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Input Physics

Here we describe the physics associated with the input parameters used in MESA. For a more in-depth review of these parameters please see Paper I, Paper II, or more recently Paper III.


Control Parameters

Nuclear Reaction Network
A net is defined by a set of isotopes and a set of reactions.

Descriptions of some of the nuclear reaction networks provided by the README with mesa/data/net_data/nets/.

for "no frills" hydrogen and helium burning
basic -- h1, he3, he4, c12, n14, o16, ne20, mg24
assumes T is low enough so can ignore advanced burning and hot cno issues.

the following nets provide more complete coverage for hydrogen and helium burning
hot_cno -- basic + c13, n13, n15, o15, o17, o18, f17, f18
for high temperatures where cno becomes beta limited.

cno_extras -- hot_cno + o14, f19, ne18, ne19, mg22
for high temperatures where start to breakout of hot cno.
pp_and_cno_extras -- pp_extras + cno_extras


Mixing

Mixing Length Alpha
l = α Hp ,
where l is the mixing length, α is a free parameter, and Hp is the pressure scale height.

Mixing Length Theory Implementation
- none - Gives radiative values with no mixing.
- Cox - MLT as developed in Cox & Giuli 1968, Chapter 14.
- ML1 - Bohm-Vitense 1958.
- ML2 - Bohm and Cassinelli 1971.
- Mihalas - Mihalas 1978, Kurucz 1979.
- Henyey - Henyey, Vardya, and Bodenheimer 1965.

Convective Overshoot
The overshooting diffusion coefficient DOV is given by
DOV = Dconv,0 exp(-2z/fOVλP,0),
where Dconv,0 is the convective diffusion coefficient measured a distance fOV,0 inside the convective zone, z is the radial distance and λP,0 is the local pressure scale height. Overshooting then extends beyond the edge of the convective zone a distance fOV. Both fOV,0 and fOV are assumed to be given as fractions of the local pressure scale height.

Winds

RGB/AGB Wind Eta
Mass loss efficiency, varies with wind scheme.

Wind Scheme
- Reimers - D. Reimers, Baschek, Kegel, Traving (eds), Springer, Berlin, 1975, p. 229.
- Blocker - T. Blocker A&A 297, 727-738 (1995).
- Kudritzki - Kudritzki et al, Astron. Astrophys. 219, 205-218 (1989).
- Nieuwenhuijzen - Nieuwenhuijzen, H.; de Jager, C. 1990, A&A, 231, 134.
- Vink - Vink, J.S., de Koter, A., & Lamers, H.J.G.L.M., 2001, A&A, 369, 574.
- Grafener - Grafener, G. & Hamann, W.-R. 2008, A&A 482, 945.
- Dutch - Glebbeek, E., et al, A&A 497, 255-264 (2009).

Rotation

Initial Rotation
Rotational value is set at the zero-age main sequence as a fraciton of the critical angular velocity given by
Ω2crit = (1-L/Ledd)GM/R3 ,
where L is the luminosity, Ledd the Eddington luminosity, G the universal gravitational constant, M the stellar mass, and R the stellar radius.