Vivek Chaurasia (Stockholm University) will present "BNS Mergers: Effect of Spin Orientation"

Europe/Stockholm
Description

Join: https://stockholmuniversity.zoom.us/j/446165416

 


In this talk I will review the results of arXiv: 2003.11901 which is a
continuation of our study of the binary neutron star parameter space
by investigating the effect of the spin orientation on the dynamics,
gravitational wave emission, and mass ejection during the binary
neutron star coalescence. For this we perform fully consistent (3+1) D
numerical relativity simulations for various precessing systems.
Although pulsar observations of BNS systems suggest that most NSs have
small spins this conclusion is based on a small selected set of
observed binaries. Similar to the uncertainty in the spin magnitude,
the orientation of spins in BNS systems is also highly uncertain and
unknown. Misaligned spins can be caused by the supernova explosions of
the progenitor stars.  A possible realignment of the spin with the
orbital angular momentum due to accretion is only possible for the
more massive NS, but not for the secondary star. In addition, for BNS
systems formed due to dynamical capture, there is no reason to have
aligned spins at all. We find that due  to  the  particular  choice
of  the  setups, five  configurations  show  precession  effects,
from  which  two  show  a  precession  (‘wobbling’)  of  the orbital
plane,  while three show a ‘bobbing’ motion,  i.e.,  the orbital
angular momentum does not precess, while the orbital plane moves along
the orbital angular momentum axis.  Considering the ejection of mass,
we find that precessing systems can have an anisotropic mass ejection,
which could lead to a final remnant kick of about ∼40km/s for the
studied systems. Furthermore, for the chosen configurations,
anti-aligned spins lead to larger mass ejecta than aligned spins, so
that brighter electromagnetic counterparts could be expected for these
configurations.  Finally, we compare our simulations with the
precessing, tidal waveform approximant and find good agreement between
the approximant and our numerical relativity simulations.

 

 

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