[Mesa-users] YNT: Stars older than universe

[Warrick Ball]

Hi Gökhan,

What's the uncertainty on the radius to which you are evolving these stars?  How much does the age change if you increase or decrease the target radius by one uncertainty?

Also, what's the composition of your target star, and how does that compare to the composition of your model?

Cheers,
Warrick



____________

Warrick Ball
Postdoc, School of Physics and Astronomy
University of Birmingham, Edgbaston, Birmingham B15 2TT
W.H.Ball at bham.ac.uk
+44 (0)121 414 4552


On Mon, 14 Dec 2020, gokhanyucel at akdeniz.edu.tr wrote:

> Hi Rob,
>
> Thanks for quick return.
>
> These systems are detached binaries. Thus, there is no expectation that they will lose mass via mass transfer. That's the reason that I evolve components of these binaries with a single star evolution to reach to their current radii. Once this process is finished, when stars reach their current radii, I use binary mode with two calculated models to evolve the system as a whole.
>
> The age of star should be 14.9 billion years to reach its current radius as you can see from attached model files which is 2MASSJ165002074-2.mod.
>
> Gökhan
>
> ________________________________________
> Kimden: Rob Farmer [r.j.farmer at uva.nl]
> Gönderildi: 14 Aralık 2020 Pazartesi 12:14
> Kime: Gökhan Yücel
> Bilgi: mesa-users at lists.mesastar.org
> Konu: Re: [Mesa-users] Stars older than universe
>
> Hi,
> What's the lifetime of a 0.489msun star? I don't know but it's longer than the age of the Universe, so it does not surprise me that it will keep evolving until then.
>
> You are starting with a 0.489msun star, I assume you choose that as the current mass of 2MASSJ165002074 is expected to be that?  If so, have you considered that your star might have had a higher initial mass and then lost mass to its companion in the binary? So if you started with a higher initial mass star then it would evolve faster.
>
> I would suggest trying to evolve both stars in a binary from the beginning and try running many different initial masses to find one that ends up with the correct mass for 2MASSJ165002074.
>
> Rob
>
>
>
> On Mon, 14 Dec 2020 at 08:49, Gökhan Yücel <gokhanyucel at akdeniz.edu.tr<mailto:gokhanyucel at akdeniz.edu.tr>> wrote:
> 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
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>