Reipurth 50: The Spectra

This object was discovered by Reipurth (1985) in his survey of nebulous objects in the Orion region. It was first discussed by Reipurth & Bally (1986) as the source of a powerful molecular outflow whose associated reflection nebulosity has only recently appeared in the blue lobe of the outflow. Polarization studies (Scarrott & Wolstencroft 1988) and near infrared imaging (Casali 1991) have demonstrated that the nebula is illuminated by the IRAS source. Recent longslit spectroscopic work (Strom & Strom 1993) has demonstrated that Re 50 is probably a heavily embedded FU Ori object (Hartmann, Kenyon & Hartigan 1993) currently in outburst.

This is a plot of part of the spectrum of Re 50 taken by placing the slit of the spectrograph along the brightest part of the reflection nebulosity. The Halpha line (6563 Å) profile shows the distinctive signature of an FU Ori star, with the extent of the blue wing of this line indicating extreme outflow velocities (up to 1000 km/s for Re 50!).

Another interesting spectral region is the region around the infrared Ca triplet. These 3 lines (8498, 8542, & 8662 Å) all appear in emission. A variety of behavior is seen among the FU Ori objects in these lines.

Here is a broader view of the spectrum of this object at red wavelengths. The dashed lines show wavelengths at which the subtraction of the emission lines in the night sky was imperfectly done.

Here we see the spectral energy distribution for this object using broad band photometry from wavelengths as short as 1.25µm to a wavelength as long as 1300µm. The steep falloff in energy on the blue side is due to the extreme extinctions seen toward this object. The "hump" shortward of 10µm indicates that this light is reaching us via scattering, probably taking place in the near vicinity of the object. The emission in the region from 10 to 100µm comes from the "warm" dust also in the immediate vicinity of the object. The falloff on the red side is just the Rayleigh-Jeans falloff on the red side of the blackbody distribution. Measurements in this region of the spectrum are used to estimate the mass of dust and gas associated with this object (in the circumstellar disk and envelope).


Casali, M. 1991, MNRAS, 248, 229

Hartmann, L., Kenyon, S.J. & Hartigan, P. 1993 in Protostars and Planets III, ed E.H. Levy & J.I. Lunine (Univ. AZ Press)

Reipurth, B. 1985, A&AS, 61, 319

Reipurth, B. & Bally, J. 1986, Nature, 320, 336

Scarrott, S.M. & Wolstencroft, R.D. 1988, MNRAS, 231, 1019

Strom, K.M. & Strom, S.E. 1993, ApJ Letters, 412, L63

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