Sakurai's object: a [WC] star in a new bipolar nebula after a VLTP

TL;DR

This paper reports on the evolving spectrum of Sakurai's object, revealing shock-induced changes and the formation of a new bipolar nebula following a Very Late Thermal Pulse, with signs of emerging stellar wind features.

Contribution

It provides new observational evidence of spectral evolution and nebula formation in a VLTP object, highlighting shock effects and ionization processes.

Findings

Emergence of C II and C III emission lines typical of [WC] stars

Increase in [O III] and [S III] lines suggests onset of photoionisation

Formation of a new bipolar nebula inside the old nebula

Abstract

Optical spectra of the Very Late Thermal Pulse (VLTP) object V4334 Sgr have shown a rapidly changing spectrum resulting from shocks in the outflow, which created a new bipolar nebula inside the old nebula. We see C II and C III emission lines emerging typical of a [WC 11-10]-type star. The strong increase of [O III] and [S III] emission lines indicate the possible onset of photoionisation in the new ejecta.