2006A&A...457..183C

As part of the Red MSX Source Survey of Massive Young Stellar Objects (MYSOs) we have conducted multi-wavelength follow up observations of the well-known object V645 Cygni. We present our data on this object, whose near-infrared spectrum is exceptional and place these in context with previous observations Our observations of V645 Cyg included near/mid infrared imaging observations, ¹³CO 2-1 line observations and high signal-to-noise velocity resolved near-infrared spectroscopy. The spectrum shows P-Cygni hydrogen Brackett emission, consistent with a high velocity stellar wind. A red-shifted emission component to a number of near-IR emission lines was also uncovered. This is associated with a similar component in the Hα line. V645 Cyg is also found to have variable CO first overtone bandhead emission.The data clearly indicate that the outflow of V645 Cyg is variable. The unidentified feature in a previously published optical spectrum is identified with a receding outflow at 2000km/s. The nature of this feature, which is found in hydrogen and helium atomic lines and CO molecular lines remains a puzzle.