Optical polarimetry of blazars detected at TeV γ-rays

Abstract

We present results from an optical polarimetric study of blazars that have been detected at very high-energy (VHE) -γ rays. We look for short time-scale fluctuations (i.e., microvariability) either/both in their polarisation percent or position angle in the B and R optical bands. Spurious effects introduced by light contamination from the host galaxy, especially due to seeing FWHM variations, are quantitatively analysed.