Natasha Hurley-Walker (Curtin)

Natasha Hurley-Walker Colloquium: Long-period radio transients

Kensington

Abstract

SKA pathfinder instruments are probing the radio sky in new ways, probing the sky on timescales hitherto poorly-explored. Sensitive image-plane surveys are discovering new kinds of radio transients, with unusual temporal, spectral, and polarisation properties. Two intriguing periodic transients were published last year: a pulsar-like object repeating every 76s that is growing fainter with time (Caleb et al. 2022), and a short-lived radio transient repeating every 18 minutes (Hurley-Walker et al. 2022a). Both are potential examples of “ultra-long period” (ULP) magnetars, and their radio emission might be explained by a temporary twisting and/or reorganisation of their intense magnetic fields.

These discoveries are spurring new searches for similar long-period sources. Last year we conducted a transient imaging survey of the Galactic plane with the MWA at 200 MHz. We were successful in detecting a further long-period transient, which compared to previous examples shows different pulse morphology, polarisation behaviour, and a staggeringly different activity window. Timing estimates place the source below the conventional “death lines” of emission mechanisms that explain radio emission in neutron stars. These sources are just the tip of the iceberg of a new population, the exploration of which will illuminate the behaviour of neutron stars and therefore physics in extreme environments. I will conclude the talk with future survey plans across a range of telescopes.