[mesa-users] Problem with evolving pure helium stars

[Philip D. Hall]

Hi Ylva,

It might be helpful to send your inlist. Using the attached inlist with
MESA r7624, I successfully created a 0.5 Msol He star which completed core
He burning and became a white dwarf in about 2000 steps.

&star_job

    create_pre_main_sequence_model = .true.

/ !end of star_job namelist


&controls

    initial_mass = 0.5
    initial_y = 0.9866
    initial_z = 0.0134

/ ! end of controls namelist

Philip D. Hall
Armagh Observatory

On 9 September 2015 at 09:46, Aaron Dotter <aaron.dotter at gmail.com> wrote:

> Hi Ylva,
>
> On the contrary, you have achieved He burning.  (Congrats!)  See that
> lg_L3a is 1.25, central temperature is above 10^8 K, and central He is
> falling.  That it took 50,000 timesteps to reach this point is not very
> efficient, though.
>
> If you say more about what you want to achieve perhaps we can suggest a
> better way.
>
> Aaron
>
>
> On Wednesday, September 9, 2015, Ylva Götberg <y.l.l.gotberg at uva.nl>
> wrote:
>
>> Hi Aaron,
>>
>> Thanks for your quick reply!
>>
>> The 0.5 MSun star looks like this when 50 000 models is reached:
>>
>>
>> That is 7.6 Myrs old, 10^8.0699… K in the centre and a surface gravity of
>> log(g) = 6.06.
>>
>> I see your point with contraction not being sufficient for burning, I
>> should maybe think of another way of initialising these stars..
>>
>> Thanks again!
>> Ylva
>>
>> On 9 Sep 2015, at 10:23, Aaron Dotter <aaron.dotter at gmail.com> wrote:
>>
>> Hi Ylva,
>>
>> You say "when the star should start burning it doesn't succeed".  What
>> are you expecting to happen?  It's not going to do H-burning so the first
>> burning phase will be He burning via triple-alpha.  That should start
>> at roughly 10^8 K but I can well imagine that it is never able to reach
>> such a high temperature via contraction.
>>
>> What is the age of the "star" when the run stops?
>> What is the maximum central temperature achieved?
>> What is the surface gravity at the end of the run?
>>
>> Aaron
>>
>> On Wednesday, September 9, 2015, Ylva Götberg <y.l.l.gotberg at uva.nl>
>> wrote:
>>
>>> Hello everyone,
>>>
>>> I am trying to evolve single stars made of helium and with solar
>>> metallicity (no hydrogen at all). They don’t find a solution after 50 000
>>> models (varcontrol), so I guess I wrote something wrong. In the
>>> inlist_project I have put the following lines to specify it is a helium
>>> star:
>>>
>>>   ! Initial metallicity
>>>     initial_z = 0.0134
>>>
>>>   ! Helium content
>>>     initial_y = 0.9866
>>>
>>> and nothing else. The pre-main sequence goes well, but when the star
>>> should start burning it doesn’t succeed. I have tried masses of 0.5 MSun
>>> and 5.5 MSun.
>>>
>>> Is there anyone who knows what is happening and how I can solve this?
>>>
>>> Cheers,
>>> Ylva (PhD in Amsterdam)
>>>
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>>
>
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