[mesa-users] Angular momentum luminosities

[Richard Townsend]

Hi folks —

I’m attempting to calculate angular momentum luminosities for MESA models — that is, the net amount of angular momentum passing through each cell boundary per second.

Reading Appendix B.6 of the MESA II instrument paper, the luminosity should be the term in the square brackets of eqn. B4. Thus:

L_J = (4 pi r^2 rho)^2 i nu domega/dm

I evaluate this as

L_J = (10**am_log_sig)*(i_rot)*(domega/dm)

where am_log_sig and i_rot are taken from profile files, and the gradient domega/dm is evaluated numerically from omega and m=mass*M_SUN (also from profile files).

Here is a plot of L_J vs m for a ~ 4Msun star about halfway through its main sequence evolution. The star rotated at v = 100 km/s on the ZAMS.

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My question is this: the angular momentum luminosity is *much* smaller than I expect. Given a peak luminosity of ~ 10^5 g cm^2 s^-2, and total initial angular momentum ~ 10^51 g cm^2 s^-1, the timescale for the star to redistribute its angular momentum is longer than the age of the universe.

So, I’m guessing that I’m messing up the L_J calculation. Can anyone spot my error? I attach a copy of the profile, for reference.

Many thanks,

Rich

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