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K. Haisch (Utah Valley State College), M. Barsony (San Francisco State University), T. Greene (NASA Ames Research Center), M. Ressler (JPL)
We present the results of new mid-infrared observations of 64 Class I/flat-spectrum objects in the Perseus, Taurus, Chamaeleon I and II, Rho Ophiuchi, and Serpens dark clouds. These objects represent a subset of the young stellar objects (YSOs) from our previous near-infrared multiplicity surveys. We detected 45/48 (94%) of the single sources, 16/16 (100%) of the primary components, and 12/16 (75%) of the secondary/triple components of the binary/multiple objects surveyed. While the composite spectral energy distributions for all of our sample YSOs are either Class I or flat-spectrum, the individual source components typically display Class II, or in one case Class III, spectral indices, and frequently display mixed pairings; Class I objects paired with a flat-spectrum source, or a flat-spectrum source paired with a Class II YSO. Such behavior is not consistent with what one typically finds for T Tauri stars (TTS), where the companion of a classical TTS also tends to be a classical TTS, although other mixed pairings have been previously observed among Class II YSOs. In general, the individual binary/multiple components suffer very similar extinctions, Av, suggesting that most of the line-of-sight material is either in the foreground of the molecular cloud or circumbinary. ISO-Cha I 97 was previously detected as a single star in our near-infrared imaging survey of binary/multiple Class I and flat-spectrum YSOs, however our mid-infrared observations have revealed that this source is in fact binary. With a spectral index of \alpha > 3.9, ISO-Cha I 97 is a member of a rare class of very steep spectral index YSOs, those with \alpha > 3.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.