| Summary: | Using the Multi Unit Spectroscopic Explorer (MUSE) instrument on the Very Large Telescope, we identified three bubble nebulae (denoted as A, B, and C) around an ultraluminous X-ray source (ULX) in NGC 55. Bubble A shows a regular elliptical shape surrounding the ULX, with a morphology similar to the canonical ULX bubble around NGC 1313 X-2. It is most likely inflated by the ULX disk wind with a mechanical power close to 10 ^39 erg s ^−1 . Bubble B lies 11″ away from the ULX on the sky plane and is not contiguous to Bubble A. It displays a bow-shock-like morphology, and is likely driven by a collimated dark jet from the ULX with a mechanical power of about 3 × 10 ^38 erg s ^−1 . If this scenario is correct, we predict that Bubble B should present radio emission with a flux of about 1–10 ^2 μ Jy at 5 GHz. Bubble C appears within Bubble A, with a velocity and velocity dispersion distinct from the rest of Bubble A. Its nature is unclear and could be part of Bubble A as a result of low local density. The optical counterpart of ULX-1 exhibits broad H α , consistent with emission from a hot disk wind.
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