Re: [mesa-users] Change in evolutionary timescale between r8118 and r9575

[Pablo M. <pa...@gm...>]

Hi Matteo, my first recommendation would be to check for convergence of
your models. Using the same version of MESA, do you get the same lifetime
if you increase resolution by two and decrease your timesteps by a similar
factor? How many steps are you using to model the main sequence.

At this mass in particular you could be getting a small convective core as
well. Depending on your treatment of the convective boundary this can cause
odd discrepancies. You can for instance make some Kippenhahn plots to check
for this, either using the options available on PGSTAR for that, or some
python tools developed by some of us

https://github.com/orlox/mkipp
https://github.com/rjfarmer/mesaplot

In particular I'd recommend you use the Ledoux criterion with
semiconvection, by setting

use_ledoux_criterion = .true.
alpha_semiconvection = 1d0

Cheers

On Tue, Mar 28, 2017 at 10:03 AM, Matteo Dell'Omodarme <mat...@fa...
> wrote:

> Dear All,
>
> I'm performing some basic comparisons in order to extend (using MESA
> r9575) a
> dataset computed by means of MESA r8118.
> I'm noticing some differences in the evolutionary timescale between the two
> releases.
>
> The case study I'd like to discuss is M = 1.40 Msun, Z = 0.01894, Y =
> 0.2674.
> The inlist for the computations are attached to this message (inlist,
> inlist_default, and inlist-nr) [the control  photo_interval in r9575
> replaces
> the old photosteps], as well as the .net adopted.
>
> It turns out that the stellar evolution computed by r9575 is 2% faster than
> the one by r8118 (see attached plots). This is a very notable difference --
> all input being the same -- and it
> will have a relevant impact on grid-based estimates of stellar mass,
> radius, and age.
>
> I've no clue to trace the origin of the difference, since the release
> notes do
> not highlight some changes which could alter so much the evolutionary
> timescale.
>
> Could someone help by pointing out the changes (algorithms or default
> values) occurred between the two versions?
>
> Thanks in advance,
> Matteo Dell'Omodarme
>
> Sezione di Astronomia
> Università di Pisa
>
> ------------------------------------------------------------
> ------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> mesa-users mailing list
> mes...@li...
> https://lists.sourceforge.net/lists/listinfo/mesa-users
>
>


-- 
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD student, Argelander-Institut für Astronomie