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Session 49 - Young Stellar Objects.
Display session, Tuesday, January 14
Metropolitan Ballroom,

[49.09] SU Aurigae: Two Seasons of Variability

L. E. Dewarf (Villanova U.), E. F. Guinan (Villanova U.), T. Shaughnessy (Radnor High School, Radnor, Pennsylvania)

Intensive long-term photometric monitoring has been carried out on the Classical T Tauri Star (CTTS) SU Aurigae (G2, V \approx 9 mag). "Classical" T Tauri, as opposed to "Naked" T Tauri, consist of circumstellar disk of material. SU Aur is the archetypical star for the late F to K spectral type CTTS that exhibit weak emission at H\alpha and Ca II, have very broad absorption lines (due to high values for v sin i), and are fairly luminous. H\alpha line profile variability studies have determined the rotation rate of this star to be about 3 days. Stromgren four-filter (uvby) photometry was obtained with the Automatic Photoelectric Telescopes (APTs) on Mt. Hopkins, Arizona, covering the two Taurus-Aurigae observing seasons of 1993/94 and 1994/95. The first season shows a sharp eclipse-like drop in light with maximum light losses of approximately 0.4^m in the y-band and increasing to about 0.8^m in u. The total duration of this event is around 30 days. The second season of observations show light variations that are much more slow developing and less dramatic. These data can be accurately modelled using a sinusoid; yielding a "period" of variability of around 140 \pm 5 days and amplitudes of 0.17^m in y, increasing to 0.30^m in u.

We present the analysis of the Stromgren indices, (b-y), (u-b), [c_1], and [m_1] for SU Aur and advance models that explain its photometric behavior in terms of circumstellar dust obscuration and also stellar activity. This research is supported by NSF/RUI Grant AST-93 15365, which we gratefully acknowledge

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