[mesa-users] Learning stellar evolution and asteroseismology using MESA

[Cyrus Zalian]

Thanks for your answers Josiah and Francis.

Sorry for the time it took me to answer but I was going through the 2013
summer school material Francis advised me. It was as interesting as I
expected. As I said earlier, working on a project with MESA is an excellent
tool for learning about astrophysics.

Considering my earlier questions, I understood that in most case a preMS
were built (thus the few steps/max age in the inlist file to obtain a fully
convective star as Josiah said), and in a second step were used for various
studies. I stil don't understand why this step is necessary, and why we
don't "merge" the two inlist (the preMS  and the following one) but this is
just a detail (I imagine it has something to do with the added options in
the second step).

Now, if I sum it up, I have two problems :

1) Find a stopping condition or a selecting condition for RR Lyrae. I'll
have to jump in books and papers to find (and as I'm one a tight schedule,
any help would be welcomed)

2) Understand the output from GYRE : I have to admit I'm a bit lost with
asteroseismology and the GYRE output. What I've been doing up to know is
analyzing the light curve of a star and perform a Fourier decomposition
looking for the main frequency and possible overtone. But I have no idea
how I can find that with Gyre, and hence how to do a Petersen diagram, as
it outputs a lot of frequencies. I might show my lack of knowledge, but
first I should only look for l=0 (as I look for radial modes only).
Then...well I don't know...

I've read Richard Townsend summer school material, but still doesn't help
me unfortunately...All in all, I'm lost because, once again, I have a
consequent lack of knowledge, but morevover I don't know were too find it...

Anyway, once again thanks for your help Josiah and Francis.



2015-02-24 17:54 GMT+01:00 Josiah Schwab <jwschwab at berkeley.edu>:

> Hi Cyrus,
>
> > 1) the first step, from what I understand, is to build a pre main
> sequence.
> > I just copy the star/work directory in a personal one, and in the
> > corresponding inlist file, we just need to indicate the initial mass and
> Z
> > (0.71 and 0.0001 respectively for my first case). If nothing is wrong up
> to
> > now, my only question would be : what should be stopping condition ? The
> > tutorial inlist file indicates Lnuc / L > 0.99 and the astero example
> > inlist file indicates a max model number of 30 (by the way, where the
> first
> > one comes "theoretically" ; and for the second one why 30 ?).
>
> Physically, a star reaches the main sequence when L ~ L_nuc.  So the
> stopping condition Lnuc / L > 0.99 means that MESA stops when the star
> has reached the zero age main sequence (ZAMS).
>
> In the second case, the inlist begins with a pre-main sequence model and
> evolves it for a small number of steps.  Why exactly 30 was chosen, I
> don't know, but that is significantly less than the number of steps it
> will take to reach the ZAMS.  So this model is still a pre-main sequence
> (PMS) model, fully convective with a luminosity greater than it will
> have on the main sequence.
>
> > 2) Now that I have a pre_ms star can there be one inlist file describing
> > the evolution of the star from main sequence to a RR Lyrae type star ? If
> > yes, what should be the stopping condition (if I'm not wrong there's no
> > predefined stopping condition for that specific purpose...then how would
> I
> > recognize that it has reach a RR Lyrae type model) ? If I'm asking this
> > question is that the astero_example inlist file contains not two but
> three
> > inlist, on fro pre MS and two others.
>
> I don't know much about RR Lyraes, but MESA allows you to check any
> conditions you want using run_star_extras.f.  See e.g.,
>
> http://mesa.sourceforge.net/run_star_extras.html#toc-2
>
> So first you should write down what physical conditions you want to use
> as the stopping trigger.  Then work on translating that into some
> fortran code.  You can likely get help with this second step on-list.
>
> In terms of what you should include in your PMS -> RR Lyrae inlists, you
> may want to look at some test suite problems or talk with someone
> working on this or related topics.
>
> Hope that helps,
> Josiah
>
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