Astrometric signatures of stars with TESS planet candidates: close companions and false alarms

The quest to discover exoplanets, planets orbiting stars beyond our solar system, has been one of the most thrilling endeavors in contemporary astronomy. As astronomers employ advanced techniques and technologies to identify these distant worlds, the challenges posed by false positives have become a central focus of investigation. False positives in exoplanet detection, while presenting a formidable obstacle, also offer valuable insights into refining our methods and ensuring the accuracy of future discoveries. This master thesis investigates the astrometric signatures associated with stars hosting planet candidates detected by the Transiting Exoplanet Survey Satellite (TESS). The study encompasses a brief description of the historical context of exoplanet detection, detection techniques such as radial velocity, transit, and astrometry, and an introduction to the Gaia and TESS space missions. Emphasis is placed on addressing the potential for false positives in exoplanet identification. The research employs a comparative approach by cross-matching TESS catalogs with the recently released Gaia DR3 catalog and the Gaia-Hipparcos Proper Motion anomaly (PMa) catalog by Kervella et al. (2022). The properties of the candidate transiting exoplanets found by TESS, included in the so-called TESS Objects of Interest (TOI) catalog, are analyzed by using the Gaia DR3 catalog, and in particular, the information included in the Non-Single Star Catalogue (NSS) that is part of the Gaia release. The PMa catalog is introduced as a crucial component for evaluating proper motion anomalies. The heart of the study involves a detailed analysis of TOIs, by using the tables obtained by cross-matching the TOIs catalog with the NSS catalog (TOI-NSS) and with the Kervella’s catalog (TOI-PMa) The examination aims to uncover astrometric patterns and anomalies associated with the stellar hosts of TESS planet candidates. Notable cases, including TOI 503.01, TOI 1338.01, TOI 503.01 (HATS-26 b), WASP-2 b, TOI 148.01, TOI-185.01 (WASP-18 b), TOI 2543.01, TOI 144.01, TOI 179.01, TOI 200.01 (DS Tuc Ab), TOI 4399.01, and TOI 5394.01, are singled out for detailed scrutiny. The research contributes to the refinement of exoplanet catalogs by offering insights into the astrometric signatures of stars hosting TESS planet candidates. The comparative analysis with Gaia DR3 and proper motion anomalies enhances our understanding of the complexities within stellar systems observed by TESS, providing a foundation for future investigations in the dynamic field of exoplanetary science.