TY - JOUR
T1 - Equation of state effects and one-arm spiral instability in hypermassive neutron stars formed in eccentric neutron star mergers
AU - East, William E.
AU - Paschalidis, Vasileios
AU - Pretorius, Frans
N1 - Funding Information:
We thank Stuart Shapiro for access to the equilibrium rotating NS code. This work was supported by NSF grant PHY-1607449, the Simons Foundation, NASA grant NNX16AR67G (Fermi), and by Perimeter Institute for Theoretical Physics. Research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development Canada and by the Province of Ontario through the Ministry of Research, Innovation and Science. Computational resources were provided by XSEDE/TACC under grant TG-PHY100053, TG-MCA99S008 and the Orbital cluster at Princeton University.
Publisher Copyright:
© 2016 IOP Publishing Ltd.
PY - 2016/12/1
Y1 - 2016/12/1
N2 - We continue our investigations of the development and importance of the one-arm spiral instability in long-lived hypermassive neutron stars (HMNSs) formed in dynamical capture binary neutron star mergers. Employing hydrodynamic simulations in full general relativity, we find that the one-arm instability is generic in that it can develop in HMNSs within a few tens of milliseconds after merger for all equations of state in our survey. We find that mergers with stiffer equations of state tend to produce HMNSs with stronger m = 2 azimuthal mode density deformations, and weaker m = 1 components, relative to softer equations of state. We also find that for equations of state that can give rise to double-core HMNSs, large m = 1 density modes can already be present due to asymmetries in the two cores. This results in the generation of l = 2, m = 1 gravitational wave modes even before the dominance of a one-arm mode that ultimately arises following merger of the two cores. Our results further suggest that stiffer equations of state give rise to HMNSs generating lower m = 1 gravitational wave frequencies. Thus, if gravitational waves from the one-arm instability are detected, they could in principle constrain the neutron star equation of state. We estimate that, depending on the equation of state, the one-arm mode could potentially be detectable by second generation gravitational wave detectors at ∼10 Mpc and by third generation ones at ∼100 Mpc. Finally, we provide estimates of the properties of dynamical ejecta, as well as the accompanying kilonovae signatures.
AB - We continue our investigations of the development and importance of the one-arm spiral instability in long-lived hypermassive neutron stars (HMNSs) formed in dynamical capture binary neutron star mergers. Employing hydrodynamic simulations in full general relativity, we find that the one-arm instability is generic in that it can develop in HMNSs within a few tens of milliseconds after merger for all equations of state in our survey. We find that mergers with stiffer equations of state tend to produce HMNSs with stronger m = 2 azimuthal mode density deformations, and weaker m = 1 components, relative to softer equations of state. We also find that for equations of state that can give rise to double-core HMNSs, large m = 1 density modes can already be present due to asymmetries in the two cores. This results in the generation of l = 2, m = 1 gravitational wave modes even before the dominance of a one-arm mode that ultimately arises following merger of the two cores. Our results further suggest that stiffer equations of state give rise to HMNSs generating lower m = 1 gravitational wave frequencies. Thus, if gravitational waves from the one-arm instability are detected, they could in principle constrain the neutron star equation of state. We estimate that, depending on the equation of state, the one-arm mode could potentially be detectable by second generation gravitational wave detectors at ∼10 Mpc and by third generation ones at ∼100 Mpc. Finally, we provide estimates of the properties of dynamical ejecta, as well as the accompanying kilonovae signatures.
KW - binary neutron star mergers
KW - gravitational waves
KW - hypermassive neutron stars
KW - kilonovae
KW - neutron star equation of state
KW - one-arm instability
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U2 - 10.1088/0264-9381/33/24/244004
DO - 10.1088/0264-9381/33/24/244004
M3 - Article
AN - SCOPUS:85003968545
SN - 0264-9381
VL - 33
JO - Classical and Quantum Gravity
JF - Classical and Quantum Gravity
IS - 24
M1 - 244004
ER -