Magnetic-distortion-induced Ellipticity and Gravitational Wave Radiation of Neutron Stars: Millisecond Magnetars in Short GRBs, Galactic Pulsars, and Magnetars

Abstract

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 ∼ 1 ms magnetars inferred from the SGRB data, the detection horizon is ∼ 30 Mpc and ∼ 600 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-distortioninduced. 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 (< 50 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.

The Allowed Parameter Space of a Long-lived Neutron Star as the Merger Remnant of GW170817

“…Recently, an ellipticity of the order ǫ ∼ 0.005 for a rapidly spinning (millisecond), strongly magnetized (10 15 G), supramassive NS has been inferred from the statistical observational properties of Swift SGRBs (Gao et al 2016). With such a normalization, the relation between ǫ and B p can be then calibrated (Gao et al 2017c). According to this relation, the above quantitative constraints for ǫ = 10 −3 would be no longer relevant, since B p is required to be in the level of 10 15 G in order to achieve ǫ = 10 −3 .…”

Gravitational waves from fast-spinning white dwarfs

“…Different possibilities of generation of continuous GWs have already been proposed (see e.g., Bonazzola & Gourgoulhon 1996;De Araujo et al 2016a,b;Mukhopadhyay et al 2017;De Araujo et al 2017;Gao et al 2017;Franzon & Schramm 2017;Pereira et al 2018;De Araujo et al 2019, and references therein). More recently, Kalita & Mukhopadhyay (2019) show that continuous GWs can be emitted from rotating magnetized WDs and will possibly be detected by the upcoming GW detectors such as LISA, DECIGO and BBO.…”

Search for the signatures of a new-born black hole from the collapse of a supra-massive millisecond magnetar in short GRB light curves

“…However, considering the small fall-back mass combined with accretion disc heating effects, the influence on the spin period is not important . In addition, the post-merger magnetar may undergo important gravitational wave (GW) radiation (e.g., Zhang & Mészáros 2001;Corsi & Mészáros 2009;Fan, Wu & Wei 2013;Dall'Osso et al 2015;Doneva, Kokkotas & Pnigouras 2015;Lasky & Glampedakis 2016;Gao, Cao & Zhang 2017), during which a significant spin energy is taken away by GWs. This affects the magnetar spin-down and the collapse time (Gao, Zhang & Lü 2016).…”