Systematic exploration of heavy element nucleosynthesis in protomagnetar outflows

Kavli Affiliate: Shunsaku Horiuchi

| First 5 Authors: Nick Ekanger, Mukul Bhattacharya, Shunsaku Horiuchi, ,

| Summary:

We study the nucleosynthesis products in neutrino-driven winds from rapidly
rotating, highly magnetised and misaligned protomagnetars using the nuclear
reaction network SkyNet. We adopt a semi-analytic parameterized model for the
protomagnetar and systematically study the capabilities of its neutrino-driven
wind for synthesizing nuclei and eventually producing ultra-high energy cosmic
rays (UHECRs). We find that for neutron-rich outflows ($Y_e<0.5$), synthesis of
heavy elements ($overline{A}sim 20-65$) is possible during the first $sim
10$ seconds of the outflow, but these nuclei are subjected to
composition-altering photodisintegration during the epoch of particle
acceleration at the dissipation radii. However, after the first $sim 10$
seconds of the outflow, nucleosynthesis reaches lighter elements
($overline{A}sim 10-50$) that are not subjected to subsequent
photodisintegration. For proton-rich ($Y_e geq 0.5$) outflows, synthesis is
more limited ($overline{A}sim 4-15$). These suggest that while protomagnetars
typically do not synthesize nuclei heavier than second r-process peak elements,
they are intriguing sources of intermediate/heavy mass UHECRs. For all
configurations, the most rapidly rotating protomagnetars are more conducive for
nucleosynthesis with a weaker dependence on the magnetic field strength.

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