[Mesa-users] YNT: Stars older than universe

[Gökhan Yücel]

Hello everyone,

Fahri,

I had tried with different Z values and it changes the age drastically. I attached the model files with different Z values. But I think there is a different situation in this matter.
As you said in your previous mail that I didn't use rotation, at least used 0. As in parameters in the file of "inlist_project", I thought rotation and its value added automatically. Obviously I was wrong. What's the best way to include rotation for a specific value? For example, for value of vsini = 50 km/s, which parameters should I add the inlist? Or should I add rotation in different way?

Warrick,

I have made some models with different Z values and it changes its age drastically. But there is no rotation in process of making the models.

For Z=0.005, the age is 10.836 M
For Z=0.010, the age is 3.348 B
For Z=0.015, the age is 9.335 B
For Z=0.020, the age is 16.14 B
For Z=0.025, the age is 21.428 B

May be as Rob said I should use binary mode.

Thanks,
Gökhan
________________________________________
Kimden: Fahri Aliçavuş [fahrilcvs at gmail.com]
Gönderildi: 14 Aralık 2020 Pazartesi 16:34
Kime: Gökhan Yücel
Bilgi: mesa-users at lists.mesastar.org
Konu: Re: [Mesa-users] Stars older than universe

Hello Gökhan,
I think Rob is right, you should use the Binary module anyway. and you have to consider effects such as rotation, magnetic braking. You should also consider orbital evolution because in the last case they have a period of about 1 day and the components affect each other.

For the situation, here are some  possibilities:

-Stars may be a pre-main sequence.

-The system may have started its evolution with a high eccentricity, in which case mass transfer may occur even if it is detached (in some phases).

- You can try different Z's. you may also consider rotation (you used zero)

-You should also consider that the radius error in the article is given around 13%.

However, if you compare your results with Mist (http://waps.cfa.harvard.edu/MIST/interp_tracks.html), the age of the star should be around 2-3 Gyr (if it is a main-sequence star) for the radius of the star. So, you probably make a mistake somewhere while producing models.

Cheers,
Fahri

Gökhan Yücel <gokhanyucel at akdeniz.edu.tr<mailto:gokhanyucel at akdeniz.edu.tr>>, 14 Ara 2020 Pzt, 10:50 tarihinde şunu yazdı:
Hello everyone,

I have been doing evolution of binary stars that their stellar parameters are well known until mass transfer starts. To do that, I simple evolve single stars until they reach to their current radii and save their models. After that I use binary mode to evolve them. I have been successful to do that for a while but I have encountered some sort of situations while doing a single star evolution. Some very low mass stars, M spectral type specifically, has an age more than universe itself according to models. I believe something is wrong in here. I have checked the parameters and how they had been calculated and there is nothing in this area. This has happened some other stars, all of them are very late types, too.

M = 0.489 Msun, R = 0.453 Rsun

I attached the files. I am using mesa version of "r12115" and SDK version of "20190830".

What am I doing wrong?

Sincerely,
Gökhan
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