The Automatic Radio Burst Search System at Nasu Observatory

Abstract

In order to search for radio bursts in radio transient objects, we have developed an automatic radio burst search system. The system is being used at Nasu Pulsar Observatory of Waseda University in Jiyu-Gakuen Nasu Farm, 160 km north of Tokyo. The drift-scan fringe data from four different declinations are simultaneously obtained with an eight-element interferometer. Using the automatic radio burst search system, some radio transients were detected. Here we discuss its fringe-finding algorithms and the application in burst search observations. The application is similar to that of the blink comparator in optical telescopes to search for novae.

Proposal for Multi-Messenger Observations of Radio Transients by Nasu and Ligo-Virgo

“…If a point source passes through the fringe beam of the Nasu interferometers, the beam pattern (defined as the product of the primary beam and the fringe pattern, spaced at ∼40-46 seconds), appears in the data (Kuniyoshi et al 2006;Takefuji 2007). The method of searching for radio transients is the same as for normal radio sources: the fringe signal is identified as coming from a transient source if the beam pattern appears clearly.…”

“…Four different declinations are monitored simultaneously with four fringe beams. Observations are performed as an earth-rotation drift-scan (Kuniyoshi et al 2006). For any direction within ±5 • of the zenith, a declination of +32 • −42 • is observable by moving a symmetrical Gregorian sub-reflector.…”

Reliability of Radio Transients Detected in the Nasu Sky Survey

“…The data were recorded in the remaining 1800 s while the observation stopped. The specifications of the system are detailed in Takeuchi et al (2005), Kuniyoshi et al (2006), and Niinuma et al (2007b).…”

“…The spectral amplitude S indicates the intensity of a detected fringe and is proportional to source flux density. STFT analysis tools were developed by Kuniyoshi et al (2006) and Takefuji et al (2007), where a rectangular window was adopted. Using these tools, we detected fringes with strong intensity at a signal frequency of f s = 1/Δt s , i.e.,f s = nt smp /Δt s .…”

“…The calculations are detailed in Kuniyoshi et al (2006) and Takefuji et al (2007). Note that the calculation procedure of the former authors differs from that of the latter authors.…”