[Mesa-users] Models failing to reach core collapse

[Rob Farmer]

Hi,

I see you've removed overshoot from your models. I find that having even a
little bit of overshoot usually helps mesa evolve a model more efficiently,
as it smooths the composition boundaries. Also you've removed the
use_Ledoux_criterion=.true. so your using the default
use_Ledoux_criterion=.false. which means schwarzschild convection
boundaries. Again i've found ledoux to make the evolution easier (but this
depends on what physics you want to test, if you want to change it)

The other thing to do is work out what is happening inside the star that is
causing problems. Kippenhan/abundance profile/mixing profile plots can help
here to see how the burning/mixing is behaving and if it seems to get stuck
somewhere particular (core burning? shell burning? which fuel?) which can
help refine what you need to change to get the model working.

I'd also look at what is limiting the timetsep. This is given by the string
in the last entry of the terminal output for a step (called dt_limit). That
limit can then be compared to the names here
http://mesa.sourceforge.net/controls_defaults.html#timestep_controls and
that will give you the timestep control that is currently limiting your
evolution.

Rob


On Thu, 17 Jan 2019 at 05:42, Jamie Tayar <jtayar at hawaii.edu> wrote:

> Hi Taylor,
> This isn't really my area of expertise, so I'll let someone else comment
> on the details of your models, but 15 solar masses is right around where
> the 'islands of explodability' start to show up (e.g. Figure 5 of
> https://arxiv.org/abs/1602.05956 or Figure 8 of
> https://arxiv.org/pdf/1710.03243.pdf), and some fraction of models never
> reach the sort of compactness that indicates a successful collapse, so
> there's a possibility that what you're seeing is physics and not numerics.
> Apologies if you've already thought of that,
> Jamie
>
> On Wed, Jan 16, 2019 at 6:25 PM Taylor Jacovich via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
>> Hello all,
>>
>> Have run into an issue with the current version of MESA where stars with
>> a specific mass will never reach core-collapse (fe_core_infall > 10**3km/s
>> stopping condition).  A full description of the issue and all the model
>> data can be found here: https://gitlab.com/wind-loss-testing/readme .
>>
>> The reader’s digest version is that stars with a certain mass (eg.
>> 15.0Msun) will get stuck at a sub-Chandrasekhar mass iron core and happily
>> coast for weeks at a time.  Meanwhile masses directly around the ones that
>> fail to collapse (eg. 14.9Msun and 15.1Msun) will collapse without fail.
>> We are using Farmer’s inlists that were designed to help with
>> explodability, and the only parameter we change between runs is the mass.
>> Any suggestions on new parameters to try or other options that may
>> relieve the issue are much appreciated. Inlists are attached below, or you
>> can clone from this directory
>> https://gitlab.com/wind-loss-testing/windloss-template to have an
>> identical experience.
>>
>> Thank you,
>>
>>
>> Taylor Jacovich
>>
>>
>> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users
>
>
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