Results 151 to 160 of about 6,433 (179)
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Nuclei of planetary nebulae and white dwarf envelopes
Astrophysics and Space Science, 1973Upper bounds to the masses of He envelopes of white dwarfs are derived by examining the maximum He envelope that a nucleus of a planetary nebulae can have consistent with observation.
A. Kovetz, G. Shaviv
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Evolutionary status of WR-type planetary nebula nuclei
Astrophysics and Space Science, 1996In this paper we review the evolutionary paths that lead to the different types of planetary nebulae nuclei, including hydrogen and helium-burning central stars. Starting from the empirical definition of WR central stars, based on stellar spectra, we examine the theoretical work produced to account for the observed configurations.
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An O VIII Sequence for Planetary Nebula Nuclei
Publications of the Astronomical Society of the Pacific, 1996The detection of O VIII emission lines in ultraviolet and optical spectra of high-excitation planetary nebula central stars suggests an "O VIII Sequence" for these object. Emission lines of O VII are also detected. Seven out of ten central stars for these planetaries are known to be nonradial g-mode pulsators. The stars form a narrow strip when plotted
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[WR] nuclei of planetary nebulae: Inferences from statistical studies of the nebulae
Astrophysics and Space Science, 1996There are about 50 galactic planetary nebulae know to have [WR] type nuclei. We have compared their nebular properties with those of the other planetary nebulae in the Galaxy. We have found that the nebular morphological types are similarly distributed in the two groups. Bipolar nebulae constitute only 20% of the total in each group.
Sławomir K. Górny, Grazyna Stasińska
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The Evolution of the Nuclei of Planetary Nebulae
Publications of the Astronomical Society of Australia, 1972In the past decade, planetary nebulae have assumed considerable importance in elucidating our understanding of the final stages of stellar evolution at low mass. This began with the work of Shklovsky, O’Dell and Seaton, who showed not only that the nuclei of these nebulae were among the hottest stellar objects, but also that they evolved on a track in ...
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Galactic planetary nebulae and evolution of their nuclei
Astrophysics, 1980The galactic system of planetary nebulae is investigated using previously constructed distance scale and kinematics data. A strong effect of observational selection is established, which has the consequence that with increasing distance, ever brighter and younger objects are observed. More accurate determinations of the spatial and surface densities of
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Nonradial g-Mode Instabilities in Planetary Nebula Nuclei
1987We report preliminary results of fully nonadiabatic gravity mode pulsation calculations for evolutionary models of planetary nebula nuclei (PNNs) with active nuclear burning shells. For hot PNNs at luminosities below ~2000 L⊙, we find instabilities driven by the nuclear burning shell(s) via the very potent e-mechanism.
Steven D. Kawaler +3 more
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Binary planetary nebulae nuclei towards the Galactic bulge
2015Binarity has been hypothesised to play an important, if not ubiquitous, role in the formation of planetary nebulae (PNe). Yet there remains a severe paucity of known binary central stars required to test the binary hypothesis and to place strong constraints on the physics of the common-envelope (CE) phase of binary stellar evolution.
Moffat, Anthony F J +4 more
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Carbon dust in the evolved born-again planetary nebulae A 30 and A 78
Monthly Notices of the Royal Astronomical Society, 2021Jesus A Toala +2 more
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