Chandra observations of the planetary nebula IC 4593

The Advanced CCD Imaging Spectrometer (ACIS-S) camera on board the Chandra X-ray Observatory has been used to discover a hot bubble in the planetary nebula (PN) IC 4593, the most distant PN detected by Chandra so far. The data are used to study the distribution of the X-ray-emitting gas in IC 4593 and to estimate its physical properties. The hot bubble has a radius of similar to 2 arcsec and is found to be confined inside the optically bright innermost cavity of IC 4593. The X-ray emission is mostly consistent with that of an optically thin plasma with temperature kT approximate to 0.15 keV (or T-X approximate to 1.7 x 10(6) K), electron density n(e) approximate to 15 cm(-3) , and intrinsic X-ray luminosity in the 0.3-1.5 keV energy range L-X = 3.4 x 10(30) erg s(-1). A careful analysis of the distribution of hard (E >0.8 keV) photons in IC4593 suggests the presence of X-ray emission from a point source likely associated with its central star (CSPN). If this was the case, its estimated X-ray luminosity would be L-X,(CSPN) = 7 x 10(29) erg s(-1), fulfilling the log(L-X, (CSPN)/L-bol) approximate to -7 relation for self-shocking winds in hot stars. The X-ray detection of the CSPN helps explain the presence of high-ionization species detected in the ultraviolet spectra as predicted by stellar atmosphere models.