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Characterising the spectral variability of radio sources offers the
ability to determine the astrophysics of the intervening media, source
structure, emission and absorption
processes.
Ross et al. present broadband (0.072–10 GHz) spectral variability
of 15 peaked-spectrum sources with the Murchison Widefield Array (MWA)
between 72 and 231 MHz, and the Australia Telescope Compact Array
(ATCA) between 1 and 10 GHz. These 15 peaked-spectrum sources were
observed quasi-contemporaneously with the MWA and ATCA four to six
times during 2020 with approximately a monthly cadence. Thirteen of
the 15 targets show significant variability with the MWA at megahertz
frequencies, which Ross et al. conclude is most likely due to
refractive interstellar scintillation of a compact source component.
The source GLEAM J020507–110922 was of particular interest due to the
sudden change in spectral shape in September 2020 and the increase in
peak frequency by ∼100 MHz, as shown above. The authors determine two
likely origins for the variability in this source: The variability of
GLEAM J020507–110922 prior to September 2020 is consistent with
Inter-Stellar Scintillation, however the change in spectral shape from
July to September suggests small-scale structures within the
scintillating screen, possibly an inhomogeneous ionized cloud
surrounding the source.
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