Mc Neil's Nebula in Orion: the Outburst History

We present a sequence of I-band images obtained at the Venezuela 1m Schmidt telescope during the outburst of the nebula recently discovered by J.W. McNeil in the Orion L1630 molecular cloud. We derive photometry spanning the preoutburst state and the brightening itself, a unique record including 14 epochs and spanning a time scale of ∼ 5 years. We constrain the beginning of the outburst at some time between Oct. 28 and Nov. 15, 2003. The light curve of the object at the vertex of the nebula, the likely exciting source of the outburst, reveals that it has brightened ∼ 5 magnitudes in about 4 months. The time scale for the nebula to develop is consistent with the light travel time, indicating that we are observing light from the central source scattered by the ambient cloud into Based on observations obtained at the Llano del Hato National Astronomical Observatory of Venezuela, operated by CIDA for the Ministerio de Ciencia y Tecnoloǵıa, and at the Fred Lawrence Whipple Observatory of the Smithsonian Institution, USA Research Associate at SAO, 60 Garden St., Cambridge, MA 02138, USA Postgrado en F́ısica Fundamental, Universidad de los Andes, Mérida, Venezuela Summer Student at CIDA, Mérida, Venezuela