Eclipses of continuous gravitational waves as a probe of stellar structure

Abstract

Although gravitational waves only interact weakly with matter, their propagation is affected by a gravitational potential. If a gravitational wave source is eclipsed by a star, measuring these perturbations provides a way to directly measure the distribution of mass throughout the stellar interior. We compute the expected Shapiro time delay, amplification and deflection during an eclipse, and show how this can be used to infer the mass distribution of the eclipsing body. We identify continuous gravitational waves from neutron stars as the best candidates to detect this effect. When the Sun eclipses a far-away source, depending on the depth of the eclipse the timedelay can change by up to ∼ 0.034 ms, the gravitational-wave strain amplitude can increase by ∼ 4%, and the apparent position of the source in the sky can vary by 4 . Accreting neutron stars with Roche-lobe filling companion stars have a high probability of exhibiting eclipses, producing similar time delays but undetectable changes in amplitude and sky location. Even for the most rapidly rotating neutron stars, this time delay only corresponds to a few percent of the phase of the gravitational wave, making it an extremely challenging measurement. However, if sources of continuous gravitational waves exist just below the limit of detection of current observatories, nextgeneration instruments will be able to observe them with enough precision to measure the signal of an eclipsing star. Detecting this effect would provide a new direct probe to the interior of stars, complementing asteroseismology and the detection of solar neutrinos.

Solar Diffraction of LIGO-Band Gravitational Waves

“…The same physics was exploited to probe diffuse NFW dark matter profile with GWs [11]. Other ways to measure the lens mass profile include the well-known weak lensing by a galaxy and the eclipse by a lens star [27].…”

Wave-optical Effects in the Microlensing of Continuous Gravitational Waves by Star Clusters

“…In this respect, Liao et al (2019) have demonstrated that diffraction and interference effects may, albeit rarely, show up in continuous GW signals, and that the amplitude and phase modulations arising due to lensing can non-negligibly affect parameter estimation (see also de Paolis et al 2001;Diego et al 2019;Marchant et al 2020;Meena & Bagla 2020;Mishra et al 2021). However, these authors concentrated on the case of a single point-mass lens, where a closed-form expression for the lensing flux is available (Nakamura & Deguchi 1999), thereby allowing for analytically tractable computations.…”

Lensed or not lensed: Determining lensing magnifications for binary neutron star mergers from a single detection

“…A number of possibilities to identify a lensed GW signal have been proposed. One can look for signatures of multiple images or microlensing within GW data [23,29,[36][37][38][39][40]. Alternatively, one could search for a population of apparently high-mass binary events produced by lensing magnification [19,26,41].…”