[Mesa-users] Blue loops

[Jeremy Sakstein]

Thanks Radek,

Does that mean that some Cepheids observed (say 13M) are crossing the
instability strip on their journey to the RGB or do I need to put special
parameters into my I list to delay helium core burning?

Cheers,

Jeremy

On Thu, Apr 4, 2019 at 2:21 AM Radek Smolec <smolec at camk.edu.pl> wrote:

>
> One final question: I can’t  seem to get blue loops that cross the
>> instability strip for say 13M models.
>>
> Above some mass loops disappear in most evolutionary calculations I'm
> aware off. Above 10Ms loops may be difficult to get, independent what
> parameters you are using.
> Check when core helium burning starts in your model. For massive models
> central helium burning starts already on the way to RGB and loops do not
> develop.
> Cheers,
> Radek
>
>
>>
>> Do I need to change the controls in the inlist due to other physical
>> processes kicking in?
>>
>> Cheers,
>>
>> Jeremy
>>
>> On Wed, Apr 3, 2019 at 12:54 PM Jeremy Sakstein <sakstein at sas.upenn.edu>
>> wrote:
>>
>>> Thanks Radek,
>>>
>>> It looks very similar to the inlist I am using so that is good. The only
>>> difference is the mixing length scheme. I think for my purposes as long as
>>> I am consistent this should not matter too much.
>>>
>>> Cheers,
>>>
>>> Jeremy
>>>
>>> On Wed, Apr 3, 2019 at 11:34 AM Radek Smolec <smolec at camk.edu.pl> wrote:
>>>
>>>> Jeremy,
>>>> for 5M_cepheid_blue_loop see the recent public release.
>>>> I attach the relevant inlist for your reference.
>>>>
>>>> You may also take a look at Section 2.4.2 of the instrument paper:
>>>> https://arxiv.org/abs/1903.01426
>>>> Tracks in Figure 13 were computed using this test_suite example.
>>>> Cheers,
>>>> Radek
>>>>
>>>>
>>>> śr., 3 kwi 2019 o 17:25 Jeremy Sakstein <sakstein at sas.upenn.edu>
>>>> napisał(a):
>>>>
>>>>> Thanks Radek,
>>>>>
>>>>> Comments below.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Jeremy
>>>>>
>>>>> On Wed, Apr 3, 2019 at 11:21 AM Radek Smolec <smolec at camk.edu.pl>
>>>>> wrote:
>>>>>
>>>>>> Dear Jeremy,
>>>>>>
>>>>>> śr., 3 kwi 2019 o 16:55 Jeremy Sakstein <sakstein at sas.upenn.edu>
>>>>>> napisał(a):
>>>>>>
>>>>>>> Dear Mesa community,
>>>>>>>
>>>>>>> I've been using MESA to calculate blue loops for Z=0.0006 Cepheids
>>>>>>> in the mass range [image: 5-13 M_\odot] and had a couple of
>>>>>>> questions I was hoping you could answer.
>>>>>>>
>>>>>>> Nominally, I am a theorist so my approach so far has been to use the
>>>>>>> inlist for 7M pre MS to AGB with
>>>>>>>
>>>>>> You may also start with 5M_cepheid_blue_loop in the test_suite.
>>>>>>
>>>>>
>>>>> Thanks. I didn't see this in the test suit (I am using 10398*)*
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> mixing_length_alpha = 1.73
>>>>>>> initial_z = 0.0006
>>>>>>> alpha_semiconvection = 0.1
>>>>>>> use_Ledoux_criterion = .true.
>>>>>>>
>>>>>>> and cary the initial mass over this range.
>>>>>>>
>>>>>>> Initially, I was only using 7-9 [image: M_\odot] but now I need to
>>>>>>> push to a larger range and am getting funny results e.g. the loops cross.
>>>>>>>
>>>>>> What do you mean by "the loops cross"? That single evolutionary track
>>>>>> passes through the same (Teff, L) point? For larger masses this is
>>>>>> expected.
>>>>>>
>>>>>
>>>>> Yes, that is what I mean. Good to know this is normal.
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> I am wondering if what I am doing is sensible given that the physics
>>>>>>> of these objects could be very different depending on mass. In particular,
>>>>>>> I am not sure what people typically use for e.g. the semi-convection
>>>>>>> parameter at higher and lower masses.
>>>>>>>
>>>>>> I'm not sure what is the range of semi-convection parameter
>>>>>> considered in the literature. 0.1 seems raesonable.
>>>>>> Note that the shape and extent of the loops is very sensitive to many
>>>>>> parameters: chemical composition, overshooting from the convective regions,
>>>>>> rotation...
>>>>>> Cheers,
>>>>>> Radek
>>>>>>
>>>>>>
>>>>>>> I'd be grateful for any help you can give.
>>>>>>>
>>>>>>> Cheers,
>>>>>>>
>>>>>>> Jeremy
>>>>>>> _______________________________________________
>>>>>>> mesa-users at lists.mesastar.org
>>>>>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>>>>>
>>>>>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20190405/c02191f2/attachment.html>