High-precision polarimetry of nearby stars (d<50 pc) Mapping the
  interstellar dust and magnetic field inside the Local Bubble
  We investigate the linear polarization produced by interstellar dust aligned
by the magnetic field in the solar neighborhood (d< 50 pc). We also look for
intrinsic effects from circumstellar processes, specifically in terms of
polarization variability and wavelength dependence. We aim to detect and map
dust clouds which give rise to statistically significant amounts of
polarization of the starlight passing through the cloud, and to determine the
interstellar magnetic field direction from the position angle of the observed
polarization. High-precision broad-band (BVR) polarization observations are
made of 361 stars in spectral classes F to G, in the magnitude range 4-9, with
detection sensitivity at the level of or better than 10E-5 (0.001 %).
Statistically significant (>3 sigma) polarization is found in 115 stars, and >
2 sigma detection in 178 stars, out of the total sample of 361 stars.
Polarization maps based on these data show filament-like patterns of
polarization position angles which are related to both the heliosphere
geometry, the kinematics of nearby clouds, and the Interstellar Boundary
EXplorer (IBEX) ribbon magnetic field. From long-term multiple observations, a
number (18) of stars show evidence of intrinsic variability at the 10E-5 level.
This can be attributed to circumstellar effects (e.g., debris disks and
chromospheric activity). The star HD 101805 shows a peculiar wavelength
dependence, indicating size distribution of scattering particles different from
that of a typical interstellar medium.
