2023PASJ...75..269T

We present BVRI polarimetric measurements of nine bright stars in a 15'-square region centered on Stock 19. Seven of them satisfy the Serkowski equation for star light polarization due to interstellar dust. This allowed us to estimate the degree of maximum polarization (p_max) and the wavelength of maximum polarization (λ_max). Along this line of sight, p_max ranges from 0.332% to 0.948%, and the average λ_max of 0.542 ± 0.018 μm yields a total-to-selective extinction ratio R_V = 3.04 ± 0.11. Four of the observed stars were previously listed as high-probability members of Stock 19. However, based on their Gaia distances, they are spread out along the line of sight and show a correlation between polarization and distance that is typical for the diffuse interstellar medium. The extinction, as obtained from dust maps, and the Planck 353 GHz polarization are low for this line of sight, additionally suggesting that these stars might not represent an actual cluster. The polarization parameters of three of the observed stars indicate the possible presence of an intrinsic polarization component, likely due to circumstellar material.