A Southern-Hemisphere all-sky radio transient monitor for SKA-Low prototype stations

Abstract

We present the first southern-hemisphere all-sky imager and radio-transient monitoring system implemented on two prototype stations of the low-frequency component of the Square Kilometre Array. Since its deployment the system has been used for real-time monitoring of the recorded commissioning data. Additionally, a transient searching algorithm has been executed on the resulting all-sky images. It uses a difference imaging technique, and has enabled identification of a wide variety of transient classes, ranging from human-made radio-frequency interference to genuine astrophysical events. Observations at the frequency 159.4 MHz and higher in a single coarse channel (0.926 MHz) were made with 2s time resolution, and multiple nights were analysed. Despite having modest sensitivity (~few Jy/beam), using a single coarse channel and 2-s imaging, the system detected bright transients from PSR B0950+08, proving that it can be used to detect bright transients of an astrophysical origin. The unusual, extreme activity of the pulsar PSR B0950+08 (up to ~155 Jy/beam) was initially detected in a "blind" search in the 2020-04-10/11 data and later assigned to this specific pulsar. The limitations of our data, however, prevent use from making firm conclusions of the effect being due to a combination of refractive and diffractive scintillation or intrinsic emission mechanisms. The system can routinely collect data over many days without interruptions; the large amount of recorded data at 159.4 and 229.7 MHz allowed us to determine a preliminary transient surface density upper limit of $1.32\times 10^{-9}{\text{deg}}^{-2}$ for a timescale and limiting flux density of 2s and 42 Jy, respectively. We plan to extend the observing bandwidth to tens of MHz and improve time resolution to tens of milliseconds in order to increase the sensitivity and enable detections of Fast Radio Bursts below 300 MHz.

22 pages, 11 figures, 3 tables, Accepted for publication in PASA

References in corpus (16)

• The NumPy array: a structure for efficient numerical computation
• Statistical properties of giant pulses from the Crab pulsar
• Bright Giant Pulses from the Crab Nebula Pulsar: Statistical Properties, Pulse Broadening and Scattering due to the Nebula
• Detection of Radio Emission from Fireballs
• Beaming structures of Jupiter's decametric common S-bursts observed from LWA1, NDA, and URAN2 radio telescopes
• Limits on GRB Prompt Radio Emission Using the LWA1
• Signal Processing Firmware for the Low Frequency Aperture Array
• Fluctuation dynamo at finite correlation times and the Kazantsev spectrum
• A survey of spatially and temporally resolved radio frequency interference in the FM band at the Murchison Radio-astronomy Observatory
• New Limits on the Low-frequency Radio Transient Sky Using 31 hr of All-sky Data with the OVRO-LWA
• Detection of a Low-frequency Cosmic Radio Transient Using Two LWA Stations
• Simultaneous Observations of Giant Pulses from Pulsar PSR B0950+08 at 42 MHz and 74 MHz
• Sensitivity of a Low-Frequency Polarimetric Radio Interferometer
• Discovery of a Pulsar Wind Nebula around B0950+08 with the ELWA
• A Low Frequency Blind Survey of the Low Earth Orbit Environment using Non-Coherent Passive Radar with the Murchison Widefield Array
• Observing Flare Stars Below 100 MHz with the LWA

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• Calibration of an SKA-Low Prototype Station Using Holographic Techniques
• A Matched Survey for the Enigmatic Low Radio Frequency Transient ILT J225347+862146