AAS 207th Meeting, 8-12 January 2006
Session 185 UV to IR Observations of Protostars
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

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[185.04] Mid-Infrared Observations of Class I/Flat-Spectrum Systems in Six Nearby Molecular Clouds

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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