MeerKAT uncovers the physics of an Odd Radio Circles: A suggested Annulus theory:
Regarding the recently discovered ORC phenomenon. It’s not clear but all the available reference on these rings suggests these various ORC are all the same size of 1 arc minute regardless of there assumed distance from the earth observer. If this is correct it’s odd that they would all just happen to be the same visual size in the observers image plane. Despite being attributed to galactic sources at various different cosmological distances. If so, this is a strange phenomena indeed. That aside;
However this paper has an image of an ORC (called ORC 1 in the paper in figure 1 from the paper) that is interesting. The assumption is that in this case (and generally with the other OCD’s ) the rings in this image are two intersecting expanding circles of some sort of ejecta rings that are orthogonal to each other. And that these expanding thin circles are actually “bubbles”. But because the bubbles ejecta density is relatively thin we only see the edge of each bubble ring where the overall density is greatest. The problem with this model is that in the above cited Norris et al figure 1 image of ORC 1 the bubble rings are not perfect circles. Which they would have to be if they were just the optically more dense edge of each of the two bubbles. In other words the ORC 1 "rings" could not be caused by expanding bubbles of ejecta, because they do not appear to us in the image as two perfectly circular overlapping rings. Something they would have to be to be explained by the usual bubble ejecta theory. Note in the cited ORC image the rings are flattened elipses Not perfect circles.
To explain ORC-1 using the usual bubble ejecta model mentioned in various different reference and particularly in Norris et al, my idea is that, in this case at least, these are two seperate ejecta bubbles expanding out from two seperate slightly offset central sources. Each source separated by a small distance on the image plane. We see only the circular rings of the edge of the bubbles where the ejecta is more optically dense. And that these two expanding spherical bubbles are overlapping with each other and forming a third internal expanding annulus ring (as shown in the illustration below) as they expand. Rather than a two separate flattened expanding rings from the same source that are orthogonal to each other as is usually interpreted from the cited image.
If one studies the image from the paper, the outer slightly flattened elipse is in fact a combination of the visible edges of 2 separate circular ejecta bubbles. And the internal orthogonally skewed ring is in fact the annulus ring denoting where the two seperate bubbles interact orthoganally with each other. Indicating that these are two seperate bubble shockwaves of ejected material with a third internal annulus ring where the two intersect.
Of course the problem here is that the coincidence of two seperate neighbouring bubbles erupting at the same time is statistically pretty small. However it’s possible that this small statistical probability explains why this type of ORC 1 observations as described in the Norris et al paper are fairly uncommon.