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Session 40 - The Environment of Stars: From Protostars to the Main Sequence.
Display session, Tuesday, June 11
Great Hall,

[40.04] Spectral Classification of T Tauri stars in the Orion Nebula Cluster

C. M. Hamilton, R. C. DeCoste (Connecticut College), A. J. Ferro (Steward Observatory, University of Arizona)

The use of low resolution optical spectra in determining spectral and luminosity classes of T Tauri stars in the Orion Nebula Cluster is investigated. The most accurate means of locating stars on H-R diagrams typically uses multicolor photometry to determine apparent magnitudes (e.g. V mag) and colors (e.g. B-V). However, colors can be significantly affected by interstellar and circumstellar reddening. Hence, observed colors cannot be relied on to derive effective temperatures for T Tauri stars which are frequently embedded in circumstellar disks. In the case of unknown reddening effects, the more accurate, however less precise method for determining effective temperatures and luminosities of T Tauri stars is to classify their optical spectra, a method often used for stars subject to intrinsic reddening effects. We present low resolution spectra of a well-defined sample of T Tauri stars selected from the magnitude-limited CCD survey of variable stars in the Orion Nebula Cluster conducted by Attridge and Herbst (1992 ApJL 398, L61). The spectra were obtained at the Steward Observatory 2.3-m telescope during the 1993/1994 and 1995 observing seasons. Some stars were observed during both seasons and comparisons of their spectra are made. A comparison between the spectral types we determine for these T Tauri stars with those determined by Edwards et al. (1993 AJ 106, 372) shows a systematic difference of several spectral sub classes. An investigation of spectral types of pre-main sequence stars and the effects of spectral classification errors on statistical studies of T Tauri stars is presented.

Program listing for Tuesday