[Mesa-users] Hydrogen core mass and radius

[Aaron Dotter]

Hi Pedro,

Please include mesa-users when you reply to emails on this list.

The He core (he_core_radius and he_core_mass) is defined by the H mass
fraction falling below some limit.

For the case you are interested in, we can't use the above definition, and
I don't think there is anything in history columns that will give you
exactly what you want.  But have a look at these:

   !## regions of strong nuclear burning

      ! 2 zones where eps_nuc > burn_min1 erg/g/s
      ! for each zone have 4 numbers: start1, start2, end2, end1
      ! start1 is mass of inner edge where first goes > burn_min1 (or -20
if none such)
      ! start2 is mass of inner edge where first zone reaches burn_min2
erg/g/sec (or -20 if none such)
      ! end2 is mass of outer edge where first zone drops back below
burn_min2 erg/g/s
      ! end1 is mass of outer edge where first zone ends (i.e. eps_nuc <
burn_min1)
      ! similar for the second zone

      epsnuc_M_1 ! start1 for 1st zone
      epsnuc_M_2 ! start2
      epsnuc_M_3 ! end2
      epsnuc_M_4 ! end1

      epsnuc_M_5 ! start1 for 2nd zone
      epsnuc_M_6 ! start2
      epsnuc_M_7 ! end2
      epsnuc_M_8 ! end1


      ! you might want to get a more complete list of burning regions by
using the following

      !burning_regions <integer>
         ! the <integer> is the number of regions to report
         ! there will be 2*<integer> columns for this in the log file, 2
for each region.
         ! the first column for a region gives
int(sign(val)*log10(max(1,abs(val))))
            ! where val = ergs/gm/sec nuclear energy minus all neutrino
losses.
         ! the second column for a region gives the q location of the top
of the region
         ! entries for extra columns after the last region in the star will
have a value of -9999
         ! all regions are included starting from the center, so the bottom
of one region
         ! is the top of the previous one.
         ! since we start at the center, the bottom of the 1st region is
q=0 and top of last is q=1.

         ! the columns in the log file will have names like 'burn_type_1'
and 'burn_qtop_1'


         ! if the star has too many regions to report them all,
         ! the smallest regions will be merged with neighbors for reporting
purposes only.


Otherwise you will have to make your own definition and add it to your
history file via run_star_extras.  There are tutorials,

http://mesa.sourceforge.net/run_star_extras.html#adding-history--profile-output


Good luck!

Aaron

On Wed, Aug 22, 2018 at 1:21 PM Pedro Nuno David Gomes <
pedro.david.gomes at ist.utl.pt> wrote:

> A 2018-08-22 17:24, Aaron Dotter escreveu:
>
> Hi Pedro,
>
> This will depend upon how you define the hydrogen core.  So, how do you
> define it?
>
> Aaron
>
> On Wed, Aug 22, 2018 at 11:26 AM Pedro Nuno David Gomes via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
>> Dear MESA users,
>>
>> Regarding the evolution of Main Sequence stars, how can I obtain as
>> output the fractional mass and radius of the hydrogen core?
>>
>> Thank you for your attention.
>> Regards,
>>
>> Pedro
>> _______________________________________________
>> mesa-users at lists.mesastar.org
>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>
> Hi Aaron,
>
> Thank you for your reply.
>
> I consider the core of a MS star to be the region in which nuclear fusion
> of hydrogen into helium is occuring. In what concerns MESA, I haven't
> defined anything regarding the core (sorry if I'm missing something
> obvious, but I only started working with MESA recently).
>
> Since the radius of the He core can be obtained for other evolution stages
> by uncommenting "he_core_radius" in history_columns.list, I imagined there
> could be something similar for H core. I'm trying to evolve a 1.5M_sun
> star until the subgiant branch.
>
> Thank you. Cheers,
>
> Pedro
>
>
>
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