[mesa-users] irradiation in binary_donor_only

[Pablo Marchant]

thomas, please keep mesa-users on the loop while replying. You just wrote
me that lg_Teff seems to be the cause for your timestep limit. When you
want to see timestep controls, check out star/defaults/controls.defaults,
and go to the section on "timestep controls". At the beggining there is a
description for all the limits, you will see this one there:

!          'lgTeff'               delta_lgTeff_limit

First column is the string from the terminal output, second is the name of
the control associated to it. So look for the delta_lgTeff_limit variable,
the default value is

delta_lgTeff_limit = 0.01

so timestep will be reduced if your star experiences jumps in Teff larger
than this magnitude. If you started from the "binary_donor_only" then I'm
guessing you are computing mass transfer rates explicitly, this can cause
large jumps in the mass transfer rate, which will cause large changes in
the amount of radiation, which will make Teff jump around, causing this
limit to kick in. This is just a guess, but from it I can recommend you to
check two things:

1) Are you using the implicit or explicit scheme for mass transfer? You can
activate the implicit scheme with "max_tries_to_achieve = 50" in the
binary_controls section of inlist_project.
2) You can try incresing delta_lgTeff_limit, but I think the default limit
should be quite lenient for most situations so you should certainly try
number 1) first.

Cheers!

On Thu, Mar 5, 2015 at 9:42 AM, Pablo Marchant <pamarca at gmail.com> wrote:

> Hi Thomas. Timesteps can be reduced due to convergence problems, or just
> because the default timestep controls are too restrictive. Do you have an
> idea what's the source of your timestep reduction? The terminal output
> shows the source of timestep limits (check the last column of output,
> second row. It often says varcontrol).
>
> Cheers!
>
> On Tue, Mar 3, 2015 at 3:58 PM, thomas c.d. (cdt1g11) <cdt1g11 at soton.ac.uk
> > wrote:
>
>>  Hi! im currently investigating the effects of irradiation on the
>> evolution of binary systems, specifically starting with an accretor mass of
>> 1.4M_sun and donor mass of 1.0_M_sun. using an initial period of 2.0 days
>> one would expect angular momentum losses, roche lobe overflow and
>> accretion.
>>
>>  I’m looking into the effects of x-rays, from this accretion, on the
>> donor star. To do this i am using the binary_donor_only module in the
>> binary suite. when setting in the project inlist
>> accretion_powered_irradiation = .true. we see some effects of
>> irradiation. however when we then use different values of
>> col_depth_for_eps_extra we encounter a problem for any value <1.
>> specifically, as mass loss begins the time step reduces to a size so small
>> it’s impractical for running the code; 1 test saw 750,000 models calculated
>> without progressing a single year in age.
>>
>>  Does anyone have any wisdom for solving this issue? would be greatly
>> appreciated!
>> thanks!
>>
>>  Callum Thomas
>>
>>
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>
>
> --
> Pablo Marchant Campos
> M.Sc on Astrophysics, Universidad Católica de Chile
> PhD student, Argelander-Institut für Astronomie
>



-- 
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD student, Argelander-Institut für Astronomie
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