Fundamental Stellar Parameters for Weak-lined T-Tauri Stars in the Rho Ophiuchus and Chamaeleon I & II Star-Forming Regions

A. Richert, D. J. James, J. Bouvier, C. Melo, N. C. Santos, A. Aarnio

Abstract
Using optical photometry and spectroscopy, we have observed X-ray selected, pre-main sequence Weak-lined T-Tauri Stars [WTTS] in the Rho Ophiuchus and Chamaeleon I & II star-forming regions. We exploit these observations in order to determine fundamental stellar characteristics of these WTTSs, such as age and mass. Membership of their parent associations was determined by 1-d radial velocity measurements as well as the significant presence of the age-sensitive, neutral resonance doublet of lithium at 6708A in our high-resolution spectra. Visible and infrared photometric data (in Johnson-Cousins BVIc and 2MASS JHKs filters) were used to obtain four color-dependent estimates of line-of-sight extinction coefficients (Av), which provides evidence of color-excesses due to the presence of any circumstellar disk material.
Spectral types were used to determine stellar temperatures and bolometric corrections, which, along with extinction-corrected V magnitudes, allowed us to calculate four sets of color-dependent bolometric luminosities scaled to the solar value. These data, plotted on HR-diagrams, allow us to determine four independent sets of stellar ages and masses of WTTSs in each star-forming region by comparison of their empirical data to theoretical isochrones and mass-tracks. In the Chamaeleon I & II regions, we find no evidence for a color-dependent age determination of its WTTSs, however in Rho Ophiuchus, we find that isochronal ages are a function of the photometric color used to determine their extinction coefficients.

AAS 217th Meeting, Seattle, Washington
(Eds.)

American Astronomical Society
Vol. 43,
2011