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Astrophysics > Galaxy Astrophysics

Title: Rebirth of X-ray Emission from the Born-Again Planetary Nebula A 30

Authors: M. A. Guerrero, N. Ruiz, W.-R. Hamann, Y.-H. Chu, H. Todt, D. Schoenberner, L. Oskinova, R. A. Gruendl, M. Steffen, W. P. Blair, J. A. Toalá
(Submitted on 20 Feb 2012 (v1), last revised 19 Jun 2012 (this version, v2))
Abstract: The planetary nebula (PN) A30 is believed to have undergone a very late thermal pulse resulting in the ejection of knots of hydrogen-poor material. Using HST images we have detected the angular expansion of these knots and derived an age of 850+280-150 yr. To investigate the spectral and spatial properties of the soft X-ray emission detected by ROSAT, we have obtained Chandra and XMM-Newton observations of A30. The X-ray emission from A30 can be separated into two components: a point-source at the central star and diffuse emission associated with the hydrogen-poor knots and the cloverleaf structure inside the nebular shell. To help us assess the role of the current stellar wind in powering this X-ray emission, we have determined the stellar parameters of the central star of A 30 using a non-LTE model fit to its optical and UV spectrum. The spatial distribution and spectral properties of the diffuse X-ray emission is suggestive that it is generated by the post-born-again and present fast stellar winds interacting with the hydrogen-poor ejecta of the born-again event. This emission can be attributed to shock-heated plasma, as the hydrogen-poor knots are ablated by the stellar winds, under which circumstances the efficient mass-loading of the present fast stellar wind raises its density and damps its velocity to produce the observed diffuse soft X-rays. Charge transfer reactions between the ions of the stellar winds and material of the born-again ejecta has also been considered as a possible mechanism for the production of diffuse X-ray emission, and upper limits on the expected X-ray production by this mechanism have been derived. The origin of the X-ray emission from the central star of A 30 is puzzling: shocks in the present fast stellar wind and photospheric emission can be ruled out, while the development of a new, compact hot bubble confining the fast stellar wind seems implausible.
Comments: 29 pages, 11 figures, 4 tables; accepted for publication by ApJ
Subjects: Galaxy Astrophysics (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
DOI: 10.1016/j.icarus.2012.09.025
Cite as: arXiv:1202.4463 [astro-ph.GA]
  (or arXiv:1202.4463v2 [astro-ph.GA] for this version)

Submission history

From: Martin A. Guerrero [view email]
[v1] Mon, 20 Feb 2012 21:03:34 GMT (3424kb)
[v2] Tue, 19 Jun 2012 09:46:43 GMT (4582kb)
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