Science with a large field-of-view polarization survey: The Large Array Survey Telescope Polarization Node (LAST-P)

Abstract

Optical polarimetry provides information on the geometry of the emitting region, the magnetic field configuration and the properties of dust in astrophysical sources. Current state-of-the-art instruments typically have a small field of view (FoV), which poses a challenge for conducting wide surveys. We propose the construction of the Large Array Survey Telescope Polarization Node (LAST-P), a wide-field array of optical polarimeters. LAST-P is designed for high-cadence ($\lesssim 1$ day) polarization monitoring of numerous astrophysical transients, such as the early phases of gamma-ray bursts, supernovae, and novae. Furthermore, LAST-P will facilitate the creation of extensive polarization catalogs for X-ray binaries and white dwarfs, alongside a large FoV study of the interstellar medium. In survey mode, LAST-P will cover a FoV of 88.8 deg$^2$. With a 15 x 1-minute exposure, the instrument will be capable of measuring polarization of sources as faint as Gaia Bp-magnitude $\sim$20.9. The precision on the linear polarization degree (PD) will reach 0.7\%, 1.5\%, and 3.5\% for sources with magnitudes 17, 18, and 19, respectively, for a seeing of 2.7 arcsec, air mass of about 1 for observations in dark locations. We propose three distinct non-simultaneous survey strategies, among them an active galactic nuclei (AGN) strategy for long-term monitoring of $\sim$200 AGN with $<$1-day cadence. In this paper, we present the predicted sensitivity of the instrument and outline the various science cases it is designed to explore.