[mesa-users] resending - Questions about physical model and numerical implementation of binary star evolution

[Dean Townsley]

Hello,

 From the plots in your first email, this looks like the expected 
behavior for a secondary star losing matter via mass transfer to a 
primary.  When the donor loses enough mass to get down from 0.8 to about 
0.2 Msun, it becomes fully convective, at which point the abundances are 
constant since the star is fully mixed.  Also since the star is steadily 
becoming less massive, its luminosity and temperature are both steadily 
decreasing.

Are you concerned that it shouldn't be in contact yet?  What is 
happening to the primary?  I would have expected the integration to stop 
when the primary became a giant.

Maybe that helps.  I didn't have the chance to try your inlists.

Dean

On 12/10/2014 05:28 PM, 이현택 wrote:
> Dear MESA users,
>
> I have some questions regarding numerical model of binary star simulation.
>
>
> 1)
> During the low mass binary simulation,(1.0 solar mass and 0.8 solar 
> mass with orbital period of 2 days)
> for the primary star (1 solar mass) it seems that there is no problem. 
> But for secondary star, at some point (around 5 Gyrs) all the 
> abundances becomes constant.
>
> 2)
> Along with the abundance issue, the HR diagram shows only the 
> decreasing tendency of luminosity and surface temperature.
> (i.e. the luminosity and surface temperature only decreases)
>
>
> Please refer to the attached inlist files and png files which shows 
> the issues.
>
>
> What can possibly be the physical meaning of this situation?
> I wonder whether star can interchange their mass by stellar wind 
> before filling Roche lobe.
> And I'd like to know how mesa numerically distinguishes the Roche lobe 
> and the star.
>
> What is the computational implementation of Roche lobe?
>
>
> Thanks in advance.
>
> Sincerely yours, HYUN TAEK-
>
>
>
>
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