RoboPol sample of optical polarimetric standards

However, there is a lack of such stars available across the sky. Many of the currently available standards are not suitable for medium and large telescopes due to their high brightness.

Moreover, as we find, some of the polarimetric standards used are in fact variable or have polarization parameters that differ from their cataloged values. Our goal is to establish a sample of stable standards suitable for calibrating linear optical polarimeters with an accuracy down to 10^-3^ in fractional polarization. For 4yr, we have been running a monitoring campaign of a sample of standard candidates comprised of 107 stars distributed across the northern sky.