[mesa-users] issue with OP AGSS09

[Bill Paxton]

Hi Craig,

Thanks for the pointer.   Before we get to that, we need to wait for Radek & Jakub to check the mesa opacity tables to see if there is a problem in them.  

Bill




On Oct 11, 2013, at 11:47 AM, Craig Wheeler wrote:

> http://adsabs.harvard.edu/abs/2012A%26A...542A...1L
> 
> Might be relevant.
> 
> Craig
> 
> On 10/11/13 1:22 PM, Bill Paxton wrote:
>> Hi Jakub,
>> 
>> Lovely!  The jumps in core He abundance from 1% to 3% suggest instabilities during the "death" of the core He burning convection zone.  Please check that -- make plots of size of core convection zone during this time and share them with us.  I expect that the convection dies out when core He drops to 1%, but then the core temp rises and you get a burst of convection from that.  The convection briefly reaches up into He rich material and raises the center abundance up to 3% and that lets the core temperature drop.  Then the cycle repeats until the convective bursts can no longer bring down more He.
>> 
>> Since the convection will be sensitive to opacities, the change from GS98 to A09 might be enough to trigger this.   And of course overshooting during He burning can go unstable as you well know.  You have overshooting above he burning turned on:
>>       overshoot_f_above_burn_he = 0.010
>> so that might also be contributing to this.   What happens to this when you run without overshooting?  I expect that will cause you grief in other things, but specifically what effect does it have on these instabilities in core he burning?
>> 
>> My guess is that the A09 tables are fine.  They are just pushing you over the cliff with an overshooting related instability during the final stage of core He burning.    But I'm suspicious of the use of overshooting during core He burning anyway -- it has been very unstable when I've tried it.   But let's see -- maybe it has nothing to do with what you are getting here.
>> 
>> Another question -- you are dealing with opacities in the C/O ashes of He burning, but you are not using Type2 opacities.  Why not?  Have you experimented and found that there was no difference?  That would be a surprise.
>> 
>> -Bill
>> 
>> 
>> 
>> 
>> 
>> On Oct 11, 2013, at 10:58 AM, Jakub Ostrowski wrote:
>> 
>>> Hi,
>>> 
>>> I'd like to point out an unusual behavior that happens with calculations which use the recently implemented OP AGSS09 opacity tables. I calculated models within mass range of 3 - 20 MS and for metallicity between 0.01 and 0.02 and there are problems with every model.
>>> 
>>> First of all, with OPAL AGSS09, OPAL GS98 and OP GS98 there is a helium blue loop for every calculated track while for OP AGSS09 there is none for any of them. This behavior itself doesn't necessary mean that something is wrong, but the other thing does: after the core helium abundance drops below about 1% it suddenly rises to about 3% and the energy produce from helium burning increases. Then it repeats itself again for a dozen of times or so. I attached a plot that shows this behavior for 15Ms and Z = 0.01, but this problem exists for every single model I calculated with OP AGSS09.
>>> 
>>> I discussed the problem with Radek who provided the tables. He confirmed that the problem is real and I'm sure he will soon provide his ideas.
>>> 
>>> My environment: MESA v5456 compiled with SDK on OS X 10.8.5. You can find the attaches inlist. The only things I changed there are opacity tables, mass and metallicity.
>>> 
>>> Cheers,
>>> Jakub
>>> 
>>> <LHe-Yc-15m-op-z0.01.pdf>
>>> <15m-z0.01-op-opal.pdf>
>>> <inlist_15m_op_f0010_z001>
>> 
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> 
> -- 
> J. Craig Wheeler
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