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21st of September 2021
A VAST Pilot Survey pulsar
by Murphy et al.
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. One class of variable sources was pulsars, as illustrated above. (The X-axis is Modified Julian Day number: MJD 58600 corresponds to 27 April 2019 and MJD 59100 is 9 September 2020.)

Pulsars can be variable for reasons intrinsic to the object itself, or for external reasons relating to the propogation of the radio waves through the interstellar medium of our Galaxy, or, if they are in a binary system, due to that environment. This variability can help distinguish pulsars from background continuum sources. The pulsar shown above is not in a binary system and has not previously displayed any intrinsic phenomena, and so the variability is most likely due to refractive interstellar scintillation on longer timescales and diffractive interstellar scintillation on shorter timescales.

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