[mesa-users] off-center Ne and O burning (again…)
Tuguldur Sukhbold
sukhbold at ucolick.org
Sun Apr 21 20:06:25 EDT 2013
thanks everyone for the fruitful discussion!
I have just tried my 15Msun with this parameter completely turned off, and my alpha_mlt=2 case is burning Ne and O in the core nicely with 4906! In the alpha_mlt=1 case, the CO core got a bit larger compared to my older run, but it wasn't big enough to overcome the off-center burning.
In my understanding, decrease of this parameter should produce a larger CO core, thus promoting regular central Ne and O burning. But I am a bit confused about why in version 4798, where this parameter was set to 1.0, I was able to get central burning.
MESA version alpha_mlt=1 alpha_mlt=2 prune_bad_cz_min_Hp_height
4798 y n 1.0
4906 y y 0.1
4906 y n 0.0
4917 y n 0.1(?)
Tuguldur
On Apr 21, 2013, at 1:00 PM, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
> Hi Stan,
>
> good advice. I went part way by reducing that parameter, but your
> suggestion is to turn it off completely -- which can be done by setting
>
> prune_bad_cz_min_Hp_height = 0
>
> along the same lines, it would be worth changing the following controls to .false.
>
> remove_mixing_glitches = .true. ! if true, then okay to remove gaps and singletons
> okay_to_remove_mixing_singleton = .true.
>
> Let's try it. Tug, Jakob, Josh, and others: please give this a try and let us know.
> I'll run the mesa test suite with these changes and see what happens there.
>
> Bill
>
>
>
>
>
> On Apr 21, 2013, at 12:43 PM, Stan Woosley wrote:
>
>> Just a thought. When semi convection is small or turned off in a code
>> the response is often to create many small alternating convection zones,
>> often only a few zones thick. These come and go out of phase and
>> act as a staircase that can mimic the effects of semiconvective mixing. I think
>> Icko Iben first saw this many years ago.
>>
>> Anyway, it may not be a good scheme to ignore convection anywhere
>> that the gradients say it should occur, even if its just a few zones.
>>
>> Stan
>>
>>
>>
>> On Apr 21, 2013, at 12:52 AM, Jakub Ostrowski <ostrowski at astro.uni.wroc.pl> wrote:
>>
>>> Hi!
>>>
>>> I'm working almost exclusively on 15 M_s models and I have found quite a big difference between the v4906 and previous ones too - but somewhere else than you.
>>>
>>> I studied properties of models after depletion of central H, logTeff ~ 4.30, logL ~ 4.63. The behavior of Brunt-Vaisala frequency is much smoother in v4906 than before and finally now there is convection where it should be according to behavior of gradients.
>>>
>>> And this is due to one change in controls.default. Now there is
>>>
>>> prune_bad_cz_min_Hp_height = 0.1 ! lower limit on radial extent of cz
>>>
>>> whereas previously the value was 1.0. I don't know if this is useful for you but for me this previously overlooked parameter made a huge change in case of my model. But it seems there is no dramatic influence on the shape of track on HRD.
>>>
>>> Take care,
>>> Jakub
>>>
>>> On 21 kwi 2013, at 06:59, Tuguldur Sukhbold <sukhbold at ucolick.org> wrote:
>>>
>>>> Dear MESA users,
>>>>
>>>> I am getting 2 different results with the exact same inlist for two different versions of the code: 4798 and the current 4906. Since MESA is constantly being developed, I understand that we should expect changes between the versions. However I am little surprised to see such a 'big' change in two releases came out almost one after the other.
>>>>
>>>> The attached plot shows the central T-Rho plane evolution for 15Msun model with the following simple inlist:
>>>>
>>>> &star_job
>>>>
>>>> mesa_dir = ''
>>>> create_pre_main_sequence_model = .true.
>>>>
>>>> set_rate_c12ag = 'Buchmann'
>>>> num_special_rate_factors = 1
>>>> reaction_for_special_factor(:) = 'r_c12_ag_o16'
>>>> special_rate_factor(1) = 1.2
>>>>
>>>> eos_file_prefix = 'mesa'
>>>> kappa_file_prefix = 'gs98'
>>>>
>>>> / !end of star_job
>>>>
>>>> &controls
>>>>
>>>> initial_mass = 15
>>>> initial_Z = 0.02
>>>> initial_Y = 0.25
>>>>
>>>> mixing_length_alpha = 2
>>>>
>>>> RGB_wind_scheme = 'Nieuwenhuijzen'
>>>> AGB_wind_scheme = ''
>>>> RGB_to_AGB_wind_switch = 1d-4
>>>> Nieuwenhuijzen_wind_eta = 1.0d0
>>>>
>>>> photostep = 50
>>>> profile_interval = 25
>>>> history_interval = 1
>>>> terminal_interval = 10
>>>> write_header_frequency = 10
>>>>
>>>> !hign
>>>> ! xa_central_lower_limit_species(1) = 'h1'
>>>> ! xa_central_lower_limit(1) = 0.72
>>>> !hdep
>>>> ! xa_central_lower_limit_species(1) = 'h1'
>>>> ! xa_central_lower_limit(1) = 0.01
>>>> !heign
>>>> ! xa_central_upper_limit_species(1) = 'c12'
>>>> ! xa_central_upper_limit(1) = 0.01
>>>> !hedep
>>>> ! xa_central_lower_limit_species(1) = 'he4'
>>>> ! xa_central_lower_limit(1) = 0.01
>>>> !cign
>>>> ! log_center_temp_limit = 8.69897 !0.5d8K
>>>> !cdep
>>>> log_center_temp_limit = 9.07918 !1.2d9K
>>>> !odep
>>>> ! xa_central_lower_limit_species(1) = 'o16'
>>>> ! xa_central_lower_limit(1) = 0.05
>>>>
>>>> /
>>>>
>>>> If you guys remember, I have previously brought up the issue of off-center O burning, in the case of alpha_mlt = 1, in version 4798. This behavior was gone if I set this parameter to alpha_mlt = 2, as it creates a larger CO core. However, when I try to recreate the older results with the current version of MESA - 4906 - I am facing the off-center burning issue again with alpha_mlt = 2.
>>>>
>>>> In the response to my previous email, Bill has reported that he got the same result (no off-center burning) with alpha_mlt=2 in his version of MESA - 4917.
>>>>
>>>> MESA version alpha_mlt=1 alpha_mlt=2
>>>> 4798 y n
>>>> 4906 y y
>>>> 4917 y n
>>>>
>>>> (yes/no to off-center Ne and O burning)
>>>>
>>>> I haven't seen anything in the release email from Bill for 4906, that might be relevant to what I see here.
>>>>
>>>> In general, 15Msun is a funny mass in MESA. It is sitting on the border of two different paths of evolutions of CO core: (1) degeneracy is important and off-center burnings of Ne and O as we've seen (2) degeneracy effects are no longer important and everything ignites in the center first. In other words, 15Msun model essentially with all the default settings, is producing a CO core mass that borderlines these two paths. This is why changing parameters here and there are producing these rather big changes for this 15Msun case. I don't think one will see this behavior in bigger mass models in any version of the code with any alpha_mlt, simply because the CO core will be big enough.
>>>>
>>>> From my experience, this funny mass is usually much lower in other codes, more like in the 8-12Msun range.
>>>>
>>>> Tuguldur
>>>>
>>>>
>>>>
>>>> <inc.png>
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