[mesa-users] Problem with evolving pure helium stars

[Ylva Götberg]

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 <mailto: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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