Abstract :
Massive black hole binaries (MBHBs) are expected to be among the
loudest gravitational wave sources detectable by pulsar timing arrays and space-borne interferometers. If accreting, MBHBs at sub-parsec
separations (<0.01 pc) can be identified through periodic variability in their light curves. The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), with its unprecedented wide-sky coverage, multi-band photometry, and high-cadence observations, will allow the detection of a large number of periodic MBHB candidates, which could then be validated through independent methods. Current periodicity detection methods, though, are largely optimised for quasi-sinusoidal signals, whereas the predicted light curves from MBHBs present a much richer phenomenology. In this talk, I will present a periodicity detection method based on Gaussian processes that flexibly models periodic variability independently of its specific shape. I will then introduce a spectroscopic test to distinguish photometrically selected MBHB candidates from single massive black holes with quasi-periodic continuum variability, using the response of the broad-line region (BLR).
