[Mesa-users] Evolution of a 9M_sun ZAMS star up to to core collapse

Sat Apr 3 22:41:38 UTC 2021

Amar, remind me what MESA revision you're running?

Agreed with Bill -- getting a 9Msun star, especially stripped, to build an
Fe core and run all the way to core collapse without horribly excessive
overshooting is very hard! Your f and f0 values look fine and well within
the scope of what's often used; overshooting is a convenient hack to try to
match 3D convective boundaries anyway. Most of these controls control the
resolution (varcontrol --> time resolution, mesh_delta --> spatial
resolution) and at their face seem sensible as well. In fact for some
you're using higher resolution than the test_suite typically does, which is
good.

To me, the one change that's the most suspect is changing
mixing_length_alpha to such a low value (so, making convection very
inefficient) in inlist_to_si_burn.
I also don't have much intuition as to why it helps (but clearly it does).

By default (at least in the latest MESA revision), another control setting
alpha_mlt is
      x_ctrl(24) = 9d0 ! mass limit (Msun). ! use other_alpha_mlt only if
star_mass >= this limit.
So if you have mass loss on a 9Mzams star, then you won't be using the
core-envelope scheme implemented with the other x_ctrl's in
run_star_extras. I think turning off use_other_alpha_mlt here is perfectly
fine, since sometimes you can get weird effects when alpha changes sharply
within the H/He boundary layer for low-mass RSG's, and as I understand it,
the scheme was just devised to get both sensible core properties (alpha ~
1.5) and the envelope structure to matched observed RSG's (which typically
require alpha_H ~ 2-3).

However, 0.01 seems like an extremely low value for the mixing length
compared to the values between 1-4 typically seen in massive star
literature, so the question is: is this stellar engineering OK for your end
goal? One way to get a sense is to look at the resulting stellar structure.
Is there anything surprising? What is the core mass? What are the L/R/Teff?
Does the resulting star lie on a reasonable part of the HR diagram/resemble
any stripped massive stars observed in nature? Does the Tc - Rhoc evolution
follow a qualitatively similar track to other RSG models, or does it veer
off and become very degenerate? Another diagnostic you could do is to see
how different models made with alpha = 0.01 and 0.02 (before failure) and
0.005 look, to see how sensitive your solution is to this choice of alpha.

Hope this is helpful!

Cheers,
~Jared

On Sat, Apr 3, 2021 at 10:37 AM Bill Paxton via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Brilliant!   Well done!  Jared is great. 12M is about the limit of my
> willingness to wait for results that might never be coming.
>
> The challenge is to find interesting problems that are also within reach
> of what MESA can currently manage in the time you have available.
>
>
>
> On Apr 3, 2021, at 10:29 AM, amar at aries.res.in wrote:
>
> Dear Bill,
>
> Many thanks for your prompt reply. Here I wish to mention that a few
> months back, we were struggling to get going with a 12M_sun ZAMS star
> progenitor but with some changes, we could successfully model ( with
> excessive bits of help from Jared Goldberg ) the 12M_sun ZAMS star and
> further got successful STELLA calculations providing the light curves and
> velocity evolutions.
>
> With best regards,
> Amar
>
>
> ------------------------------
> *From: *paxton at kitp.ucsb.edu
> *To: *amar at aries.res.in
> *Cc: *mesa-users at lists.mesastar.org, Amararyan941 at gmail.com
> *Sent: *Saturday, April 3, 2021 10:48:21 PM
> *Subject: *Re: [Mesa-users] Evolution of a 9M_sun ZAMS star up to to core
> collapse
>
> just a quick comment:  i’ve never been able to get 9M beyond the
> off-center Neon flash.  Perhaps i’m just too impatient, but it takes longer
> than I’m willing to wait for the burning to make its way slowly to the
> center.  with more massive models, the neon ignition is at the center so
> things go smoothly.   you are welcome to try, but it might go easier if you
> can redefine your problem to 12M or more.
>
> cheers,
> bill
>
>
> On Apr 3, 2021, at 10:12 AM, Amar Aryan via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
> Dear MESA user team,
>
> I am trying to make a 9M_sun ZAMS model with Z=0.02 that explodes as a
> type IIb SN. Gladly, I could evolve the star up to the stage of Fe core
> infall, using the default *star/test_suit/example_make_pre_ccsn *with few
> modifications. Although I could evolve the model up to Fe core infall, I am
> not sure about a few parameters to be physical :
>
> Now here I briefly mention the changes in the inlist_files of
> *example_make_pre_ccsn *directory :
>
> a) In inlist_common, *varcontrol_target = 1d-3,*
>                            *mixing_length_alpha = 2.0*
> *            mixing_delta_coeff_for_highT = 2.5*
> *                                                              f = 0.007
>   (Not sure if this is allowed!)*
> *                                                             f0= 0.001*
>
> b) In  inlist_set_alpha_mlt, *x_ctrl(21) = 2.5*
> *                                           x_ctrl(22) = 1.5*
> *                                           x_ctrl(23) = 0.5*
>
> 1) In Inlist_to_zams, *varcontrol_target = 1d-5   *
>
> 2) In inlist_to_zams, *varcontrol_target = 1d-5*
>
> 3) In inlist_remove, *varcontrol_target = 1d-5, *
> *                                     mass_change = -1d-4*
> *                     star_H_mass_min_limit = 0.013*
>
> 4) In inlist_before_remove,  *!* *varcontrol_target = 1d-2   (Not used)*
> *                     Steps_to_take_before_terminate = 2*
>
> 5) In inlist_to_si_burn, *varcontrol_target = 5d-4,*
> *                              mixing_length_alpha = 0.01 (seems to be too
> low but anything greater than 0.01 did not worked, setting this to 0 also
> failed!!)*
> 6) In inlist_to_lgT9.9,* varcontrol_target = 5d-4 *
>
> Please provide your valuable suggestions regarding f, f0,
> mixing_lenth_alpha, and other major mistakes if any in the above parameters.
>
> With best regards,
> Amar
>
>
>
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
>
>
>
>
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20210403/f5b02d7d/attachment.htm>