mesa-users] mesa eos needs to be extended into the very low T and low density region

Bill Paxton paxton at
Sun May 4 10:39:22 EDT 2008

Hi Falk (and Didier),

> On May 4, 2008, at 7:19 AM, Falk Herwig wrote:
>> Bill, I am forwarding your request to Didier Saumon at Los Alamos.

Thanks Falk -- that's an excellent idea!

Didier, as you may recall, the mesa/eos is a blended combination of  
Frank Timmes' HELM for high T with OPAL and SCVH for lower T.  The  
missing piece is the region that is below OPAL in temperature and  
below SCVH in density.  I'm running models out to the photosphere  
(gray atmosphere, optical depth of 2/3), and with extremely low  
masses (0.02Msun in the example in my original email), and the  
surface of the model is extending into the missing region.  Ideally  
we'd have a continuation of SCVH to much lower densities and/or a  
continuation of OPAL to much lower temperatures.  I think the main  
deviation from ideal gas that comes into play is the H to H2  
transition.  I'm sure there are lots of other difficult things to  
deal with in a full solution, but neutral gas of atoms with H and H2  
in transition would be a wonderful first step.


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