8th HEAD Meeting, 8-11 September, 2004
Session 10 Stars and the Sun
Oral, Wednesday, September 8, 2004, 2:00-3:30pm

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[10.05] Does Accretion Heat the Coronae of T Tauri Stars?: The Highly Variable Mass Accretion of S CrA

F.M. Walter, J. Miner (Stony Brook University)

Since the discovery that the corona of TW Hya appears cooler and denser than is typical of the coronae of cool stars, it has again become fashionable to consider accretion heating as the direct cause of the X-ray emission in at least some of the classical T Tauri stars (Kastner et al. 2002, ApJ 567, 434). Arguably, one of the best targets for studying the case for accretion heating is S CrA.

In the 1970s and 1980s, S CrA often exhibited inverse-P Cygni line profiles, indicative of mass accretion, in the upper Balmer lines. We have revisited this system, taking advantage of the monitoring capabilities of the SMARTS facilities to compile a long-term spectrophotometric record of the brightness and line profile variations in this star. S CrA is a 1.3 arcsec visual pair, with up to 2 magnitude variations in optical brightness. Although generally dismissed as insignificant, our imaging shows that the SE component is often brighter and bluer than the NW component. We have obtained low dispersion spectra with a cadence of up to 2 spectra per night over the past year. These spectra reveal the timescales of the discrete accretion events. S CrA was detected in X-rays by ROSAT, as well as by CHANDRA. The off-axis ACIS image does not resolve the system, but does reveal a strong X-ray flare.

We will present the time-series spectra and images, and will report on our attempts to correlate the mass infall, the mass outflow, and the line and continuum brighness variations. We will make predictions for the X-ray variations in this system. The rapidity of the variations in this system present a rare opportunity to examine the interplay of discrete accretion events and atmospheric heating in an accreting T Tauri star.

This research is supported by an NSF grant to Stony Brook.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.