EMU detection of mysterious multiple component radio-continuum emission from nearby spiral Seyfert I type galaxy 'Sand-timer' (NGC 7213)

M. D. Filipović; Z. J. Smeaton; B. S. Koribalski; R. Kothes; A. Ahmad; R. Z. E. Alsaberi; C. Bordiu; A. C. Bradley; E. J. Crawford; A. M. Hopkins; E. Järvelä; S. Lazarević; D. Leahy; J. L. Payne; S. F. ur Rahman; G. P. Rowell; H. Sano; M. Selby; S. S. Shabala; E. J. Stanton; S. Taziaux; K. Tsuge; D. Urosević; N. F. H. Tothill; J. Th. van Loon; V. Velović; G. L. White

arXiv · 2610.18285

EMU detection of mysterious multiple component radio-continuum emission from nearby spiral Seyfert I type galaxy 'Sand-timer' (NGC 7213)

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Abstract

We present an Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) radio-continuum detection of the nearby spiral Seyfert I type galaxy NGC 7213 which we nickname `Sand-timer' due to its morphological appearance. We find intriguing, peculiar emission extending from the central supermassive black hole (SMBH), which we refer to as galaxy hyperbubbles and/or active galactic nucleus (AGN) jets. Finally, we find two previously undetected kiloparsec-scale features in the polarised intensity image, which appear most likely also related to the central SMBH, as restarted bipolar radio jets, though somewhat obscured in the radio-continuum total intensity image. They resemble the bow shocks often seen in Fanaroff-Riley Class II (FR-II) radio galaxies, and so we propose they most likely represent an early episode of the `Sand-timer's' AGN jet activity. An alternative scenario is that the core of NGC 7213 may be a supermassive binary black hole (SMBBH) undergoing a tidal disruption event (TDE), potentially causing the peculiar radio-continuum emission.

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M. D. Filipović, Z. J. Smeaton, B. S. Koribalski, R. Kothes, A. Ahmad, R. Z. E. Alsaberi, C. Bordiu, A. C. Bradley, E. J. Crawford, A. M. Hopkins, E. Järvelä, S. Lazarević, D. Leahy, J. L. Payne, S. F. ur Rahman, G. P. Rowell, H. Sano, M. Selby, S. S. Shabala, E. J. Stanton, S. Taziaux, K. Tsuge, D. Urosević, N. F. H. Tothill, J. Th. van Loon, V. Velović, G. L. White. 2026-10-13. EMU detection of mysterious multiple component radio-continuum emission from nearby spiral Seyfert I type galaxy 'Sand-timer' (NGC 7213). https://arxiv.org/abs/2610.18285

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