Fig. 5: Aperture polarimetry of 2I/Borisov in the RF filter.
From: Unusual polarimetric properties for interstellar comet 2I/Borisov
Blue filled circles refer to Pr and red filled squares refer to U/I. The dotted black solid lines show the values adopted in Table 1. Panel a refers to data obtained on 2019-12-25, when polarisation was directed along the direction perpendicular to the scattering plane. Panel b refers to observations obtained on 2020-03-20, when polarisation was directed along the scattering plane; for these observations, CCD readout was rebinned 2 × 2, which explains the less refined sampling of the growth curve (compared to a). Reduced Stokes parameters are computed in circles of radius given in the abscissa. The Wollaston strip is 22″ wide, therefore aperture radius cannot be larger than 11″. Practically, the aperture limit is determined by the contamination of background stars (see Fig. 3). Error bars are calculated as explained in Methods subsection Polarimetry.
