4,326 research outputs found
Magnetic-distortion-induced ellipticity and gravitational wave radiation of neutron stars: millisecond magnetars in short GRBs, Galactic pulsars, and magnetars
Neutron stars may sustain a non-axisymmetric deformation due to magnetic
distortion and are potential sources of continuous gravitational waves (GWs)
for ground-based interferometric detectors. With decades of searches using
available GW detectors, no evidence of a GW signal from any pulsar has been
observed. Progressively stringent upper limits of ellipticity have been placed
on Galactic pulsars. In this work, we use the ellipticity inferred from the
putative millisecond magnetars in short gamma-ray bursts (SGRBs) to estimate
their detectability by current and future GW detectors. For ms
magnetars inferred from the SGRB data, the detection horizon is Mpc
and Mpc for advanced LIGO (aLIGO) and Einstein Telescope (ET),
respectively. Using the ellipticity of SGRB millisecond magnetars as
calibration, we estimate the ellipticity and gravitational wave strain of
Galactic pulsars and magnetars assuming that the ellipticity is
magnetic-distortion-induced. We find that the results are consistent with the
null detection results of Galactic pulsars and magnetars with the aLIGO O1. We
further predict that the GW signals from these pulsars/magnetars may not be
detectable by the currently designed aLIGO detector. The ET detector may be
able to detect some relatively low frequency signals ( Hz) from some of
these pulsars. Limited by its design sensitivity, the eLISA detector seems not
suitable for detecting the signals from Galactic pulsars and magnetars.Comment: Accepted for publication in Ap
Possible High-Energy Neutrino and Photon Signals from Gravitational Wave Bursts due to Double Neutron Star Mergers
As the technology of gravitational-wave and neutrino detectors becomes
increasingly mature, a multi-messenger era of astronomy is ushered in. Advanced
gravitational wave detectors are close to making a ground-breaking discovery of
gravitational wave bursts (GWBs) associated with mergers of double neutron
stars (NS-NS). It is essential to study the possible electromagnetic (EM) and
neutrino emission counterparts of these GWBs. Recent observations and numerical
simulations suggest that at least a fraction of NS-NS mergers may leave behind
a massive millisecond magnetar as the merger product. Here we show that protons
accelerated in the forward shock powered by a magnetar wind pushing the ejecta
launched during the merger process would interact with photons generated in the
dissipating magnetar wind and emit high energy neutrinos and photons. We
estimate the typical energy and fluence of the neutrinos from such a scenario.
We find that PeV neutrinos could be emitted from the shock front as long
as the ejecta could be accelerated to a relativistic speed. The diffuse
neutrino flux from these events, even under the most optimistic scenarios, is
too low to account for the two events announced by the IceCube Collaboration,
but it is only slightly lower than the diffuse flux of GRBs, making it an
important candidate for the diffuse background of PeV neutrinos. The
neutron-pion decay of these events make them a moderate contributor to the
sub-TeV gamma-ray diffuse background.Comment: Accepted for publication in PRD, minor revisio
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