[mesa-users] The Cepheid phase

[Bill Paxton]

Hi Earl,

While Radek is off on holiday for the month of August, you might want to play with these.  I believe I'm using tricks that Radek taught me about getting blue loops in mesa -- but don't count on it.  Here's an example (9Msun; Z=0.02) showing that we can get multiple loops ending in a return to the L-Teff at the base of the RGB.  Very weird.
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i did this run on my current development version, but i expect it will work with minor revisions in the current mesa (8845)
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Good luck,
Bill




On Jul 30, 2016, at 9:11 AM, Earl Bellinger wrote:

> Excellent, thank you very much! Inlists would be very helpful.
> 
> Best regards,
> Earl Bellinger
> Stellar Ages & Galactic Evolution Group
> Max-Planck-Institut f?r Sonnensystemforschung
> 
> 
> On Fri, Jul 29, 2016 at 9:07 PM, Radek Smolec <smolec at camk.edu.pl> wrote:
>> 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 f?r Sonnensystemforschung
>>> 
>>> 
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>> 
>> 
> 
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