A Pilot Survey for Astronomical Low Frequency Radio Transients

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Virginia Tech


Dispersed low-frequency radio astronomical pulses may result from exploding primordial black holes, gamma ray bursts, supernovae, or mergers of exotic objects, but have not yet been detected. Detection would be of great scientific significance because such events must involve extreme physics. The transient nature of these events makes detection unlikely with traditional instruments due to lack of sensitivity to single pulses and narrow field of view. For this thesis, a low-frequency wide-bandwidth astronomical search instrument has been developed as an alternative approach. This instrument consists of a single dipole which yields all-sky field of view, albeit at reduced sensitivity. The spectrum from 37 - 55 MHz is coherently digitized at 200 million samples per second, recorded, and analyzed off-line for the presence of dispersed pulses. A preliminary survey has been made at a remote site in western North Carolina. In a 20 minute observation, 9 detections greater than 6.5σ occurred, corresponding to pulses of ≤ 20 ms duration and dispersion measures (DMs) ranging from 15 to 70 pc cm⁻³. In addition, groups of pulses were detected ( 5) at DMs of 43.1, 52.1, and 52.2 pc cm⁻³. The possibility of association with known pulsars is considered; however, it is also possible these are due simply to radio frequency interference. Improvements to this instrument and survey technique are suggested.



digital signal processing, radio astronomy, astronomical transients