Favorable conditions for heavy element nucleosynthesis in rotating proto-magnetar winds

Favorable conditions for heavy element nucleosynthesis in rotating proto-magnetar winds

The neutrino-driven wind cooling phase of proto-neutron stars (PNSs) follows successful supernovae. Wind models without magnetic fields or rotation fail to achieve the necessary conditions for production of the third $r$-process peak, but robustly produce a weak $r$-process in neutron-rich winds. Using 2D magnetohydrodynamic simulations with magnetar-strength magnetic fields and rotation, we show that the PNS rotation rate significantly affects the thermodynamic conditions of the wind. We show that high entropy material is quasi-periodically ejected from the closed zone of the PNS magnetosphere with the required thermodynamic conditions to produce heavy elements. We show that maximum entropy $S$ of the material ejected depends systematically on the magnetar spin period $P_{star}$ and scales as $S propto P_{star}^{-5/6}$ for sufficiently rapid rotation. We present results from simulations at a constant neutrino luminosity representative of $sim 1-2$ s after the onset of cooling for $P_{star}$ ranging from 5 ms to 200 ms and a few simulations with evolving neutrino luminosity where we follow the evolution of the magnetar wind until $10-14$ s after the onset of cooling. We estimate at magnetar polar magnetic field strength $B_0=3times 10^{15}$ G, $10^{15}$ G, and $5times 10^{14}$ G that neutron-rich magnetar winds can respectively produce at least $sim 2-5times 10^{-5}$ M$_{odot}$, $sim 3-4times 10^{-6}$ M$_{odot}$, and $sim 2.5times 10^{-8}$ M$_{odot}$ of material with the required parameters for synthesis of the third $r-$process peak, within $1-2$ s, 10 s, and 14 s in that order after the onset of cooling. We show that proton-rich magnetar winds can have favorable conditions for production of $p-$nuclei, even at a modest $B_0=5times 10^{14}$ G.The neutrino-driven wind cooling phase of proto-neutron stars (PNSs) follows successful supernovae. Wind models without magnetic fields or rotation fail to achieve the necessary conditions for production of the third $r$-process peak, but robustly produce a weak $r$-process in neutron-rich winds. Using 2D magnetohydrodynamic simulations with magnetar-strength magnetic fields and rotation, we show that the PNS rotation rate significantly affects the thermodynamic conditions of the wind. We show that high entropy material is quasi-periodically ejected from the closed zone of the PNS magnetosphere with the required thermodynamic conditions to produce heavy elements. We show that maximum entropy $S$ of the material ejected depends systematically on the magnetar spin period $P_{star}$ and scales as $S propto P_{star}^{-5/6}$ for sufficiently rapid rotation. We present results from simulations at a constant neutrino luminosity representative of $sim 1-2$ s after the onset of cooling for $P_{star}$ ranging from 5 ms to 200 ms and a few simulations with evolving neutrino luminosity where we follow the evolution of the magnetar wind until $10-14$ s after the onset of cooling. We estimate at magnetar polar magnetic field strength $B_0=3times 10^{15}$ G, $10^{15}$ G, and $5times 10^{14}$ G that neutron-rich magnetar winds can respectively produce at least $sim 2-5times 10^{-5}$ M$_{odot}$, $sim 3-4times 10^{-6}$ M$_{odot}$, and $sim 2.5times 10^{-8}$ M$_{odot}$ of material with the required parameters for synthesis of the third $r-$process peak, within $1-2$ s, 10 s, and 14 s in that order after the onset of cooling. We show that proton-rich magnetar winds can have favorable conditions for production of $p-$nuclei, even at a modest $B_0=5times 10^{14}$ G.