Stellar Activity Effects on Detection and Characterization of Exoplanets Utilizing TESS Data

Abstract

The current article explores the influence of stellar activity, specifically starspots and stellar flares, on the detection and characterization of exoplanets in TESS data. Stellar activity indicators (photometric modulation amplitude, flare frequency) were determined for 50 active G and K‑type stars. Significant positive correlations were found between stellar photometric variability and both the false‑alarm probability (p < 0.01) and the uncertainty of the measured planetary radius (R² = 0.76). Applying Gaussian process regression, a newly developed detrending algorithm for stellar activity indicators reduces the false‑positive rate by approximately 40% (from 18.6% to 11.2% in our sample) and improves the accuracy of planetary radius estimates by approximately 30% (reducing the mean relative uncertainty from 22.4% to 15.7% for injected Earth‑sized planets). Thus, accounting for stellar activity is essential for trustworthy exoplanet discovery and characterization.