Abstract

We present the results of Chandra X-Ray Observatory observations of the planetary nebulae (PNs) NGC 40 and Hen 2-99. Both PNs feature late-type Wolf-Rayet central stars that are currently driving fast (!1000 km s^-1), massive winds into denser, slow-moving (~10 kms^-1)material ejected during recently terminated asymptotic giant branch (AGB) evolutionary phases. Hence, these observations provide key tests of models of wind-wind interactions in PNs. In NGC 40, we detect faint, diffuse X-ray emission distributed within a partial annulus that lies nested within a ~40" diameter ring of nebulosity observed in optical and near-infrared images. Hen 2-99 is not detected. The inferred X-ray temperature (Tx ~10^6 K) and luminosity (Lx ~2 x10^30 ergs s^-1) of NGC 40 are the lowest measured thus far for any PN displaying diffuse X-ray emission. These results, combined with the ringlike morphology of the X-ray emission from NGC 40, suggest that its X-ray emission arises from a ‘‘hot bubble’’ that is highly evolved and is generated by a shocked, quasi-spherical fast wind from the central star, as opposed to AGB or post-AGB jet activity. In contrast, the lack of detectable X-ray emission from Hen 2-99 suggests that this PN has yet to enter a phase of strong wind-wind shocks.

Publication Date

12-10-2005

Comments

Also archived in: arXiv :astro-ph/0508346 v1 16 Aug 2005 This research was supported by NASA through Chandra award number GO4–5169X issued to Rochester Institute of Technology by the Chandra X-ray Observatory Center, which is operated by Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8–03060. O.D. is grateful to Janet Jeppson Asimov for financial support.ISSN:1538-4365 Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type

Article

Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)

Campus

RIT – Main Campus

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