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T. P. Greene (NASA / Ames )
The stellar properties of embedded protostars -- those still accreting matter at significant rates -- have been largely unknown. The very high extinctions (Av \geq 50 mag) of these objects make them impossible to observe in visible light with high-resolution spectrographs. Further, these objects are also not exceptionally bright in the near-IR (K ~10 mag), and they have very large continuum veilings (r ~3) at these wavelengths, greatly diluting the strength of their photospheric absorption lines.
Despite these difficulties, high-resolution absorption spectra of some protostars have been recently obtained using sensitive IR spectrographs on large telescopes. These data show that protostars with flat-spectrum and Class I spectral energy distributions have spectral types and surface gravities similar to more evolved T Tauri stars. However, the small number of embedded protostars observed to date have considerably different v sin i rotation velocities. These objects appear to be rotating significantly faster than most T Tauri stars; typical protostar rotation velocities are v sin i ~ 40 km s-1. Recent ASCA and Chandra X-ray observations have also suggested that these protostars have short rotation periods.
We present some of these recent results and discuss some plausible mechanisms which may be responsible for the high rotation rates of protostars. These observations are in their infancy, but they may prove essential for understanding star -- disk interactions at very early ages.
Much of this work has been funded by the NASA, and we are also grateful to NASA for providing observing time on the Keck and IRTF telescopes.
The author(s) of this abstract have provided an email address for comments about the abstract: tgreene@arc.nasa.gov
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.