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31st of January 2022
A transient with an unusually slow period
by Hurley-Walker et al.
Hurley-Walker et al. have reported the discovery of a transient radio-source with unusually slow periodic emission. Using data from the Murchison Widefield Array (MWA), the precursor to the SKA-Low telescope, the team detected emission with an 18.18 minute periodicity from GLEAM-X J162759.5-523504.3. The emission is highly linearly polarized, bright, persists for 30--60 s on each occurrence and is visible across a broad frequency range. By measuring the dispersion of the radio pulses with respect to frequency, the team localized the source to within our Galaxy and suggest that it could be an ultra-long-period magnetar.

The fluence of the pulses is variable but broadly follows a distribution with two "on" intervals approximately 30 days wide (3 January--2 February and 28 February--28 March 2018) and a 26-day null interval between them. The detections are all serendipitous in archival data, leading to heterogeneous coverage. During the "on" intervals, at every time when they predict they would detect a pulse, they do so (that is, there is no obvious nulling). The image above shows a selection of pulses from these "on" periods, with flux densities are normalized to the peak of each pulse for readability. The colour range spans 88 MHz (cyan) to 215 MHz (magenta) and the detections span 84 days in January to March 2018. The paper was published in last week's issue of Nature.

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