Disk evolution -- Oral Presentation
X-ray diagnostics of pre-main sequence accretion and outflow
activity
Joel Kastner, Rochester Institute of Technology
I summarize the mounting evidence for a direct link betweenpre-main sequence (pre-MS) X-ray emission and pre-MS accretion andoutflow processes. Such a link is supported by three lines ofobservational inquiry rendered feasible by the extraordinarycapabilities of the Chandra and XMM-Newton X-ray observatories,working in concert with space- and ground-based imaging andspectroscopy in the optical and infrared regimes. These threads are:(1) the measurement of anomalous line ratios of He-like ions in high-resolution
X-ray spectra of certain young, actively accreting, low-mass (classical
T Tauri) stars; (2) the detection of an X-ray eruption from V1647 Ori
(``McNeil's Star'') that coincided with the accretion-driven optical/infrared
outburst from this dust-enshrouded protostar; and (3) the discovery of
soft X-ray emission from the immediate vicinities of pre-MS stars that
drive well-collimated outflows. Taken together, these results indicate
that, in addition to solar-like coronal activity, X-rays may be produced
by pre-MS stars via a variety of mechanisms, including accretion shocks,
disk wind shocks, and star-disk magnetic reconnection events. Further
progress will require intensive modeling efforts as well as sensitive,
high-resolution X-ray spectroscopic surveys involving much larger
samples of pre-MS stars.