Formation and fate of the born-again planetary nebula HuBi 1

e present the first 3D radiation-hydrodynamic simulations on the formation and evolution of born-again planetary nebulae (PNe), with particular emphasis to the case of HuBi 1, the inside-out PN. We use the extensively tested GUACHO code to simulate the formation of HuBi 1 adopting mass-loss and stellar wind terminal velocity estimates obtained from observations presented by our group. We found that, if the inner shell of HuBi 1 was formed by an explosive very late thermal pulse (VLTP) ejecting material with velocities of ∼300 km s−1, the age of this structure is consistent with that of ≃200 yr derived from multi-epoch narrow-band imaging. Our simulations predict that, as a consequence of the dramatic reduction of the stellar wind velocity and photon ionizing flux during the VLTP, the velocity and pressure structure of the outer H-rich nebula are affected creating turbulent ionized structures surrounding the inner shell. These are indeed detected in Gran Telescopio Canarias MEGARA optical observations. Furthermore, we demonstrate that the current relatively low ionizing photon flux from the central star of HuBi 1 is not able to completely ionize the inner shell, which favours previous suggestions that its excitation is dominated by shocks. Our simulations suggest that the kinetic energy of the H-poor ejecta of HuBi 1 is at least 30 times that of the clumps and filaments in the evolved born-again PNe A 30 and A 78, making it a truly unique VLTP event. © 2021 The Author(s).
JAT thanks funding by Fundación Marcos Moshinsky (Mexico) and the Direcciónn General de Asuntos del Personal Académico (DGAPA) of the Universidad Nacional Autónoma de México (UNAM) project IA100720. VL gratefully acknowledges support from the CONACYT Research Fellowship program. BMM and MAG acknowledge support of the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU) grant PGC2018-102184-B-I00. AE acknowledges support from DGAPA-PAPIIT (UNAM) grant IN 109518. This work has made extensive use of NASA’s Astrophysics Data System.
With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.