Article

The Chandra X-ray Survey of Planetary Nebulae (ChanPlaNS): Probing Binarity, Magnetic Fields, and Wind Collisions

The Astronomical Journal (Impact Factor: 4.97). 04/2012; 144(2). DOI: 10.1088/0004-6256/144/2/58
Source: arXiv

ABSTRACT We present an overview of the initial results from the Chandra Planetary
Nebula Survey (ChanPlaNS), the first systematic (volume-limited) Chandra X-ray
Observatory survey of planetary nebulae (PNe) in the solar neighborhood. The
first phase of ChanPlaNS targeted 21 mostly high-excitation PNe within ~1.5 kpc
of Earth, yielding 4 detections of diffuse X-ray emission and 9 detections of
X-ray-luminous point sources at the central stars (CSPNe) of these objects.
Combining these results with those obtained from Chandra archival data for all
(14) other PNe within ~1.5 kpc that have been observed to date, we find an
overall X-ray detection rate of ~70%. Roughly 50% of the PNe observed by
Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing
shocks formed by energetic wind collisions is detected in ~30%; five objects
display both diffuse and point-like emission components. The presence of X-ray
sources appears correlated with PN density structure, in that molecule-poor,
elliptical nebulae are more likely to display X-ray emission (either point-like
or diffuse) than molecule-rich, bipolar or Ring-like nebulae. All but one of
the X-ray point sources detected at CSPNe display X-ray spectra that are harder
than expected from hot (~100 kK) central star photospheres, possibly indicating
a high frequency of binary companions to CSPNe. Other potential explanations
include self-shocking winds or PN mass fallback. Most PNe detected as diffuse
X-ray sources are elliptical nebulae that display a nested shell/halo structure
and bright ansae; the diffuse X-ray emission regions are confined within inner,
sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have
inner shell dynamical ages <~5x10^3 yr, placing firm constraints on the
timescale for strong shocks due to wind interactions in PNe.

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