currently two options for screening: the “classic” Graboske method, and an extension of that based on Frank Timmes’ routine.
The Graboske implementation follows the 1973 papers (DeWitt, Graboske, Cooper; Graboske, DeWitt, Grossman, Cooper). The Timmes scheme extends the Graboske method using results from Alastuey and Jancovici (1978), along with plasma parameters from Itoh et al (1979) for strong screening.
References
F.X. Timmes, “Integration of Nuclear Reaction Networks for Stellar Hydrodynamics”, The Astrophysical Journal Supplement Series, 124, 241-263 (1999). pdf
DeWitt, Graboske, Cooper, “Screening Factors for Nuclear Reactions. I. General Theory”, ApJ, 181:439-456, 1973.
Graboske, DeWitt, Grossman, Cooper, “Screening Factors for Nuclear Reactions. II. Intermediate Screening and Astrophysical Applications”, ApJ, 181:457-474, 1973.
Alastuey and Jancovici, ApJ, 226, 1034, 1978.
Itoh et al, ApJ, 234, 1079 1979.
MESA/NEU
The MESA/NEU module is for calculating energy loss rates for neutrinos from sources other than nuclear burning. It is based on Frank Timmes implementation of the analytic fitting formulas given in the following reference.
Reference
Itoh, N., Hayashi, H., Nishikawa, A., & Kohyama, Y. “Neutino Energy Loss in Stellar Interiors. VII. Pair, Photo-, Plasma, Bremstrahlung, and Recombination Neutrino Processes”, ApJS, 102, 411-424 (1996). pdf
MESA/IONIZATION
The MESA/IONIZATION module provides a routine to estimate typical ionic charge as a function of local temperature, density, and free electrons per nucleon.
Reference
C. Paquette, C. Pelletier, G. Fontaine, G. Michaud, “Diffusion in White Dwarfs: New Results and Comparative Study”, ApJ Supp. Series, 61:197-217, 1986.
MESA/CHEM
The MESA/CHEM module provides a common source of information about the isotopes used by the rest of the system.
MESA/CONST
The MESA/CONST module provides a definitions for many widely used physical constants.
website design by
Andreas Viklund