Broadband linear polarimetry of exoplanet Upsilon Andromedae b: Constraints on the orbital and physical parameters

Abstract Context . Modern polarimeters enable precise measurements of exoplanetary systems, providing valuable constraints on orbital geometry and atmospheric scattering properties. Aims . We aim to investigate the orbital parameters of the non-transiting Jupiter-like exoplanet ʋ And b, which orbits close to its host star, using polarized scattered light observed with the DiPol-2 polarimeter on a 60 cm telescope. Methods . Over nearly three years, we collected high-precision polarimetric data of the ʋ And system. Using Lomb-Scargle periodograms, we identified variability close to the planetary orbital phase and modeled the signal with the Rayleigh-Lambert approximation. Results . A weak polarimetric signal at half the orbital period of ʋ And b was detected. The V -band MCMC fits yielded an orbital inclination of , an argument of periastron , a longitude of ascending node , and a geometric albedo of . Although uncertainties remain large, the inclination result agrees with earlier estimates, supporting a low-inclination, non-transiting geometry. Conclusions . While the detection is not definitive, these results demonstrate the capability of high-precision polarimetry to probe the orbital parameters of non-transiting exoplanets. Further observations with larger telescopes and improved sensitivity will be required to refine the constraints on the orbital parameters.