Spectrum of H30α line extracted from within a single beam centred upon the continuum peak location over-plotted with a Gaussian fit (dashed black). The velocity resolution is 1.4 km s⁻¹. The line is centred at 22.1 km s⁻¹ the V_LSR of G17.64 as indicated by the vertical grey line. The base flux level for the Gaussian fit was fixed to zero. The line is weak compared to the other O-star sources (Cesaroni et al. 2017) but is exceptionally broad, with a FWHM of ~81.9 ± 1.7 km s⁻¹.