Simulating Gravitational Microlensing Events by TESS: Predictions on Statistics and Properties

Abstract

We study the statistics and properties of microlensing events that can be detected by the Transiting Exoplanet Survey Satellite (TESS) based on Monte Carlo simulations. We simulate potential microlensing events from a sample of TESS Candidate Target List (CTL) stars by assuming different observational time spans (or different numbers of sectors for each star) and a wide range of lens masses, i.e., M l ∈ [0.1 M ⊕, 2 M ⊙]. On average, the microlensing optical depth and the event rate for CTL stars are ≃0.2 × 10−9 and ΓTESS ≃ 0.6 × 10−9 star–1 day–1, respectively. The microlensing optical depth decreases with increasing CTL priority, whereas the efficiency for detecting their microlensing signals enhances with priority. Additionally, we simulate microlensing events from TESS Full Frame Image (FFI) stars extracted from the TESS-SPOC pipeline. The optical depth and event rate for these stars are on average ≃1–3 × 10−9, and ΓTESS ≃ 1–4 × 10−9 star–1 day–1, and their highest values occur for Sector 12. The total number of microlensing events for the CTL stars is N e,tot ∼ 0.03, whereas for the FFI stars the number of events per star during the 27.4 day observing windows is Nˆe,tot≃1.4×10−6 . Based on four criteria we extract the detectable microlensing events and evaluate the detection efficiencies. The highest efficiency for detecting microlensing events from the TESS data occurs for lens masses of log10[Ml(M⊙)]∈[−4.5 , −2.5], i.e., super-Earths to Jupiter-mass free floating planets. The detectable microlensing events from the TESS stars are significantly affected by both finite-source and parallax effects.