2017/02/15 by Liang Dai, Tejaswi Venumadhav, Dai, Liang +1 · 6 citations
Physics and Astronomy · #Pulsars and Gravitational Waves Research #Adaptive optics and wavefront sensing #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.1702.04724
Strong lensing by intervening galaxies can produce multiple images of gravitational waves from sources at cosmological distances. These images acquire additional phase-shifts as the over-focused wavefront passes through itself along the line of sight. Time domain waveforms of Type-II images (associated with saddle points of the time delay) exhibit a non-trivial distortion from the unlensed waveforms. This phenomenon is in addition to the usual frequency-independent magnification, and happens even in the geometric limit where the wavelength is much shorter than the deflector's gravitational length scale. Similarly, Type-III images preserve the original waveform's shape but exhibit a sign flip. We show that for non-precessing binaries undergoing circular inspiral and merger, these distortions are equivalent to rotating the line of sight about the normal to the orbital plane by 45^∘ (Type II) and 90^∘ (Type III). This effect will enable us to distinguish between the different topological types among a set of multiple images, and give us valuable insight into the lens model. Furthermore, we show that for eccentric binaries, the waveform of a Type-II image is distorted in a manner that is inequivalent to a change of the source's orbital parameters.