[Mesa-users] Re Frank Timmes Response: Carbon Dredge-up/Third Dredge-up Efficiency and Timing in 1.3 Msun, Z=0.008 Model

[KAYLA MARTIN]

Hi Frank,

Thank you for your response, and for the helpful resources!

I will implement the resolution controls used in the c13_pocket test suite
case to my model.

Regards,
Kayla.


On Mon, Aug 26, 2024 at 2:44 AM Frank Timmes <fxtimmes at gmail.com> wrote:

> the recent article
> https://academic.oup.com/mnras/article/527/4/9643/7491079 is also
> relevant.
>
> fxt
>
>
>
>
> On Aug 25, 2024, at 9:03 AM, Frank Timmes <fxtimmes at gmail.com> wrote:
>
> hi kayla,
>
> take a look at mesa I, section 7.2.1, and especially figure 27.
>
> then take a look at the c13_pocket test suite case,
> https://docs.mesastar.org/en/24.08.1/test_suite/c13_pocket.html#c13-pocket
> , which covers the third dredge-up for a ~0.9 msun structure. note the
> relative smallness of the spatial/temporal resolution controls that are
> needed to ensure the thermal pulse cycles and the c13 pocket are well
> resolved.
>
> fxt
>
>
>
>
> On Aug 25, 2024, at 12:23 AM, KAYLA MARTIN via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
> Hi all,
>
> I am having some issues with the efficiency of the third dredge-up to
> increase the C/O ratio in my star. I have specified the relevant model
> parameters currently in my inlist at the bottom of this email for reference.
>
> The ultimate goal of my model is to become carbon rich (i.e., C/O > 1) by
> a total stellar mass of ~0.9 solar masses (after approx. 7-8 thermal
> pulses). The initial C/O ratio in the model is 0.23.
>
> Currently, my model achieves C/O>1 only after ALL thermal pulses (approx.
> 9) have occurred, at a much lower total mass of ~0.6 solar masses. I
> believe this implies that the third dredge-up is ineffective until after
> the thermal pulse stage.
>
> I am seeking suggestions on how I may trigger the third dredge up at an
> earlier time in my model, to achieve C/O>1 closer to a total mass of 0.9
> solar masses.
>
> Thank you in advance! :)
>
>
> Parameter settings for context...
>
> My model is a 1.3 solar mass star, with initial Z=0.008 (gs98 and gs98_co
> base compositions). The model has the following specified initial
> composition:
>    •
> initial_h1 = 0.731924
>    • initial_h2 = 0.000076
>    • initial_he3 = 0.0000846
>    • initial_he4 = 0.2599154
>    • z_fraction_o = 0.53
>    • z_fraction_c = 0.123
> **The rest of the z_fractions are in other elements and are not so
> important to my goal.
> My mixing parameters are set such that:
>    •
> mixing_length_alpha=1.75
>    • MLT_option='Cox' (as I want diffusive mixing)
>    • use_Ledoux_criteron=.true.
>    • alpha_semiconvection=0.04
>    • thermohaline_coeff=2.0
>    • overshoot_scheme(1)='exponential'
>    • overshoot_zone_type(1), overshoot_zone_loc(1), and
> overshoot_bdy_loc(1)='any'
>    • overshoot_f(1)=0.025 for pre-AGB phases and 0.008 for AGB onward
>    • overshoot_f0(1)=0.005 for pre-AGB phases and 0.004 for AGB onward
>
> I am currently using a Reimers wind scheme with scaling factor 0.477 on
> the RGB, and a Blocker wind scheme with scaling factor 0.01 (and have also
> tried 0.02) on the AGB.
>
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
>
>
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