THE CLASSICAL T-TAURI SPECTROSCOPIC BINARY DQ-TAU .2. EMISSION-LINE VARIATIONS WITH ORBITAL PHASE

We report on echelle observations of a variety of Line profiles taken throughout the orbit of the close, eccentric binary T Tauri system DQ Tau. The stars themselves exhibit puzzling inconsistencies in the spec tral types inferred from atomic versus molecular lines. The system sho ws clear evidence of an extensive circumbinary disk. The binary is exp ected to clear a central hole in the disk; however, the line profiles are similar to those from single classical T Tauri stars. This indicat es that similar infall and outflow activities are taking place. The im plication is that material is flowing through the supposed gap in the disk. It also means that these ''classical'' profiles do not require a stable circumstellar disk for their formation, since the stellar sepa ration at periastron is too small to allow such disks. We present evid ence that accretion increases (sometimes dramatically) as the stars ap proach each other. Both continuum Veiling and emission line intensitie s can increase. In one outburst the Ca II IR Lines brighten by a facto r of 5. We discuss the line profiles during such outbursts in some det ail. Along with increased accretion, the lines sometimes also imply hi gh velocity outflows. Given the fact that outbursts can occur as much as 0.15 in phase away from closest approach, we favor accretion over d irect magnetospheric interactions as the power source of the outbursts . Away from each other, the stars resemble moderate- to low-activity c lassical T Tauri stars. There is evidence that some material is stored near the stars and ingested throughout the orbit. These observations are generally consistent with a model for disks in binary systems prop osed by Artymowicz & Lubow (1996, ApJ, 467, L77). The importance of th is system is that it provides empirical support for continuing accreti on through dynamical tidal gaps in disks. It demonstrates that very cl ose binaries can be classical T Tauri systems. (C) 1997 American Astro nomical Society.