Discovery of a Fast Expanding Shell in the Inside-out Born-Again Planetary Nebula HuBi 1 Through High-Dispersion Integral Field Spectroscopy

TL;DR

This study uses high-resolution spectroscopy and imaging to reveal a fast-expanding shell in the born-again planetary nebula HuBi 1, supporting the late thermal pulse ejection scenario and showing a shell-like structure unlike other similar nebulae.

Contribution

First high-dispersion integral field spectroscopy analysis of HuBi 1 revealing a shell-like ejecta structure and its expansion properties.

Findings

Ejecta ejected approximately 200 years ago.

Ejecta expanding at about 300 km/s.

Shell-like morphology contrasts with other born-again PNe.

Abstract

HuBi 1 has been proposed to be member of the rare class of born-again planetary nebulae (PNe), i.e., its central star experienced a very late thermal pulse and ejected highly-processed material at high speeds inside the old hydrogen-rich PN. In this letter we present GTC MEGARA integral field spectroscopic observations of the innermost regions of HuBi 1 at high spectral resolution $\simeq16$ km s$^{-1}$ and multi-epoch sub-arcsec images obtained $\simeq 12$ yr apart. The analysis of these data indicates that the inner regions of HuBi 1 were ejected $\simeq200$ yr ago and expand at velocities $\simeq300$ km s$^{-1}$, in excellent agreement with the born-again scenario. The unprecedented tomographic capabilities of the GTC MEGARA high-dispersion observations used here reveal that the ejecta in HuBi 1 has a shell-like structure, in contrast to the disrupted disk and jet morphology of the ejecta in other born-again PNe.