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Session 17 - ISM, Star Formation & Planets.
Oral session, Monday, June 09
North Main Hall C/D,
We present new high resolution (R \simeq 21,000) near-infrared (\lambda = 2 \mum) spectroscopic observations of flat-spectrum young stellar objects in the \rho Ophiuchi dark cloud. These are the first observations which reveal details of the photospheres of stars at such early evolutionary stages. No clear spectroscopic signatures of line formation in Keplerian circumstellar disks are observed. The 2.294 \mum \nu = 0 - 2 CO spectra show that some of these flat-spectrum objects are rotating very rapidly (v sin i \simeq 50 km s^-1), much faster than pre-main-sequence stars with smaller infrared excesses. However, the 2.207 \mum spectral regions of these extremely young stars are more similar to those of late-type dwarf or pre-main-sequence stars than to those of stellar giants or FU Ori-type young stars. These characteristics can be understood if flat-spectrum objects have stellar structures similar to those of (more evolved) pre-main-sequence stars but are accreting mass from their circumstellar disks at rates between those of T Tauri stars and FU Ori stars.
