[Mesa-users] Individual Chemical Abundances by number
fxt44 at mac.com
Sat Oct 10 16:49:50 EDT 2020
baryon number is an invariant under nuclear reactions.
so, define the abundance of species Y_i by
Y_i = N_i / N_b = n_i / n_b
N_i is the number of nucleons of isotope i,
N_b is the total number of baryons,
n_i is the number density (1/cm^3) of nucleons of isotope i, and
n_b is the total number density (1/cm^3) of baryons.
The number of baryons in isotope i (N_i * A_i) divided by the
total number of baryons N_b is the baryon fraction
X_i = N_i * A_i / N_b = Y_i * A_i
where A_i is the atomic number of isotope i.
sometimes the baryon fraction is called the mass fraction.
sum X_i = N_b / N_b = 1 .
define the baryon density (g/cm^3) as
rho_b = n_b * m_amu
where m_amu is the atomic mass unit (in g).
sometimes the baryon density is called the mass density rho.
you can likely take it from here to get what you want.
> On Oct 10, 2020, at 12:38 PM, Trust Otto via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> Dear MESA users,
> I am using MESA-version 12778 and interested in obtaining individual chemical abundances (from H to Ni) by number for 1.6 to 3.0 Msun MS stars. The individual chemical abundances I managed to get after editing the history_columns.list and profile_columns.list files and choosing an appropriate net are mass fractions. How can I get the individual chemical abundances by number?
> Thank you in advance.
> Otto Trust
> Department of Physics
> Mbarara University of Science and Technology
> P.O.Box 1410
> e-mails: trust.otto at yahoo.com/otrust at must.ac.ug
> mesa-users at lists.mesastar.org
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