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Observations of T-Tauri Stars using HST-GHRS: II. Optical and Near UV lines

David R. Ardila·Gibor Basri·Frederick M. Walter·Jeff A. Valenti·Christopher M. Johns-Krull
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Abstract

We have analyzed GHRS data of eight Classical T Tauri stars (CTTSs) and one Weak T Tauri star (WTTS). The GHRS data consist of an spectral range 40 A wide centered on 2800 A. For 4 of the CTTS we have nearly simultaneous optical observations which contain Halpha, Hbeta, HeI, NaD, and the CaII infrared triplet. The MgII resonance doublet is the strongest feature in the 2800 A range. This line has a fairly wide and symmetric emission component (~200 to \~300 km/s for the CTTSs), with a narrow central absorption and a wide blueshifted absorption superimposed to it. The narrow central absorption width and equivalent width are inconsistent with being due only to ISM clouds described in the literature, which lead us to conclude that it is partially due to non-LTE processes in the emission line region itself. The emission profile closely follows Halpha. Its large width in CTTS cannot be due to the Stark effect and we suggest that it is due to supersonic turbulence. All the stars show blueshifted absorptions that are evidence of outflows (terminal velocities \~300 km/s), with multiple flows observed in two stars. We show evidence that the wind is not spherical, with wind signatures being stronger for lower inclinations at a given accretion rate. We briefly compare other optical lines with the hot transition region lines observed in CTTS.

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David R. Ardila, Gibor Basri, Frederick M. Walter, Jeff A. Valenti, Christopher M. Johns-Krull. 2001-11-09. Observations of T-Tauri Stars using HST-GHRS: II. Optical and Near UV lines. https://arxiv.org/abs/astro-ph/0111182

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