Poster Abstracts

Name/Affiliation:  Joel Kastner (Rochester Institute of Technology)

Title:  V4046 Sgr: Touchstone to Investigate Spectral Type Discrepancies for Pre-main Sequence Stars

The potential for significant discrepancies between optical and near-IR spectral type determinations for a given late-type, pre-main sequence (pre-MS) star clearly has profound implications for astronomers' ability to ascertain the fundamental properties of such stars (i.e., effective temperatures, surface gravities, masses, and ages). To address this important issue, we have obtained near-IR spectroscopy of the nearby, close binary T Tauri system V4046 Sgr AB with the NASA Infrared Telescope Facility (IRTF) SPEX spectrometer. The V4046 Sgr system provides an important test case in this regard, due to the stringent constraints on its mass (a total of ~1.8 Msun, with roughly equal-mass components) that are imposed by interferometric CO imaging of its extended circumbinary disk combined with its relatively well-determined age (12-21 Myr) and distance (73 pc). The IRTF data indicate that the composite near-IR spectral type for V4046 Sgr AB is significantly later than the (K5+K7) composite type previously determined from optical spectroscopy. We discuss the implications of these results for studies that rely on near-infrared spectroscopy to infer the photospheric temperatures and, hence, the ages and masses of pre-MS stars via placement on pre-MS evolutionary tracks.