Gravitational Wave Detection with Photometric Surveys

TL;DR

This paper proposes a novel method for gravitational wave detection using photometric survey astrometry, offering a complementary frequency range to existing detectors and exploring its potential with the Roman Space Telescope.

Contribution

It introduces a new GW detection approach based on astrometric measurements from photometric surveys, expanding the observational window for supermassive black hole binaries.

Findings

Roman EML survey can probe GW frequencies from 7.7e-8 Hz to 5.6e-4 Hz.

Detection of individual GWs requires improved astrometric accuracy and sensitivity.

Binaries with chirp mass >10^8.3 M_sun at 100 Mpc could be detected with current capabilities.

Abstract

Gravitational wave (GW) detections have enriched our understanding of the universe. To date, all single-source GW events were found by interferometer-type detectors. We study a detection method using astrometric solutions from photometric surveys and demonstrate that it offers a highly flexible frequency range, uniquely complementing existing detection methods. From repeated point-source astrometric measurements, we may extract GW-induced deflections and infer wave parameters. This method can be applied to any photometric surveys measuring relative astrometry. We show that high-cadence observations of the galactic bulge, such as offered by the Roman Space Telescope's Exoplanet MicroLensing (EML) survey, can be a potent GW probe with complementary frequency range to Gaia, pulsar timing arrays (PTAs), and the Laser Interferometer Space Antenna (LISA). We calculate that the Roman EML survey is sensitive to GWs with frequencies ranging from $7.7\times10^{-8}$Hz to $5.6\times10^{-4}$Hz, which opens up a unique GW observing window for supermassive black hole binaries and their waveform evolution. While the detection threshold assuming the currently expected performance proves too high for detecting individual GWs in light of the expected supermassive black hole binary population distribution, we show that binaries with chirp mass $M_c>10^{8.3}~M_\odot$ out to 100 Mpc can be detected if the telescope is able to achieve an astrometric accuracy of 0.11 mas. To confidently detect binaries with $M_c>10^{7}~M_\odot$ out to 50 Mpc, a factor of 100 sensitivity improvement is required. We propose several improvement strategies, including recovering the mean astrometric deflection and increasing astrometric accuracy, number of observed stars, field-of-view size, and observational cadence. We discuss how other existing and planned photometric surveys could contribute to detecting GWs via astrometry.