Polarization and photometric observations of the gamma-ray blazar PG?1553+113

摘要

We present the results of an observational photo-polarimetry campaign of the blazar PG?1553+113 at optical wavelengths. The blazar was recently detected at very high energies (>100?GeV) by the HESS and MAGIC γ-ray Cherenkov telescopes. Our?high-temporal resolution data show significant variations in the linear polarization percentage and position angle at inter-night time-scales, while at shorter (intra-night) time-scales both parameters varied less significantly, if?at?all. Changes in the polarization angle seem to be common in γ-ray emitting blazars. Simultaneous differential photometry (through the?B and R?bands) shows no significant variability in the total optical flux. We provide?B and R?magnitudes, along with a finding chart, for?a?set of field stars suitable for differential photometry.