Abstract
We conduct force-free simulations of a single neutron star undergoing orbital motion in flat spacetime, mimicking the trajectory of the star about the center of mass on a compact binary system. Our attention is focused on the kinetic energy being extracted from the orbit by the acceleration of the magnetic dipole moment of the neutron star and, particularly, on how this energy gets distributed within its surrounding magnetosphere. A detailed study of the resulting magnetospheric configurations in our setting is presented, incorporating as well the effects due to neutron star spin and the misalignment of the magnetic and orbital axes. We find many features resembling those of pulsar magnetospheres for the orbiting neutron star---even in the absence of spin-of particular interest being the development of a spiral current sheet that extends beyond the light cylinder. Then, we use recent advances in pulsar theory to estimate electromagnetic emissions produced at the reconnection regions of such current sheets.
Highlights
A new era of multimessenger astronomy has started with the detection of gravitational waves (GW) from a binary neutron star merger (GW170817) by advanced LIGO/advanced Virgo [1,2], followed by broadband electromagnetic (EM) observations [3]
We find many features resembling those of pulsar magnetospheres for the orbiting neutron star—even in the absence of spin-of particular interest being the development of a spiral current sheet that extends beyond the light cylinder
Our interest in this work is centered on the last few orbits of a neutron star (NS) on a compact binary system, until the orbit reaches an innermost stable circular orbit or the NS gets tidally disrupted
Summary
A new era of multimessenger astronomy has started with the detection of gravitational waves (GW) from a binary neutron star merger (GW170817) by advanced LIGO/advanced Virgo [1,2], followed by broadband electromagnetic (EM) observations [3]. Binary systems involving a neutron star (NS) are the most likely sources for such simultaneous detections of GW and EM signals In this context, EM emissions from the relatively cleaner environment preceding the merger could provide crucial information about the merger process, sky localization of the source, and the physical parameters of the system, which cannot be accurately obtained only by the gravitational wave observation. The source for the precursor EM counterparts comes fundamentally from the orbital and rotational energy of the binary and its individual constituents. This kinetic energy is first electromagnetically extracted from each compact object, by means of the surrounding plasma, and later reprocessed
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