The Activity of Weak-Lined T Tauri Stars
Session 9 -- Protostars, Young Stars and Stellar Accretion Disks
Display presentation, Monday, June 12, 1995, 9:20am - 6:30pm

## [9.04] The Activity of Weak-Lined T Tauri Stars

Alan D.~Welty, Lawrence W.~Ramsey (Penn State)

We have conducted intensive spectroscopic observing campaigns on several weak-lined and classical T Tauri stars (WTTS, CTTS). The data were obtained with the Penn State Fiber Optic Echelle spectrograph in three observing runs at the KPNO 2.1m telescope. We wish to understand the phenomenology of stellar and circumstellar activity of our targets, and to quantify the activity where possible. Here we present results for our WTTS targets, V410 Tau in particular.

The first step in our analysis is to determine the spectral type of each target by fitting a grid of standard star spectra to the target star spectra. Byproducts of this process are values for radial and projected rotational velocities and veiling for each observation. We find no veiling (from H$\beta$ to H$\alpha$) in any of our targets.

Results for V410 Tau are dramatic. The photospheric temperature distribution (recently Doppler imaged by Strassmeier, Welty, \& Rice 1994 and Hatzes 1995) causes line profile variations which cause apparent radial velocity changes. The amplitude of this variability is 500 times the Sun's orbital motion due to Jupiter. Although this is an extreme case, it serves to illustrate the point that radial velocity searches for low mass companions, especially planets, must take stellar activity into account. Three of our other WTTS targets show similar radial velocity variation.

We also feature flare observations of V410 Tau. One event was observed rising and declining during one observing night. Its total duration was about 15 hours. It released $\sim10^{35}$ erg in optical line emission. He D$_3$ radial velocities enable us to locate the flare with respect to features in the Doppler images.

Our results suggest that V410 Tau has entered a state of relatively high activity after a decline indicated by various observations made during the 1980s.

We will also be pleased to discuss results on our CTTS targets with interested parties.