Discovery of Extended X-Ray Emission from the Planetary Nebula NGC 7027 by the [ITAL]Chandra X-Ray Observatory[/ITAL

Abstract

We report the discovery of X-ray emission from NGC 7027, a prototypical object for the study of the formation and evolution of planetary nebulae. Observations with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-Ray Observatory show that the X-ray emission from NGC 7027 is extended and is bipolar in morphology. The ACIS spectrum displays strong emission from highly ionized Ne and weaker emission features, which we attribute to O, Mg, and Si. Model fits to this spectrum suggest a characteristic temperature TX ~ 3 × 106 K and an intrinsic (unabsorbed) X-ray luminosity of LX ~ 1.3 × 1032 ergs s-1. The intranebular absorption of X-ray emission is highly nonuniform, but the modeling indicates an average column density NH ~ 6 × 1021 cm-2, consistent with previous measurements of relatively large visual extinction within the nebula. We suggest that the X-ray emission from NGC 7027 is or was generated by a hitherto undetected fast wind from the central star of NGC 7027 or from a companion to this star. Chandra's detection of extended, high-temperature X-ray emission from BD +30°3639, NGC 6543, and now NGC 7027 suggests that such emission is a common feature of young planetary nebulae.