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Thursday, December 09, 2021
1:00 PM - 2:00 PM

LIGO Seminar

Gravitational Saves from a Newly Born Hyper-Accreting Millisecond Magnetar

Speaker: Ankan Sur

Gravitational Waves from a Newly Born Hyper-Accreting Millisecond Magnetar

Millisecond Magnetars are formed either after core-collapse supernovae or as a remnants of binary neutron star mergers. We develop a toy model of a newly born millisecond magnetar and study the spin-evolution and gravitational-wave luminosity. In both cases we consider the effect of fallback accretion, and consider the evolution of the system due to the different torques acting on the star, namely the spin-up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational wave emission linked to the formation of a ‘mountain' on the accretion poles. We find that a magnetar formed after the collapse of a massive star can accrete up to 1 M , and survive on the order of 50 s before collapsing into a black hole. The gravitational wave strain, for an object located at 1 Mpc, is h_c \sim 10^{-23} at kHz frequencies, making this a potential target for next generation ground-based detectors. A magnetar formed after a binary neutron star merger, on the other hand, accretes at the most 0.2 MSun, and emits gravitational waves with a lower maximum strain , but also survives for much longer times, and may possibly be associated with the X-ray plateau observed in the light curve of a number of short gamma-ray burst.

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