[Mesa-users] Questions about convective mixing during a proton ingestion event (when the He-convective zone engulfs H material)

[Farag, Ebraheem]

Hi Guo,

It is hard to make an apples to apples comparison, as the authors have conducted their study in an entirely different stellar evolution software instrument (STAREVOL). It is likely that this type of behavior is highly sensitive toward the adopted convection physics (especially the convective boundary mixing schemes), to note just one among many differences.

I'm not sure if your MESA inlists are perfectly replicating the physics adopted in the Choplin paper, however it important to note that they have different convective boundary mixing schemes than the defaults offered in MESA. See all of section (2), and eqn (9) in https://ui.adsabs.harvard.edu/abs/2018A%26A...609A..29G/abstract. As one of the adopted approaches is a slight modification/extension of the herwig (1997) exponential overshooting scheme: In principle one could include a similar boundary mixing routine in MESA using the run_star_extras using the "other_overshooting_scheme". This is where MESA excels in its modularity.

-EbF

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From: Mesa-users <mesa-users-bounces at lists.mesastar.org> on behalf of Guo Li via Mesa-users <mesa-users at lists.mesastar.org>
Sent: Tuesday, February 11, 2025 3:25 AM
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Subject: [Mesa-users] Questions about convective mixing during a proton ingestion event (when the He-convective zone engulfs H material)

Hi all,
I hope this message finds you well.

I am simulating a 1Msun，[Fe/H]=-2.5 stellar evolution model based on the literature https://doi.org/10.1051/0004-6361/202040170. During the second Thermal Pulse (TP), the He-convective zone approaches the H-shell and engulfs H material, resulting in a proton ingestion event. After H is mixed into the He-convective zone, the literature indicates that the location with the highest H-burning energy production is in the middle of the He-convective zone, where energy accumulation leads to the splitting of the He-convective zone. However, in my results, the highest energy production occurs at the bottom of the convective zone, preventing the He-convective zone from splitting.

What could be the reason for this discrepancy? I suspect that the H profile gradient within the He-convective zone in my results is too small. Is this due to overly rapid convective mixing, or are there other reasons? The following figures show the mass fraction and energy profiles after the proton ingestion event.

[cid:5b1c81ad$1$194f41cf049$Coremail$liguo070923$163.com]

I appreciate your assistance and look forward to your response.

Thank you!

Best regards,
Guo Li
National Astronomical observatories,CAS
[https://count.mail.163.com/beacon/webmail.gif?type=webmail_mailtrace&guid=pre_6a2cf05f884254ae50272cc4b157050e]
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