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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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