Lensing rates of gravitational wave signals displaying beat patterns detectable by DECIGO and B-DECIGO

Abstract

The coherent nature of gravitational wave emanating from a compact binary system makes it possible to detect some interference patterns in two (or more) signals registered simultaneously by the detector. Gravitational lensing effect can be used to bend trajectories of gravitational waves, which might reach the detector at the same time. Once this happens, a beat pattern may form, and can be used to obtain the luminosity distance of the source, the lens mass, and cosmological parameters such as the Hubble constant. Crucial question is how many such kind of events could be detected. In this work, we study this issue for the future space-borne detectors: DECIGO and its downscale version, B-DECIGO. It is found out that there can be a few tens to a few hundreds of lensed gravitational wave events with the beat pattern observed by DECIGO and B-DECIGO per year , depending on the evolution scenario leading to the formation of double compact objects. In particular, black hole-black hole binaries are dominating population of lensed sources in which beat patterns may reveal. However, DECIGO could also register a considerable amount of lensed signals from binary neutron stars, which might be accompanied by electromagnetic counterparts. Our results suggest that, in the future, lensed gravitational wave signal with the beat pattern could play an important role in cosmology and astrophysics.

A Higher Probability of Detecting Lensed Supermassive Black Hole Binaries by LISA

“…In this case, wave diffraction would modify the amplitude and phase of the GWs, producing a characteristic "beating pattern" in the frequency domain of the waveform (Takahashi & Nakamura 2003). In addition, the waveoptics effect could also smear the plane of GW polarization (Cusin & Lagos 2020) and produce beat patterns in the time-domain waveform (Yamamoto 2005;Hou et al 2020). These effects, in principle, could allow LIGO/Virgo to detect massive stars, IMBHs, and the dense cores of globular clusters and dark-matter (DM) halos (Moylan et al 2008;Cao et al 2014;Takahashi 2017;Christian et al 2018;Dai et al 2018;Diego et al 2019;Jung & Shin 2019;Liao et al 2019;Meena & Bagla 2020;Oguri & Takahashi 2020).…”