Observations of Young (Orion-Type) Stars with IRAS

Abstract

Forty-one young objects from Cohen’s (1973, 1974) lists were found to have fluxes in more than one of the IRAS bands. Some of the sources are plotted here, using filled circles for Cohen’s data and crosses for the IRAS data. Upper limits are indicated by arrows. Of the sources five were judged to have flat energy distributions, i.e. they varied by less than 0.5 decades in log λIλ. across the range 2.2µm to lOOµm. No colour correction was made to trie fluxes of these objects. Fourteen of the objects were judged to show a peak in the energy distribution in the wavelength range used here. Some, such as T Tau and GW Ori, showed evidence for two distinct peaks in their energy distributions. The remaining twenty-two were classed as having energy distributions which declined steadily with increasing wavelength. In some of the energy distributions there was evidence of a feature around 10µm, but very few of these objects were bright enough to have LRS spectra available for further examination. When a colour-colour diagram was made, using the fluxes in Janskys, with log F25 - log F12 plotted against log F60 - log F25, there was a tendency for the sources to separate into two regions, depending on whether the energy distribution was regarded as declining or peaked/flat.