Vol. 635
6. Interstellar and circumstellar matter

High-precision polarimetry of nearby stars (d<50 pc)

Understanding the magnetic field of the interstellar medium (ISM) in the vicinity of the Sun is a supremely challenging task, requiring ultra-high-precision polarimetric measurements of as large a sample of stars with known distances as possible. This benchmark study uses a sample of 361 bright F and G stars to obtain UBV photometric polarimetry to a remarkable level, 10^(-5). A subset of the sample of nonactive stars shows some marginal evidence of variability, which is probably intrinsic. A key result is the delineation of large angular-scale coherent filamentary structures, which are detected in the position angle maps that correspond to features known from the local ISM. In particular, there is a signature of the Interstellar Boundary EXplorer (IBEX) ribbon that is connected with the local IS magnetic field, which was modified by the heliosphere. The study also shows correlations between high-latitude large arc structures revealed by samples at distances from 100 to 500 pc and those closer than 50 pc.