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We present the first Chandra X-ray observations of H72.97–69.39, a highly embedded, potential superstar cluster in its infancy located in the star-forming complex N79 of the Large Magellanic Cloud. We detect particularly hard, diffuse X-ray emission that is coincident with the young stellar objects identified with JWST, and the hot gas fills cavities in the dense gas mapped by the Atacama Large Millimeter/submillimeter Array. The X-ray spectra are best fit with either a thermal plasma or power-law model, and assuming the former, we show that the X-ray luminosity of L _X = (1.0 ± 0.3) × 10 ^34 erg s ^−1 is a factor of ∼20 below the expectation for a fully confined wind bubble. Our results suggest that stellar wind feedback produces diffuse hot gas in the earliest stages of massive star cluster formation and that wind energy can be lost quickly via either turbulent mixing followed by radiative cooling or by physical leakage.

Stellar winds from massive stars may be significant sources of cosmic rays (CRs). To investigate this connection, we report a detailed study of gamma-ray emission near the young Milky Way star cluster (≈0.5 Myr old) in the star-forming region RCW 38 and compare this emission to its stellar wind properties and diffuse X-ray emission. Using 15 yr of Fermi-LAT data in the 0.2–300 GeV band, we find a significant ( σ > 22) detection coincident with the star cluster, producing a total gamma-ray luminosity (extrapolated over 0.1–500 GeV) of L _γ =(2.66 ± 0.92) × 10 ^34 erg s ^−1 adopting a power-law spectral model (Γ = 2.34 ± 0.04). Using an empirical relationship and STARBURST99 , we estimate the total wind power to be 8 × 10 ^36 erg s ^−1 , corresponding to a CR acceleration efficiency of η _CR ≃ 0.4 for an assumed diffusion coefficient consistent with D = 10 ^28 cm ^2 s ^−1 . Alternatively, a lower acceleration efficiency of 0.1 can produce this L _γ if the diffusion coefficient is smaller, D ≃ 2.5 × 10 ^27 cm ^2 s ^−1 . Additionally, we analyze Chandra X-ray data from the region and compare the hot-gas pressure to the CR pressure. We find the former is 4 orders of magnitude greater, suggesting that the CR pressure is not dynamically important relative to stellar winds. As RCW 38 is too young for supernovae to have occurred, the high CR acceleration efficiency in RCW 38 demonstrates that stellar winds may be an important source of Galactic CRs.