Monitoring the Sky with the Prototype All-Sky Imager on the LWA1

TL;DR

The paper describes the PASI system on LWA1 that creates all-sky images at low frequencies, enabling new transient searches and setting limits on transient rates and energies.

Contribution

Introduction of the PASI backend correlator and imager for LWA1, providing near real-time all-sky imaging at low frequencies and new transient search capabilities.

Findings

Over 13,000 hours of all-sky images recorded

Set upper limits on transient rate densities at multiple frequencies

Established pulse energy density limits for transient detection

Abstract

We present a description of the Prototype All-Sky Imager (PASI), a backend correlator and imager of the first station of the Long Wavelength Array (LWA1). PASI cross-correlates a live stream of 260 dual-polarization dipole antennas of the LWA1, creates all-sky images, and uploads them to the LWA-TV website in near real-time. PASI has recorded over 13,000 hours of all-sky images at frequencies between 10 and 88 MHz creating opportunities for new research and discoveries. We also report rate density and pulse energy density limits on transients at 38, 52, and 74 MHz, for pulse widths of 5 s. We limit transients at those frequencies with pulse energy densities of $>2.7\times 10^{-23}$, $>1.1\times 10^{-23}$, and $>2.8\times 10^{-23}$ J m$^{-2}$ Hz$^{-1}$ to have rate densities $<1.2\times10^{-4}$, $<5.6\times10^{-4}$, and $<7.2\times10^{-4}$ yr$^{-1}$ deg$^{-2}$