Exploring the faint limit of the ESA Plato space mission
Year: 2026
Type: article
Abstract: Context. The search for supermassive black hole (SMBH) binaries has, in recent years, seen the dawn of exploration with several hundred candidates claimed from photometric and spectroscopic surveys monitoring active galactic nuclei (AGNs). While only a select number persist to date, the advent of upcoming high-precision wide-field photometric missions motivates continuing the pursuit of confirming SMBH binaries (SMBHBs) in the optical. Aims. We explore the possibility of using the Plato space mission of ESA to detect photometric signatures of SMBH binarity. Since many accretion-related signatures are not uniquely related to binaries, nor easily disentangled, the distinct photometric signature, strict occurrence in phase, and duration of a gravitational self-lensing flare (SLF) can strongly reduce such signal confusion. Motivated by the Kepler observation of Spikey, the best known SLF candidate to date, this work aims to benchmark the scientific outcome if Plato were to observe Spikey-like objects via its Guest Observer programme. Methods. Starting from the Gaia database, we assembled a catalogue of 12 226 bright ( G < 19) high-probability quasars (or QSOs) for the two pointing fields of Plato ’s nominal mission. This Plato quasar catalogue will be pivotal for future follow-up observations of larger photometric searches such as the Vera Rubin LSST survey. We used the Plato camera simulator, PlatoSim , to realistically explore the noise budget in Plato ’s faint limit, while generating mock light curves to benchmark Plato ’s ability to recover signatures of SMBH binarity. These signatures were secured using nested sampling for robust probabilistic modelling. Results. We show that, although not originally designed for this purpose, Plato is capable of detecting Spikey-like SMBHB candidates through their relativistic photometric signatures using Bayesian inference and evidence. Plato will, in particular, be able to confirm or rule out Spikey and Spikey-like objects with a limiting magnitude of G ≤ 18. Conclusions. With a minimum 2 yr baseline per pointing field, we show that Plato could not only play an essential role in future SMBHB research, but it may be an integral part of the observational fleet of continuous high-precision facilities monitoring SMBHB candidates in the near future.
Source: Astronomy and Astrophysics
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7214923790