Determine the physical nature of the X-ray sources inside the radio bubble

Determine whether the faint point-like X-ray sources X1 and X2 detected within the boundary of the LEDA~217397 radio bubble are physically associated with the bubble or are unrelated background active galactic nuclei, X-ray binaries, or statistical fluctuations.

Background

The authors cross-matched the radio bubble with eROSITA catalogues and found no diffuse X-ray emission from the bubble or its shells. Two faint, low-significance point sources, X1 and X2, lie within the bubble boundary.

Because the sources are point-like and have low detection significance, they cannot presently be identified as the extended shock-heated circumgalactic-gas emission predicted by some merger-shock models. Establishing their distances and nature would determine whether they provide any evidence about the physical origin of the radio bubble.

References

Both sources are point-like at the eROSITA resolution, so they cannot represent the extended, shock-heated CGM emission predicted by the merger-shock model; given their low detection significance, they are most plausibly background AGNs, X-ray binaries, or even statistical fluctuations, and any physical association with the bubble remains unclear.

— ASKAP discovery of a pair of large radio bubbles: on the origin of odd radio circles  (2608.22835 - Su et al., 24 Aug 2026) in Section 4.2, A merger-driven shock origin?