[Mesa-users] Differences between MESA r10398 and 25.12.1 for rotating very massive stars

[Farag, Ebraheem]

Very interesting!

I would conject that these large changes are likely due to differences in input physics. In addition to the examples raised by Jared, differences in the default nuclear reaction rates being adopted could serve as another systematic. See:
https://docs.mesastar.org/en/25.12.1/changelog.html#id27

If you can isolate all these variables, it would be interesting to see if your models are still substantially different! It's certainly important for us to be able to identify what if any differences between mesa versions can lead to different outcomes.


-EbF
________________________________
From: Jared Goldberg (Guest Researcher) <jgoldberg at flatironinstitute.org>
Sent: Monday, March 16, 2026 4:49 PM
To: Natalija M <nm.mladenovic at gmail.com>
Cc: Farag, Ebraheem <ebraheem.farag at yale.edu>; mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>
Subject: Re: [Mesa-users] Differences between MESA r10398 and 25.12.1 for rotating very massive stars

Unfortunately, a LOT has changed since r10398. Many of these changes are motivated by, e.g. energy conservation. Sometimes this has come at the expense of other things. The output in both cases looks pretty poorly sampled in time; perhaps that is contributing as well?

It seems in part like differences may arise if winds were stronger in the old revision, since at Zsolar the old revision ends less luminous (lost more mass) and at SMC metallicity it looks like it loses its envelope quickly for the old revision whereas the new revision looks like it does have a main sequence, of sorts. Places to look besides overshooting: How does Mdot versus time compare? And surface abundances? Core abundances?

Best,
~Jared

On Mon, Mar 16, 2026 at 4:36 PM Natalija M via Mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>> wrote:

Hello Ebraheem,

Thank you for the quick reply.

I did try different values of the overshooting parameter. From the tests so far, it seems that f = 0.345 reproduces the solar metallicity case better compared to the old models. However, in general the difference between f = 0.345 and f = 0.25 remains relatively small through most of the evolution and only becomes more noticeable toward the very end of the evolution for the new version. Because of this, I am not sure that the overshooting alone explains why the models from the older version evolve toward higher effective temperatures in the HR diagram almost immediately.

I’ve attached HR diagrams for both the solar and SMC metallicity cases with the different overshooting values.


Best regards,

Natalija


On Mon, Mar 16, 2026 at 7:22 PM Farag, Ebraheem <ebraheem.farag at yale.edu<mailto:ebraheem.farag at yale.edu>> wrote:
Hello Natalija,

I notice you are using different amounts of overshoot in each inlist, perhaps that explains some of the differences you are seeing?

-EbF
________________________________
From: Mesa-users <mesa-users-bounces at lists.mesastar.org<mailto:mesa-users-bounces at lists.mesastar.org>> on behalf of Natalija M via Mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>>
Sent: Monday, March 16, 2026 3:54 AM
To: mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org> <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>>
Subject: [Mesa-users] Differences between MESA r10398 and 25.12.1 for rotating very massive stars


Dear MESA users,

I am currently trying to switch from r10398 to 25.12.1, and while doing so I noticed some differences in the results.

I evolved rotating very massive stars with low metallicity using the inlists attached below (which are quite similar for both versions). For solar metallicity, the results are in very good agreement between the two versions. However, for lower metallicities, the models evolve very differently, as illustrated in the HR diagram. I am not sure what in the older version leads to this behavior.

I would greatly appreciate any help or guidance.

Best regards,
Natalija Mladenović

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