The inside-out planetary nebula around a born-again star

Abstract

Planetary nebulae are ionized clouds of gas formed by the hydrogen-rich envelopes of low- and intermediate-mass stars ejected at late evolutionary stages. The strong UV flux from their central stars causes a highly stratified ionization structure, with species of higher ionization potential closer to the star. Here we report on the exceptional case of HuBi 1, a double-shell planetary nebula whose inner shell presents emission from low-ionization species close to the star and emission from high-ionization species farther away. Spectral analysis demonstrates that the inner shell of HuBi 1 is excited by shocks, whereas its outer shell is recombining. The anomalous excitation of these shells can be traced to its low-temperature [WC10] central star whose optical brightness has declined continuously by 10 magnitudes in a period of 46 years. Evolutionary models reveal that this star is the descendent of a low-mass star ($\simeq$1.1 $M_{\odot }$) that has experienced a born-again event whose ejecta shock-excite the inner shell. HuBi 1 represents the missing link in the formation of metal-rich central stars of planetary nebulae from low-mass progenitors, offering unique insight regarding the future evolution of the born-again Sakurai's object. Coming from a solar-mass progenitor, HuBi 1 represents a potential end-state for our Sun.

arXiv comment21 pages, 3 figures, 6 supplementary figures, 1 supplementary table, published in Nature Astronomy

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Cited by in corpus (17)

• Catalogue of central stars of planetary nebulae: Expanded edition
• Abell 30 -- A Binary Central Star Among the Born-Again Planetary Nebulae
• Carbon dust in the evolved born-again planetary nebulae A30 and A78
• Planetary nebulae with Wolf-Rayet-type central stars -- I. The case of the high-excitation NGC 2371
• Hidden IR structures in NGC 40: signpost of an ancient born-again event
• Asteroseismic signatures of the helium-core flash
• Discovery of a Fast Expanding Shell in the Inside-out Born-Again Planetary Nebula HuBi 1 Through High-Dispersion Integral Field Spectroscopy
• The Initial-Final Mass Relation for Hydrogen-Deficient White Dwarfs
• Chemistry and physical properties of the born-again planetary nebula HuBi 1
• The Decline and Fall of the Youngest Planetary Nebula
• Formation and fate of the born-again planetary nebula HuBi 1
• Non-thermal radio emission in Sakurai's Object
• Common envelope evolution in born-again planetary nebulae -- Shaping the H-deficient ejecta of A30
• Spectral variability of the born-again ejecta in A 58
• Twenty years of observations of PM 1-188: Its chemical abundances and extraordinary kinematics
• A primer on the formation and evolution of hydrogen deficient Central Stars of Planetary Nebulæ and Related Objects
• Discovery of Extended Structures around Two Evolved Planetary Nebulae M 2-55 and Abell 2