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Register a new userAARTFAAC Flux Density Calibration and Northern Hemisphere Catalogue at 60 MHz
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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.
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We report the experimental setup and overall results of the AARTFAAC wide-field radio survey, which consists of observing the sky within 50$^circ$ of Zenith, with a bandwidth of 3.2$,$MHz, at a cadence of 1$,$s, for 545$,$h. This yielded nearly 4 million snapshots, two per second, of on average 4800 square degrees and a sensitivity of around 60$,$Jy. We find two populations of transient events, one originating from PSR$,$B0950$+$08 and one from strong ionospheric lensing events, as well as a single strong candidate for an extragalactic transient, with a peak flux density of $80pm30$$,$Jy and a dispersion measure of $73pm3,mathrm{~pc~cm^{-3}}$, We also set a strong upper limit of 1.1 all-sky per day to the rate of any other populations of fast, bright transients. Lastly, we constrain some previously detected types of transient sources by comparing our detections and limits with other low-frequency radio transient surveys.
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