T Chamaeleontis : a "weak-line" YY Orionis star ?
Abstract
We present new low and high resolution spectroscopy and optical photometry of the star T Cha. From the low resolution spectroscopy we classify T Cha as a G8 type star. We also identify T Cha as the optical counterpart of the ROSAT all- sky survey X-ray source RX J1 157.2-7921. On the basis of the physical association with the Chamaeleon cloud complex, the erratic photometric variability and colour behaviour, the presence of Hα emission and of strong Li λ 6708 absorption line, as well as its position on the HR diagram, we establish unambiguously the low-mass PMS nature of the star.
These characteristics, combined with an observed equivalent width of the Hot emission less than 10 Å, suggest that the star can be classified as a weak-line T Tauri star. However, the strong IR excess of the star, resembling more closely those of classical T Tauri stars, clearly indicates the presence of a circumstellar disk. From spectra obtained at different epochs we find that strong variability is present in the Hot line, with the profile changing from pure emission to an inverse P Cygni on a time scale of one day or less. Actually, T Cha is the first case in which an inverse P Cygni profile is observed at Hα. Hence, here we suggest that T Cha can be considered a case of "weak-line" YY Orionis star.- Publication:
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Astronomy and Astrophysics
- Pub Date:
- May 1993
- Bibcode:
- 1993A&A...272..225A
- Keywords:
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- stars: T Cha;
- stars: pre-main-sequence;
- photometry;
- spectroscopy