TY  - JOUR
A1  - Guerrero, Martin A.
A1  - Fang, Xuan
A1  - Miller Bertolami, Marcelo Miguel
A1  - Ramos-Larios, Gerardo
A1  - Todt, Helge Tobias
A1  - Alarie, Alexandre
A1  - Sabin, Laurence
A1  - Miranda, Luis F.
A1  - Morisset, Christophe
A1  - Kehrig, Carolina
A1  - Zavala, Saul A.
T1  - The inside-out planetary nebula around a born-again star
JF  - Nature Astronomy
N2  - 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 descendant of a low-mass star (≃1.1 M⊙) that has experienced a ‘born-again’ event1 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 object2. Coming from a solar-mass progenitor, HuBi 1 represents a potential end-state for our Sun.
KW  - Astronomy and astrophysics
KW  - Astronomy and planetary science
KW  - Interstellar medium
KW  - Stars
KW  - Stellar evolution
Y1  - 2018
U6  - https://doi.org/10.1038/s41550-018-0551-8
SN  - 2397-3366
VL  - 2
IS  - 10
SP  - 784
EP  - 789
PB  - Nature Publ. Group
CY  - London
ER  -