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7th of October 2021
A VAST Pilot Survey variable of unknown origin
The ASKAP Variables and Slow Transients Survey (VAST) is designed to detect highly variable and transient radio sources on timescales from 5 seconds to ∼5 years. Murphy et al. have recently presented initial results from the VAST Phase I Pilot Survey. A total of 113 fields were observed for a 12 minutes integration time, with between 5 and 13 repeats, and cadences between 1 day and 8 months. An initial search revealed 28 highly variable and/or transient sources. Previous ADAPs have shown examples of pulsars and stars: the third class of variable sources were the "others". The figure above shows the light curve for one of these. (The X-axis is Modified Julian Day number: MJD 58600 corresponds to 27 April 2019 and MJD 59100 is 9 September 2020.)

A total of 14 highly variable sources were found that were not associated with a known pulsar or star. A search for optical or infrared counterparts was made using WISE, Gaia EDR3 and the Dark Energy Survey DR1 catalogues. Two of the 14 are associated with Active Galactic Nuclei, and several others have infrared properties suggesting they are galaxies, but a number of others, such as the example above, remain unclear and are the subject of ongoing study.

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