[mesa-users] logQ_limit and the ZAHB

Aaron Dotter aaron.dotter at gmail.com
Thu Aug 11 08:59:40 EDT 2016


Hi Jeremy,

>From controls.defaults,

logQ = logRho - 2*logT + 12

is a variable used in the EOS density-temperature tabulation.  Those EOS
tables are quite generous in the parameter space they cover, so I suggest
that you verify that your mods are actually small, and have only a modest
influence on stellar evolution.  The maximum logQ in the eosDT tables is
5.69 so you can increase logQ_limit up that value.

Aaron

On Thu, Aug 11, 2016 at 4:35 AM, Jeremy Sakstein <jeremy.sakstein at port.ac.uk
> wrote:

> Hi Guys,
>
> I'm trying to evolve stars of Z = 0.0001 from the pre-MS to the zahb,
> which I do following some insists Bill sent me where I evolve to the ZAMS
> then to the helium flash then to the ZAHB.
>
> This works perfectly when I don't use any of my other mods but as soon as
> I turn on even a small modification (my mods change the theory of gravity)
> then either the code does not converge and the star stays near the helium
> flash with an increasingly small time step or I get the error message:
>
> stop because hit EOS limits -- max_logQ > logQ_limit
>
> I can see how this is set in controls_default but what does this really
> mean? I am not sure what logQ is. What is so different from the standard
> case that the code needs to stop for this reason?
>
> Is there anything to stop me raising the limit manually or is this
> sensible thing to do
>
> I should say I am using version 7623.
>
> Cheers,
>
> Jeremy
>
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