Simulations of triple microlensing events I: detectability of a scaled Sun–Jupiter–Saturn system

Up to date, only 13 firmly established triple microlensing events have been discovered, so the occurrence rates of microlensing two-planet systems and planets in binary systems are still uncertain. With the upcoming space-based microlensing surveys, hundreds of triple microlensing events will be detected. To provide clues for future observations and statistical analyses, we initiate a project to investigate the detectability of triple-lens systems with different configurations and observational set-ups. As the first step, in this work we develop the simulation software and investigate the detectability of a scaled Sun–Jupiter–Saturn system with the recently proposed telescope for microlensing observations on the ‘Earth 2.0 (ET)’ satellite. With the same Δχ ² thresholds of detecting a single planet and two planets, we find that the detectability of the scaled Sun-Jupiter-Saturn analogue is about 1 per cent and the presence of the Jovian planet suppresses the detectability of the Saturn-like planet by ∼13 per cent regardless of the adopted detection Δχ ² threshold. This suppression probability could be at the same level as the Poisson noise of future space-based statistical samples of triple-lenses, so it is inappropriate to treat each planet separately during detection efficiency calculations.