Name/Affiliation: Gregory Herczeg (KIAA/Peking University)
Optical Photospheric and Accretion Properties of Nearby T Tauri Stars
Measurements of the mass and age of young stars from their location in the HR diagram are limited by not only the typical observational uncertainties that apply to field stars, but also by large systematic uncertainties related to circumstellar phenomena. I will present results from a large spectroscopic survey of 280 nearby T Tauri stars, in which we simultaneously measure accretion, extinction, and spectral type from the full optical spectrum. The primary advances in this project are (1) the systematic incorporation of a simplistic accretion continuum in optical spectral type and extinction measurements calculated over the full optical wavelength range, (2) systematic and direct measurements of accretion rates from the Balmer continuum for a large sample, and (3) the uniform analysis of a large sample of stars, many of which are well known and can serve as benchmarks. Differences between spectral types can be subtle and difficult to discern, especially when accounting for accretion and extinction. Large discrepancies in extinction between optical and near-IR extinction measurements likely result from methodological differences. We discuss how the uncertainties in spectral type and extinction affect luminosity measurements and contribute to luminosity spreads seen in HR diagrams of young clusters.