[Normal Stars and WD -- Oral ]
X-rays from Planetary Nebulae: a Decade of Insight from Chandra
Joel Kastner, Rochester Institute of Technology
Planetary nebulae (PNe) represent very late stages in the
lives of stars of initial mass 1--8 $M_\odot$. As such, PNe serve as
proving grounds for theories concerning a wide range of astrophysical
phenomena, from stellar nucleosynthesis to wind interactions to the
impact of binarity on stellar evolution and the ultimate fates of binary
(and, perhaps, exoplanet) systems. In the era of Chandra and XMM-Newton,
the detection (or nondetection) of diffuse and/or point-like X-ray
sources within PNe yields important, unique information concerning the
evolutionary state of PN central star(s) and wind interactions as
nebular shaping agents. Diffuse X-ray sources allow us to probe the
energetic shocks within PN wind interaction regions, whether in the form
of wind-blown bubbles or fast, collimated outflows impinging on PN
progenitor ejecta. Chandra X-ray gratings spectroscopy of the superheated
plasma in such a wind-shock region -- within the PN BD +303639 -- has
yielded unparalleled insight into the crucial, late stages of nucleosynthesis
within this PN's progenitor star. At the same time, searches for X-ray
point sources within PNe provide a novel means to detect binary companions
at PN cores, thereby constraining models in which the formation and
shaping of PNe is directly linked to central star binarity and, perhaps,
the presence of planetary-mass companions. I present highlights within
each of these areas from among the X-ray results for PNe accumulated by
Chandra and XMM-Newton over the past decade, and I discuss the pressing,
unsolved questions in PN research that these X-ray observatories can
best address in the coming years.