[mesa-users] Specific entropy odd increase in fully convective star

[Ireland, Lewis]

Hi all,

I am modelling a 0.3 solar mass star using the (condensed) following:

&star_job

  ! begin with a pre-main sequence model
    create_pre_main_sequence_model = .true.

/ !end of star_job namelist

&controls

  ! starting specifications
    initial_mass = 0.3d0 ! in Msun units

mixing_length_alpha = 2.0d0

  ! stop when the star nears ZAMS (Lnuc/L > 0.99)
    Lnuc_div_L_zams_limit = 0.99d0
    stop_near_zams = .true.

  ! stop when the center mass fraction of h1 drops below this limit
    xa_central_lower_limit_species(1) = 'h1'
    xa_central_lower_limit(1) = 1d-3

/ ! end of controls name list

For the fully convective case, I expect the entropy to be roughly constant throughout up until the photosphere, but I get an artefact of ds/dr > 0 after about half way through the stellar interior out to the surface (please view attached image - the constant entropy profile (red) is from a formulation that calculates what I should be getting). What is causing this increase in specific entropy at this point? I expect there to be some increase near the photosphere when radiative transfer takes over from convection, but why is it starting to increase so early in the radial profile? Is there another test case I can use to model this kind of star?

Kind regards,

Lewis

[cid:73EEBE75-8E2D-468B-86C9-0B6817F24FCD at ex.ac.uk]
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