Complementary Insights from Helium 10830 in the Age of Interferometry

The atomic helium line at 10830 Angstroms readily shows deep absorption features on both the red and blue sides of line center. Due to helium's high excitation potential, these absorption features probe accretion and outflow, respectively, in the innermost 0.1 AU of accreting star-disk systems. I will present spectra of this transition in young stellar objects with a range of inclination angles and accretion rates, including stars that are undergoing luminosity outbursts. The profiles will be interpreted in light of recent high-resolution images of these systems that probe somewhat larger scales in the inner disk.