2025MNRAS.538.1314Y

New multiwavelength Karl G. Jansky VLA observations of CKR02A, the compact radio source in the centre of the compact H II region NGC 6334A, are presented. The observations were carried out in five epochs and included the frequency ranges 8.0-12.0 GHz (X band), 18.0-26.0 GHz (K band), and 29.0-37.0 GHz (Ka band). The source is detected and resolved in all the observed epochs and in all bands. The source shows a clear arc-shaped structure consistent with a bow shock. The analysis of the spectral index maps indicates that its spectral index is $\alpha =-0.68\pm 0.17$, suggesting that the emission is non-thermal. Two astronomical objects can explain the emission nature and morphology of the source: a colliding wind region of two massive stars or the bow shock of a massive runaway star. However, no massive stars are reported so far in the centre of NGC 6334A, though its presence is also suggested by the free-free radio emission of the C-H II region itself. Using ancillary VLA data, we measured a preliminary proper motion of $19\pm 6$ mas yr$^{-1}$, equivalent to a velocity of $120\pm 40$ km s$^{-1}$. A detailed discussion of the implications of both scenarios is provided. Finally, a list of compact radio sources in the vicinity of NGC 6334A is given and briefly discussed.