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Magnetic field effects on nucleosynthesis and kilonovae from neutron star merger remnants

We investigate the influence of parametric magnetic field configurations of a hypermassive neutron star (HMNS) on electromagnetic (EM) observables, specifically the kilonova lightcurves and nucleosynthesis yields. We perform three-dimensional (3D) dynamical-spacetime general-relativistic magnetohydrodynamic (GRMHD) simulations, including a neutrino leakage scheme, microphysical finite-temperature equation of state (EOS), and an initial poloidal magnetic field. We find that varying the magnetic field strength and falloff impacts the formation of magnetized winds or mildy-relativistic jets, which in turn has profound effects on the outflow properties. All of the evolved configurations collapse to a black hole (BH) $\sim 21-23$ ms after the onset of the simulations, however, the ones forming jets may be considerably more effective at transporting angular momentum out of the system, resulting in earlier collapse times. Larger mass ejecta rates and radial velocities of unbound material characterise the systems that form jets. The bolometric light curves of the kilonovae and $r$-process yields change considerably with different magnetic field parameters. We conclude that the magnetic field strength and falloff have robust effects on the outflow properties and electromagnetic observables. This can be particularly important as the total ejecta mass from our simulations ($\simeq 10^{-3}\;M_{\odot}$) makes the ejecta from HMNS a compelling source to power kilonova through radioactive decay of $r$-process elements.