THE CHANDRA PLANETARY NEBULA SURVEY (CHANPLANS). II. X-RAY EMISSION FROM COMPACT PLANETARY NEBULAE

We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (ChanPlaNS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within similar to 1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. ChanPlaNS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. ChanPlaNS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R-neb less than or similar to 0.4 pc), young PNe that lie within similar to 1.5 kpc. Results from these Cycle 14 observations include first-time X-ray detections of hot bubbles within NGC 1501, 3918, 6153, and 6369, and point sources in HbDs 1, NGC 6337, and Sp 1. The addition of the Cycle 14 results brings the overall ChanPlaNS diffuse X-ray detection rate to similar to 27% and the point source detection rate to similar to 36%. It has become clearer that diffuse X-ray emission is associated with young (less than or similar to 5 x 10(3) yr), and likewise compact (R-neb less than or similar to 0.15 pc), PNe with closed structures and high central electron densities (n(e) greater than or similar to 1000 cm(-3)), and is rarely associated with PNe that show H-2 emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, two of the five new diffuse X-ray detections (NGC 1501 and NGC 6369) host [WR]-type central stars, supporting the hypothesis that PNe with central stars of [WR]-type are likely to display diffuse X-ray emission.