Computer Science – Performance
Scientific paper
Jun 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...208.3503m&link_type=abstract
American Astronomical Society Meeting 208, #35.03; Bulletin of the American Astronomical Society, Vol. 38, p.111
Computer Science
Performance
Scientific paper
The X-ray brightest planetary nebula, BD+30 3639, was observed for 40 ksec with Suzaku in September 2005. It was detected with the XIS at a 0.2-2 keV luminosity of 1.4x1033 erg/s, in agreement with previous X-ray observations. This is only 0.1% of the kinetic luminosity supplied by fast winds from the central star, confirming that the X-rays are emitted from hot plasmas created via standing shocks in the stellar winds.Thanks to the excellent performance of the XIS, K-lines from CVI, OVII, OVIII, and NeIX were clearly resolved. After self-calibrating several residual uncertainties in the XIS response, the background-subtracted XIS spectra were successfully reproduced with a single vAPEC model of temperature 0.19 keV, absorbed by 2x1021 cm-2. The model can also reproduce the Chandra ACIS-S spectrum of the same object.The X-ray determined abundance ratios among carbon, oxygen, and neon are much more strongly deviated from the solar values than are indicated by optical observations of this object. In fact, the C/O ratio is nearly two order of magnitude higher than the solar value, and the Ne/O ratio is approximately 6 times solar. These results do not change significantly even if varying the assumed He/H ratio, or relaxing the single-temperature condition, or invoking non-equilibrium ionization conditions.The observed extreme abundance ratios indicate that the X-ray emitting plasma in BD+30 3639, carrying a minor portion of the system mass, represents a particular phase of nucleosynthesis inside the central star. The C/O ratio, 102 solar, is typical for He-shell burning products in evolved intermediate-mass stars. The enhanced Ne/O ratio may be explained by nuclear burnings from 14N to 22Ne, as a by-product of the unstable He-shell burning. Thus, the present Suzaku results on BD+30 3639 provide valuable diagnostics to the helium-burning and related processes inside an evolved star.
Arnaud A. A. K.
Hamaguchi Kenji
Hayashida Kiyoshi
Kokubun Motohide
Kotoku Jun
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