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10th of June 2022
Wide-band spectral variability of peaked spectrum sources
by Ross et al.
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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