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2nd of February 2022
An ORC near the LMC
by Filipovic et al.
Filipovic et al. report the discovery with ASKAP of J0624–6948, a low-surface brightness radio ring, lying between the Galactic Plane and the Large Magellanic Cloud (LMC). This source has phenomenological similarities to Odd Radio Circles (ORCs). However, significant differences to the known ORCs -- a flatter radio spectral index, the lack of a prominent central galaxy as a possible host, and larger apparent size -- suggest that J0624–6948 may be a different type of object. They argue that the most plausible explanation for J0624–6948 is an intergalactic supernova remnant due to a star that resided in the LMC outskirts that had undergone a single-degenerate type Ia supernova, and we are seeing its remnant expand into a rarefied, intergalactic environment. The ASKAP 888 MHz image above shows J0624–6948 in the lower left and the LMC in the upper right. The various coloured circles/ellipses represent the positions of known LMC SNRs and SNR candidates. The separation of ∼2.6 kpc indicated here assumes that J0624–6948 is at the same distance as the LMC (50 kpc). The inset in the upper left is zoomed in J0624–6948 at ASKAP native frequency of 888 MHz. The paper will be published in Monthly Notices of the Royal Astronomical Society.

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