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M.R. Perez (Los Alamos National Laboratory), M.E. van den Ancker (European Southern Observatory), M.D. Joner (Brigham Young University), B. McCollum (SIRTF Science Center)
Just about 20 arcminutes north-west of the Cone Nebula near the center of the open cluster NGC 2264, resides one of the most intriguing objects in this region: Walker 90 (V590 Mon, LkH\alpha 25, NGC 2264-Vas62, IRAS 06379+0950). This object, according to its spectral type (B8pe) is at least 3 magnitudes too faint in V (~ 12.7) for the cluster distance, but it shows the classical signs of a young pre-main sequence object such as highly variable H\alpha emission, Mg II emission, IR excess, and some optical variability.
According to star formation processes, this object is expected to clear its primordial surroundings by becoming optically brighter, by weakening its IR excess colors and by decreasing some line emissions. This process was thought to have occurred when Bhatt & Sagar (1992, A&AS, 92, 473), from observations taken in 1989, announced that this object was 3 magnitudes brighter at V=9.7. Unfortunately, this was demonstrated to be a false alarm. Our observations for the last decade show small variabilities (around V ~ 12.7) with some brightening trends.
We present a collection of archival and original data on Walker 90, ranging from optical photometry, to ultraviolet spectroscopic data. This object, unlike many other more evolved pre-main sequence objects, is either in the late stages of clearing its embryonic material or is directly behind a dark molecular cloud and is being affected by dense selective extinction. In either case, several other observational properties make this object very unique and enigmatic.
The author(s) of this abstract have provided an email address for comments about the abstract: mrperez@lanl.gov
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.