XMM-Newton RGS observations of the Cat's Eye Nebula

TL;DR

This study analyzes high-resolution X-ray spectra of the Cat's Eye Nebula, revealing a hot plasma with specific elemental abundances and temperature, and compares it to other planetary nebulae.

Contribution

First high-resolution X-ray spectroscopic analysis of NGC 6543, providing insights into its plasma temperature and elemental composition.

Findings

Detected O VII triplet at 22 Å in the spectrum.

Plasma temperature estimated at 0.147 keV (1.7 MK).

X-ray emission shows no overabundance of C and Ne.

Abstract

We present an analysis of XMM-Newton Reflection Grating Spectrometer (RGS) observations of the planetary nebula (PN) NGC 6543, rendering it the second PN with high resolution X-ray spectroscopic observations besides BD+30 3639. The observations consist of 26 pointings, of which 14 included RGS observations for a total integration time of 435 ks. Many of these observations, however, were severely affected by high-background levels, and the net useful exposure time is drastically reduced to 25 ks. Only the O VII triplet at 22 \AA\ is unambiguously detected in the RGS spectrum of NGC 6543. We find this spectrum consistent with an optically thin plasma at 0.147 keV (1.7 MK) and nebular abundances. Unlike the case of BD+30 3639, the X-ray emission from NGC 6543 does not reveal overabundances of C and Ne. The results suggest the N/O ratio of the hot plasma is consistent with that of the stellar wind, i.e., lower than the nebular N/O ratio, but this result is not conclusive.