AARTFAAC Flux Density Calibration and Northern Hemisphere Catalogue at 60 MHz

TL;DR

This paper introduces a flux density calibration method for AARTFAAC's all-sky images at 60 MHz, enabling real-time transient detection with an independently calibrated Northern Hemisphere source catalogue.

Contribution

It develops a new flux calibration technique using a custom 60 MHz source catalogue for real-time, accurate flux scaling of AARTFAAC images.

Findings

Created a 60 MHz source catalogue with 167 sources.

Achieved stable, real-time flux calibration for one-second images.

Enabled detection of low-frequency transients with improved accuracy.

Abstract

We present a method for calibrating the flux density scale for images generated by the Amsterdam ASTRON Radio Transient Facility And Analysis Centre (AARTFAAC). AARTFAAC produces a stream of all-sky images at a rate of one second in order to survey the Northern Hemisphere for short duration, low frequency transients, such as the prompt EM counterpart to gravitational wave events, magnetar flares, blazars, and other as of yet unobserved phenomena. Therefore, an independent flux density scaling solution per image is calculated via bootstrapping, comparing the measured apparent brightness of sources in the field to a reference catalogue. However, the lack of accurate flux density measurements of bright sources below 74 MHz necessitated the creation of the AARTFAAC source catalogue, at 60 MHz, which contains 167 sources across the Northern Hemisphere. Using this as a reference results in a sufficiently high number of detected sources in each image to calculate a stable and accurate flux scale per one second snapshot, in real-time.