[mesa-users] The Cepheid phase

[Radek Smolec]

Hi Earl,

The statement in Dziembowski's paper was about helium burning loop and
relatively low mass Cepheids; Fig 14 in the third instrument paper shows
the first crossing only.

The loop is, and was tricky. In many published evolutionary tracks the
presence or extent of the loop do not vary smoothly with mass or Z. It is
difficult to get the loop for near solar metallicities and low masses,
3-5Ms. For lower metallicities and higher masses loops are quite easy to
get. Adding some overshooting from the envelope convection zone helps.

Note that we still have the Cepheid mass discrepancy problem, although it
is significantly reduced, to 10-15%. We know that pulsation theory is right
(Pietrzynski et al., 2010, Nature; other papers with determination of
Cepheid's masses in eclipsing binaries), the evolution calculations need
improvement. The recent papers point that rotation might be a solution.

To summarize, Cepheids can be investigated with MESA, and there are still
some problems to be solved (and lots of parameters to play with :-)

I'm now on holidays; at the end of August I can send you the inlists I used
for Cepheid calculations (but these are old; for MESA 4xxx, I think).
Kind regards,
Radek


2016-07-29 16:40 GMT+02:00 Earl Bellinger <bellinger at mps.mpg.de>:

> Hello everybody,
>
> In Dziembowski's 2012 paper [1] the claim is made that:
>
> > "BaSTI (Pietrinferni et al. 2006) models at M = 4 and 5 do not reach
> > the instability strip [in the helium burning phase] but the maximum
> > values of L in this evolutionary phase are in a good agreement with
> > the relation given by Eq. (2). Similar conclusion was reached by
> > Smolec (private communication), who used public domain code MESA
> > (Paxton et al. 2011). Apparently, new evolutionary codes do not
> > describe well the Cepheid phase."
>
> Can anyone corroborate/evaluate this claim for me please? That is: is
> MESA suitable for investigating Cepheid stars? If not, why not?
>
> For example, can a theoretical Cepheid Period-Luminosity relation be
> derived using MESA plus a pulsation code (ADIPLS/GYRE/etc)?
>
> Thanks for any insights.
>
> [1] http://acta.astrouw.edu.pl/Vol62/n4/pdf/pap_62_4_1.pdf
>
> Best regards,
> Earl Bellinger
> Stellar Ages & Galactic Evolution Group
> Max-Planck-Institut für Sonnensystemforschung
>
>
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