High-resolution X-ray image of the hydrogen-deficient planetary nebula Abell 30

Abell 30 is the brighter of only two planetary nebulae that show extended X-ray emission. Our recent ROSAT high-resolution imager observation of A30 reveals a central source at a 4 σ level and emission knots at a 2 σ level. These emission features are within the same region as the H-deficient knots and filaments resolved in a previous HST WFPC2 [O III] image. The ROSAT position of the X-ray peak is offset by 2″.8 from the HST position of the central star of A30. Since the ROSAT pointing may be uncertain by up to 10″, we assume that the X-ray peak is aligned with the central star. The two brighter X-ray emission knots then become aligned with prominent [O III] features in the nebula. Ground-based echelle observations and HST WFPC2 images of A30 reveal a bipolar pair of knots and a clumpy expanding disk. The morphology and velocity structure of the bipolar knots and disk show evidence of the stellar wind ablating the knots and clumps. An efficient mixing of the shocked stellar wind and the ablated material is needed to produce the low plasma temperature, 4.5 × 10⁵ K, and the high electron density, ∼1000 cm^-3, derived from the observed X-ray flux and spectral distribution.