[mesa-users] Problem with evolving pure helium stars

[Aaron Dotter]

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
> <javascript:_e(%7B%7D,'cvml','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
> <javascript:_e(%7B%7D,'cvml','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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