IRAS 05436-0007 and the Emergence of MCNeil's Nebula

We present a study of McNeil's Nebula, a newly appeared reflection nebula in the L1630 cloud, together with photometry and spectroscopy of its source. New IR photometry compared with earlier Two Micron All Sky Survey data shows that the star has brightened by about 3 mag in the near-infrared, changing its location in a J-H/H-K^' diagram precisely along a reddening vector. A Gemini Near InfraRed Imager K-band spectrum shows strong CO band head emission, and Brγ is in emission, indicative of strong accretion. A Gemini Multi-Object Spectrograph optical spectrum shows only a red, heavily veiled continuum, with Hα strongly in emission and displaying a pronounced P Cygni profile, with an absorption trough reaching velocities up to 600 km s^-1. This implies significant mass loss in a powerful wind. However, no evidence is found for any shocks, as commonly seen in collimated outflows from young stars. Apparently the eruption has dispersed a layer of extinction, and this, together with the intrinsic brightening of the IRAS source, has allowed an earlier outflow cavity to be flooded with light, thus creating McNeil's Nebula.