Using general-relativistic hydrodynamical simulations, we show that merging binary neutron stars can form hypermassive neutrons stars that undergo the one-arm spiral instability. We study the particular case of a dynamical capture merger where the stars have a small spin, as may arise in globular clusters, and focus on an equal-mass scenario where the spins are aligned with the orbital angular momentum. We find that this instability develops when postmerger fluid vortices lead to the generation of a toroidal remnant - a configuration whose maximum density occurs in a ring around the center-of-mass - with high vorticity along its rotation axis. The instability quickly saturates on a time scale of ∼10 ms, with the m=1 azimuthal density multipole mode dominating over higher modes. The instability also leaves a characteristic imprint on the postmerger gravitational wave signal that could be detectable if the instability persists in long-lived remnants.
|Original language||English (US)|
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|State||Published - Dec 30 2015|
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Physics and Astronomy (miscellaneous)