THE OPTICAL COUNTERPART OF IRAS 12496-7650 - A HIGHLY EMBEDDED HERBIG AE STAR

We report optical and near-infrared observations of IRAS 12496 - 7650, an active young star and the most luminous IRAS source in the Chamaeleon II dark cloud. The object has become brighter at optical wavelengths since 1976, and has exhibited brightness variations of more than a magnitude at K between January 1987 and May 1990. IRAS 12496 - 7650 is redder when fainter, and the amplitude of the brightness fluctuations decreases towards longer infrared wavelengths. Differing amounts of circumstellar extinction or intrinsic color variations of the source can produce most of the observed variability. Optical spectra confirm that IRAS 12496 - 7650 is an extremely active (probably Herbig Ae type) star with blueshifted forbidden lines of [O I] and [S II] and a prominent P-Cygni profile at H-alpha. The [S II] emission extends 3-4 arcsec on either side of the star and shows a significant velocity gradient, suggestive of a jetlike structure. The detection of outflowing material from IRAS 12496 - 7650 reinforces earlier evidence that this object is the exciting source for the HH 52-54 group Herbig-Haro objects. The broad spectral energy distribution suggests that IRAS 12496 - 7650 has a circumstellar disk.