Kavli Affiliate: Renxin Xu
| First 5 Authors: Guoqing Zhen, Helei Liu, Akira Dohi, Guoliang Lü, Nobuya Nishimura
| Summary:
In this study, we calculate for the first time the impacts of neutron
star(NS) structure on the type I X-ray burst ashes using the texttt{MESA}
code. We find an increased mass fraction of the heavier elements with
increasing surface gravity (increase mass or decrease radius), resulting in a
higher average mass number ($A_{rm ash}$) of burst ashes (except for higher
mass NS due to the competition between the envelope temperature and the
recurrence time). The burst strength ($alpha$) increases as surface gravity
increases, which indicates the positive correlation between $A_{rm ash}$ and
$alpha$ with changes in surface gravity. If the $alpha$ value is higher,
heavier $p$-nuclei should be produced by the type I X-ray burst
nucleosynthesis. Besides, the effects of various burst input parameters, e.g.
base heating ($Q_{rm b}$), metallicity ($Z$) and some new reaction rates are
calculated for comparison. We find that the heavier nuclei synthesis is
inversely correlated to the base heating/metallicity, the smaller the base
heating/metallicity, the greater the mass fraction of the heavier elements. The
$alpha$ value decreases as $Q_{rm b}$ or $Z$ decreases, which also indicates
the positive correlation between $A_{rm ash}$ and $alpha$ with variation in
$Q_{rm b}$ or $Z$. The new reaction rates from the $(p,gamma)$ reactions on
$^{17}rm{F}$, $^{19}rm{F}$, $^{26}rm{P}$, $^{56}rm{Cu}$, $^{65}rm{As}$,
and $(alpha,p)$ reaction on $^{22}rm{Mg}$ have only minimal effects on burst
ashes. In hydrogen-rich X-ray binary systems, nuclei heavier than
$^{64}rm{Ge}$ are fertile produced with larger NS mass, smaller NS radius,
smaller base heating and smaller metallicity.
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