The RoboPol sample of optical polarimetric standards

Abstract

Optical polarimeters are typically calibrated using measurements of stars with known and stable polarization parameters. 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 used polarimetric standards 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 five years, we have been running a monitoring campaign of a sample of standard candidates comprised of 107 stars distributed across the northern sky. We analyzed the variability of the linear polarization of these stars, taking into account the non-Gaussian nature of fractional polarization measurements. For a subsample of nine stars, we also performed multiband polarization measurements. We created a new catalog of 65 stars (see Table 2) that are stable, have small uncertainties of measured polarimetric parameters, and can be used as calibrators of polarimeters at medium- and large-size telescopes.

References in corpus (12)

• 9286 Stars: An Agglomeration of Stellar Polarization Catalogs
• Placing Confidence Limits on Polarization Measurements
• Error Analysis for Dual-Beam Optical Linear Polarimetry
• The RoboPol Pipeline and Control System
• RoboPol: A four-channel optical imaging polarimeter
• RoboPol: AGN polarimetric monitoring data
• Linear spectropolarimetry of polarimetric standard stars with VLT/FORS2
• Local measurements of the mean interstellar polarization at high Galactic latitudes
• Optical linear polarization of 74 white dwarfs with the RoboPol polarimeter
• Mapping the Polarization of the Radio-Loud Ly$\alpha$ Nebula B3 J2330+3927
• A Decade of Linear and Circular Polarimetry with the POLISH2 Polarimeter
• Calibration of EFOSC2 broadband linear imaging polarimetry

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• Bright-Moon Sky as a Wide-Field Linear Polarimetric Flat Source for Calibration
• Polarization position angle standard stars: a reassessment of $\theta$ and its variability for seventeen stars based on a decade of observations
• The WALOP-North Instrument I: Optical Design, Filter Design, Calibration
• Long-term optical variability of high-mass X-ray binaries. III. Polarimetry
• Zero-polarization candidate regions for calibration of wide-field optical polarimeters
• Systems design, assembly, integration and lab testing of WALOP-South Polarimeter