[mesa-users] The Cepheid phase

[Jakub Ostrowski]

Hi,

This loop is really weird. I’ve studied blue loops pretty extensively and I can’t recall seeing anything like it. You can take a look at my paper (2015, MNRAS 447, 2378). We tried to determine whether pulsating B-type supergiants can be on blue loops or not. The considered masses are higher (M >= 13 Ms) but our loops behave better. I intend to publish a paper solely focused on the blue-loop problem in massive stars but that’s that's not going to happen until the end of the year. Anyway, the problem is extremely complicated so even the easiest questions might be difficult to answer.

Jakub


> On 30 Jul 2016, at 20:18, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
> 
> 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.
> <H_R.pdf>
> 
> i did this run on my current development version, but i expect it will work with minor revisions in the current mesa (8845)
> <inlist_to_instability_strip><run_star_extras.f>
> 
> 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 für 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 für Sonnensystemforschung
>>>> 
>>>> 
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>>> 
>> 
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