Hypermassive Neutron Star Disk Outflows and Blue Kilonovae

Understand

We study mass ejection from accretion disks around newly-formed hypermassive neutron stars (HMNS).

• Standard kilonova model fits to GW170817 require at least a lanthanide-poor ('blue') and lanthanide-rich ('red') component.
• The existence of a blue component has been used as evidence for a HMNS remnant of finite lifetime, but average disk outflow velocities from existing long-term HMNS simulations fall short of the inferred value ($\sim 0.25c$) by a factor of $\sim 2$.
• Here we use time-dependent, axisymmetric hydrodynamic simulations of HMNS disks to explore the limits of the model and its ability to account for observations.