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

[Natalija M]

Thank you both for the suggestions! I’ll try them out and see what I can
figure out. I’ll let you know if anything interesting comes up.

Best,
Natalija



On Mon, Mar 16, 2026 at 10:22 PM Farag, Ebraheem <ebraheem.farag at yale.edu>
wrote:

> 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> 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>
> 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> on behalf of
> Natalija M via Mesa-users <mesa-users at lists.mesastar.org>
> *Sent:* Monday, March 16, 2026 3:54 AM
> *To:* mesa-users at lists.mesastar.org <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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