We present the results of the first X-ray gratings spectroscopy observations of a planetary nebula ( PN ) , the X-ray-bright , young BD+30 ^ { \circ } 3639 .
We observed BD+30 ^ { \circ } 3639 for a total of 300 ks with the Chandra X-ray Observatory ’ s Low Energy Transmission Gratings in combination with its Advanced CCD Imaging Spectrometer ( LETG/ACIS-S ) .
The LETG/ACIS-S spectrum of BD+30 ^ { \circ } 3639 is dominated by H-like resonance lines of O viii and C vi and the He-like triplet line complexes of Ne ix and O vii .
Other H-like resonance lines , such as N vii , as well as lines of highly ionized Fe , are weak or absent .
Continuum emission is evident over the range 6–18 Ã .
Spectral modeling indicates the presence of a range of plasma temperatures from T _ { x } { \sim } 1.7 { \times } 10 ^ { 6 } K to 2.9 { \times } 10 ^ { 6 } K and an intervening absorbing column N _ { H } \sim 2.4 \times 10 ^ { 21 } cm ^ { -2 } .
The same modeling conclusively demonstrates that C and Ne are highly enhanced , with abundance ratios of C/O { \sim } 15–45 and Ne/O { \sim } 3.3–5.0 ( 90 % confidence ranges , relative to the solar ratios ) , while N and Fe are depleted , N/O { \sim } 0.0–1.0 and Fe/O { \sim } 0.1–0.4 .
The intrinsic luminosity of the X-ray source determined from the modeling and the measured flux ( F _ { X } = 4.1 \times 10 ^ { -13 } ergs cm ^ { -2 } s ^ { -1 } ) is L _ { X } \sim 8.6 \times 10 ^ { 32 } erg s ^ { -1 } ( assuming D = 1.2 kpc ) .

These gratings spectroscopy results are generally consistent with earlier results obtained from X-ray CCD imaging spectroscopy of BD+30 ^ { \circ } 3639 , but are far more precise .
Hence the Chandra/LETGS results for BD+30 ^ { \circ } 3639 place severe new constraints on models of PN wind-wind interactions in which X-ray emitting gas within PNs is generated via shocks and the plasma temperature is moderated by effects such as heat conduction or rapid evolution of the fast wind .
The tight constraints placed on the ( nonsolar ) abundances directly implicate the present-day central star — hence , ultimately , the intershell region of the progenitor asymptotic giant branch star — as the origin of the shocked plasma now emitting in X-rays .