*Astron. Astrophys. 326, 1001-1012 (1997)*
## Appendix A: species conservation
### A.1. Mass fraction
Consider a species *i* whose mass fraction in the accreted
matter and in the star at shell *j* are
and , respectively. The total mass of element
*i* after accretion is given by and
represent a summation over the *n* shells of the model:
So, we have
and finally we obtain
### A.2. Rescaled abundances
The new fractional mass derived alone
refers to the old mesh point. However, modifications of the mass
profile can result in changes in the mesh points. If *k* is the
shell number such that where subscript
*j* refers to the old mesh points and *k* to the current
ones, the interpolated composition at mass is
then
© European Southern Observatory (ESO) 1997
Online publication: April 8, 1998
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