Broadband Linear Polarimetry of Exoplanet Upsilon Andromedae b: Constraints on the Orbital and Physical Parameters

Recent advancements in astronomical polarimetry have enabled the detection and characterization of exoplanets, providing insights into their orbital parameters, atmospheric composition, and reflective properties. By combining polarimetric studies with spectroscopy and photometry, a comprehensive understanding of exoplanets, including non-transiting hot Jupiters like υ And b, can be achieved. The polarimetric observations of the υ And star system were conducted over a period of nearly three years, capturing data at different orbital phases of υ And b. We used T60 telescope in combination with high-precision DiPol-2 polarimeter, which provided an exceptionally high accuracy. To identify periodic signals in our unevenly sampled polarimetric data, we employed the Lomb-Scargle periodogram method. Our findings revealed a polarimetric signal precisely at half of the known orbital period of υ And b, as expected from the polarimetric data of an exoplanet. By applying the Rayleigh-Lambert scattering model, we derived constraints on the exoplanet’s orbital parameters, including inclination angle, longitude of periastron, and longitude of the ascending node. Combining these results with previous spectroscopic studies, we determined the planetary mass, mean density, and surface gravity of υ And b. Additionally, our analysis of Transiting Exoplanet Survey Satellite (TESS) photometric data for υ And provided further evidence suggesting the presence of starspots, which likely affected the observed polarimetric signal of the exoplanets. Consequently, accurately quantifying the scattering atmosphere radius and planetary albedo of υ And b proved to be elusive. In conclusion, high-precision polarimetry serves as a powerful tool for studying exoplanets, allowing for the deduction of their orbital parameters and atmospheric properties. This study highlights the significant potential of astronomical polarimetry in characterizing various types of exoplanets. By incorporating multiple observational techniques, we can enhance our understanding of the complex nature of explanatory systems.