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| Paper: |
Optical Flares of Weak-Line and Classical T Tauri stars |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1701 |
| Authors: |
Guenther, Eike; Ball, Mathias |
| Abstract: |
One of the most important arguments for the presence of magnetic fields on classical T Tauri stars (cTTSs) and Weak-Line T Tauri stars (WTTSs) is the observation of flares in the X-ray regime (see also Guenther 1997). Although, flares have been observed in WTTSs in the optical regime, and although rapid changes of the brightness of cTTSs were seen in the optical regime, it was never quite clear whether these events in the cTTS were rapid changes of the accretion rate, or flares, because of the lack of spectra. Progress in this field was hitherto severely hindered because of the rarity of the events. However, multi-object spectrographs on Schmidt telescopes now allow us to monitor many stars simultaneously, thus boosting the probability of detecting flares enormously. In 1996 and 1997 we have monitored the Taurus and Chamaeleon star-forming regions using the multi-object spectrographs on the Schmidt telescopes in Tautenburg, and Siding Springs in order to study short time variability on T Tauri stars. Apart from many ``accretion events'', we have unambiguously detected many flares on WTTSs and cTTSs. Our observations thus clearly demonstrate that cTTSs have optically observable flares. Additionally, we have monitored the stars in the alpha Persei cluster, and find a much lower flare-rate than for the T Tauri stars. |
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