[mesa-users] Creating a gamma Dor model

[Francis Timmes]

generally, the pressure and thermal energy from the iben eos 
is within 0.1% of other independent eos routines and the 
derivatives of those quantities are within 1%. the largest
deficiency of the iben eos is that it does not include positrons,
a very reasonable approximation for the main topics that icko pioneered.

if one would like to basis for the statements above:

http://adsabs.harvard.edu/abs/1999ApJS..125..277T

and if one is so inclined, the iben eos can be downloaded here:

http://cococubed.asu.edu/code_pages/eos.shtml

fxt





> On Jul 13, 2016, at 5:12 PM, Ehsan Moravveji <e.moravveji at gmail.com> wrote:
> 
> Hi Rich,
> 
> Naively, I just took a very quick peek at the Sect. 2 in Warner et al. (2003)  and noticed that there is a significant version difference between the EOS they use (Iben 1976), compared to that of MESA (updated OPAL 2005). Since nabla_ad is among the return columns of the EOS, “perhaps”, the difference you see in your boundary locations stems from different EOS values for nabla_ad through the two EOS versions. 
> If this is so, I do not have an immediate idea how to “downgrade” to the old EOS, and reproduce Warner's models; else, let’s hope that the more recent MESA EOS gives is more accurate in providing nabla_ad values. 
> 
> B.t.w. the clocks have ticked since the 70s, and our understanding of stellar EOS has advanced. Thus, your model “might be” a more accurate representation of gamma Dor stars: Your instability strips will tell ;-)
> 
> The good thing is that your composition (Z=0.02, Y=0.28) and mixture (GN93) is identical to theirs. 
> 
> Best regards,
> Ehsan.
> 
>> On 13 Jul 2016, at 20:03, RICHARD H D TOWNSEND <townsend at astro.wisc.edu> wrote:
>> 
>> Hi folks —
>> 
>> I’m interested in creating a models for gamma Dor stars, in which gravity modes are unstable due to convective flux blocking. I’ll be using GYRE to do the stability calculations; I appreciate that the convection-pulsation interaction probably needs a more-sophisticated approach than GYRE’s current method (convective freezing), but for now GYRE should suffice.
>> 
>> My first step is attempting to reproduce some of the gamma Dor models presented in Warner, Kaye & Guzik (2003, ApJ 593, 1049). However, try as I might, I seem to end up with models that don’t have the (relatively) thick outer convection zone reported by Warner et al.
>> 
>> As a specific example, I attach a MESA inlist which aims to reproduce the M=1.55 Msun model reported in Table 1 of Warner et al. Running this inlist with MESA 8118 results in a final model with the following properties:
>> 
>> Teff = 6927 K
>> L/Lsun = 6.82
>> Age = 1.049 Gyr
>> 
>> This model is somewhat cooler than the model reported in Warner et al (their Teff = 6965K), but the difference is small. The luminosity matches exactly, and the age is close (their age = 1.076 Gyr). So, it looks like I’m in the right ballpark.
>> 
>> However, when I look at the internal structure of the model, I’m struck by the fact that the inner edge of the envelope convection zone is at T ~ 63 kK (logT ~ 4.75), rather than the ~ 240 kK (logT ~ 5.4) reported by Warner et al. Here’s a plot of the radiative vs total flux, as a function of temperature, which demonstrates this:
>> 
>> <figure_1.png>
>> 
>> Indeed, I find that to get the convection zone(s) to extend to deeper layers, I have to allow the star to be significantly cooler and more evolved.
>> 
>> Since I’m not all too familiar with gamma Dor stars, I’m likely making a stupid mistake in my inlist file. Can anyone suggest what might be the problem?
>> 
>> Many thanks,
>> 
>> Rich
>> 
>> <inlist><profile_columns.list>
>> 
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