Bibcode
De Marco, O.; Chu, Y.-H.; Steffen, M.; Sokoloski, J. L.; Soker, N.; Schönberner, D.; Sandin, C.; Parker, Q. A.; Nordhaus, J.; Bujarrabal, V.; Corradi, R. L. M.; Zijlstra, A.; Behar, E.; Lopez, J. A.; Rapson, V.; Frank, A.; Guerrero, M. A.; Blackman, E.; Sahai, R.; Miszalski, B.; Frew, D. J.; Balick, B.; Montez, R., Jr.; Kastner, J. H.; Villaver, E.; Ueta, T.
Bibliographical reference
The Astronomical Journal, Volume 144, Issue 2, article id. 58 (2012).
Advertised on:
8
2012
Citations
107
Refereed citations
79
Description
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 four detections
of diffuse X-ray emission and nine 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% for the 35 sample objects. Roughly
50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while
soft, diffuse X-ray emission tracing shocks—in most cases, "hot
bubbles"—formed by energetic wind collisions is detected in ~30%;
five objects display both diffuse and point-like emission components.
The presence (or absence) 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
point-like CSPNe X-ray sources display X-ray spectra that are harder
than expected from hot (~100 kK) central stars emitting as simple
blackbodies; the lone apparent exception is the central star of the
Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest 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
<~ 5 × 103 yr, placing firm constraints on the
timescale for strong shocks due to wind interactions in PNe. The
high-energy emission arising in such wind shocks may contribute to the
high excitation states of certain archetypical "hot bubble" nebulae
(e.g., NGC 2392, 3242, 6826, and 7009).
Related projects
Bipolar Nebulae
This project has three major objectives: 1) To determine the physico-chemical characteristics of bipolar planetary nebulae and symbiotic nebulae, to help understanding the origin of bipolarity and to test theoretical models, mainly models with binary central stars, aimed at explaining the observed morphology and kinematics. 2) To study the low
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