[Mesa-users] Tip of the Red Giant Branch

Wed Oct 13 15:28:57 UTC 2021

Hi Mitchell,

You're referring to "i-Band" and "I band" but these mean different things.
It might be helpful if you could clarify what bandpass you're expecting.
Are you talking about the uppercase I of the Johnson-Cousins UBVRI?  Or are
you talking about the lowercase i of Thuan-Gunn (Sloan) ugriz?  MESA gets
its bolometric correction from the Lejeune et al. table that lives in
mesa/data/colors_data/.  It is not state-of-the-art by any means but it
should be (sort of) reasonable for this purpose.  FWIW, that table is
providing uppercase Johnson-Cousins I.

I second Frank's recommendation to look closely at the Serenelli+ 2017
paper.  You can compare your results with those given in Table 2 using just
the luminosity at the tip.  That removes the uncertainty of which "I-band"
we're talking about.

Aaron

On Wed, Oct 13, 2021 at 10:02 AM Mitchell Dennis <mtde226 at hawaii.edu> wrote:

> Hi Frank,
>
>
>
> One of the stars that didn’t reach the desired peak had a mass of 0.8
> Msolar and a metallicity of 0.0008. The i-band magnitude is one of the
> outputs of MESA. It is turned on with the control abs_mag I in the
> history_columns.list file and the default history_columns.list file
> indicates it is an absolute magnitude. I am not sure how MESA is
> specifically calculating the I band magnitude.
>
>
>
> I changed the mesh_delta_coeff = 0.5 and max_dq = 5d-4 to adjust the
> resolution which improved the results I was seeing. Should these steps be
> sufficient? I thought MESA would automatically reduce the timesteps?
>
>
>
> At 0.855Msolar, Metallicity=.008, and Helium Abundance = 0.24 my i-Band
> magnitude only reaches -3.3. I have attached the inlist that got this
> result.
>
>
>
> Best,
>
> Mitchell
>
>
>
> *From: *Francis Timmes <fxt44 at mac.com>
> *Sent: *Monday, October 11, 2021 6:14 PM
> *To: *Mitchell Dennis <mtde226 at hawaii.edu>
> *Cc: *Frank Timmes <fxt44 at mac.com>; mesa-users
> <mesa-users at lists.mesastar.org>
> *Subject: *Re: [Mesa-users] Tip of the Red Giant Branch
>
>
>
> hi mitchell,
>
>
>
> give an example of a mass and metallicity that did not
>
> reach the desired peak i-band magnitude. also, how are
>
> the i-band absolute magnitudes being calculated?
>
>
>
> > Do you know of a way to be sure that I’ve reached the RGB tip?
>
>
>
>
>
> smaller timesteps are usually advantageous, as is a run_star_extras
>
> to ensure smaller timesteps around the peak luminosity / helium ignition.
>
>
>
>
>
> aldo serenelli et al's 2017 article
>
>
>
> https://ui.adsabs.harvard.edu/abs/2017A%26A...606A..33S/abstract
>
>
>
> is all-around super awesome and much can be learned from it
>
> when attempting to build similar models using mesa.
>
>
>
> fxt
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> > On Oct 7, 2021, at 7:40 PM, Mitchell Dennis <mtde226 at hawaii.edu> wrote:
>
> >
>
> > Dear MESA Users,
>
> >
>
> > I am running more follow up tests, and I was wondering if anyone has an
> inlist they would be willing to share for population II stars that yields
> an iBand magnitude of ~-4.0 at the tip of the red giant branch.
>
> >
>
> > Best Regards,
>
> > Mitchell T Dennis
>
> > Graduate Student
>
> > UH Manoa – Institute for Astronomy
>
> >
>
> > From: Mitchell Dennis
>
> > Sent: Friday, October 1, 2021 2:11 AM
>
> > To: Adrian Ayala
>
> > Cc: mesa-users at lists.mesastar.org
>
> > Subject: RE: [Mesa-users] Tip of the Red Giant Branch
>
> >
>
> > Dear Adrian,
>
> >
>
> > I used a wide grid of different metallicities and masses. While some of
> the models did reach -4.1 many of them did not even though the research
> papers I read state metallicity and mass shouldn’t affect the iBand
> magnitude once at the TRGB. Do you know of a way to be sure that I’ve
> reached the RGB tip?
>
> >
>
> > Best,
>
> > Mitchell
>
> >
>
> > From: Adrian Ayala
>
> > Sent: Friday, October 1, 2021 12:16 AM
>
> > To: mesa-users at lists.mesastar.org
>
> > Subject: Re: [Mesa-users] Tip of the Red Giant Branch
>
> >
>
> > Dear Mitchell,
>
> >
>
> > you should interpolate between different tracks with different
>
> > metallicities and masses in order to reproduce the observed values. Did
>
> > you try this?
>
> >
>
> > Best
>
> >
>
> > On 01/10/2021 12:13, Adrian Ayala wrote:
>
> > > Dear Mitchell,
>
> > >
>
> > >
>
> > > On 01/10/2021 11:04, Francis Timmes via Mesa-users wrote:
>
> > >> hi mitchell,
>
> > >>
>
> > >>> Is this typical for MESA at the TRGB ...
>
> > >>
>
> > >> mesa is a tool, not a model. i note that the inlist for your model
>
> > >> relies entirely on the default mass and temporal resolution criteria.
>
> > >> these default settings may be good enough for a nightly test suite
> case,
>
> > >> but they are probably not good enough for publication quality science.
>
> > >> best practices includes varying the default settings:
>
> > >>
>
> > >> https://docs.mesastar.org/en/latest/using_mesa/best_practices.html
>
> > >>
>
> > >> others can chime in on color filters ...
>
> > >>
>
> > >> fxt
>
> > >>
>
> > >>
>
> > >>
>
> > >>
>
> > >>
>
> > >>
>
> > >>
>
> > >>> On Sep 30, 2021, at 5:32 PM, Mitchell Dennis <mtde226 at hawaii.edu>
>
> > >>> wrote:
>
> > >>>
>
> > >>> Dear MESA Mailing List,
>
> > >>>   I am doing work on stars at the tip of the red giant branch, and
>
> > >>> although several research papers cite an iBand Magnitude of -4.1
>
> > >>> with a theoretical iBand Magnitude of ~-4, many of my models only
>
> > >>> reach an iBand Magnitude of -3.8. Is this typical for MESA at the
>
> > >>> TRGB, or am I missing a correction that I need to apply to the MESA
>
> > >>> absolute magnitude iBand output?
>
> > >>>   My current stopping condition is the power_he_upper_burn_limit
>
> > >>> which is set to 1.0d6. Typical mass, metallicity and helium
>
> > >>> abundance are 1.0, 0.0006 and 0.25.
>
> > >>>   I’ve attached a copy of my inlist which is based on the test_suite
>
> > >>> he_core_flash, and my run_star_extras file is unmodified.
>
> > >>>   Do you have any suggestions for determining whether a model will
>
> > >>> flash or not?
>
> > >>>   Thanks for the help
>
> > >>>   Best Regards,
>
> > >>> Mitchell T Dennis
>
> > >>> Graduate Student
>
> > >>> UH Manoa – Institute for Astronomy
>
>
>
>
> _______________________________________________
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>
>
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