MeerKAT reveals a ghostly thermal radio ring towards the Galactic Centre

¹ INAF – Osservatorio Astrofisico di Catania, Via Santa Sofia 78, I-95123 Catania, Italy
² Western Sydney University, Locked Bag 1797, Penrith South DC, NSW 2751, Australia
³ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
⁴ South African Radio Astronomy Observatory (SARAO), 2 Fir Street, Black River Park, Observatory, Cape Town 7925, South Africa
⁵ Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago 7630355, Chile
⁶ School of Mathematical and Physical Sciences, 12 Wally’s Walk, Macquarie University, NSW 2109, Australia
⁷ Department of Astronomy, University of Cape Town, Private Bag X3 Rondebosch 7701, South Africa
⁸ , CSIRO Space and Astronomy, Australia Telescope National Facility, PO Box 76 Epping, NSW 1710, Australia
⁹ Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia
¹⁰ Department of Astronomy, Stockholm University, The Oskar Klein Centre, AlbaNova, SE-106 91 Stockholm, Sweden
¹¹ Dublin Institute for Advanced Studies, Astronomy & Astrophysics Section, DIAS Dunsink Observatory, Dublin D15 XR2R, Ireland
¹² School of Physics, Chemistry, and Earth Sciences, The University of Adelaide, Adelaide 5005, Australia
¹³ ISDEFE, Beatriz de Bobadilla, 3, E-28040 Madrid, Spain
¹⁴ School of Natural Sciences, Private Bag 37, University of Tasmania, Hobart 7001, Australia

Received: 17 May 2024
Accepted: 22 July 2024

Abstract

We present the serendipitous discovery of a new radio-continuum ring-like object nicknamed Kýklos (J1802–3353), with MeerKAT UHF and L-band observations. The radio ring, which resembles the recently discovered odd radio circles (ORCs), has a diameter of ∼80″ and is located just ∼6° from the Galactic plane. However, Kýklos exhibits an atypical thermal radio-continuum spectrum (α = −0.1 ± 0.3), which led us to explore different possible formation scenarios. We concluded that a circumstellar shell around an evolved massive star, possibly a Wolf-Rayet, is the most convincing explanation with the present data.