Freshly ionized matter around the final Helium shell flash object V4334 Sgr (Sakurai's object)

Abstract

We report on the discovery of recently ionized hydrogen-deficient gas in the immediate circumstellar environment of the final helium shell flash star V4334 Sgr (Sakurai's object). On spectra obtained with FORS2 multi-object spectroscopy we have found spatially extended (about 2") emission from [N II], [O I], [O II] and very faint Halpha and [S II]. In the [N II] (ll6548,83) lines we have identified two components located at velocities -350 +/-50 and +200 +/-50 km/s, relative to V4334 Sgr itself. The full width of the [N II] l6583 feature at zero intensity corresponds to a velocity spread of about 1500 km/s. Based on the available data it is not possible to conclusively determine the mechanism of ionization. Both photo-ionization, from a rapidly evolving central star, and shock excitation, as the result of the collision of the fast ouflows with slower circumstellar matter, could account for the observed lines. The central star is still hidden behind strong dust absorption, since only a faint highly reddened continuum is apparent in the spectra. Theory states that it will become hotter and will retrace its post-asymptotic giant branch evolution towards the planetary nebula domain. Our detection of the ionized ejecta from the very late helium shell flash marks the beginning of a new phase in this star's amazingly rapid evolution.

11 pages, 2 figures. Accepted by ApJL

References in corpus (3)

• The evolutionary time scale of Sakurai's object: A test of convection theory?
• Freshly ionized matter around the final Helium shell flash object V4334 Sgr (Sakurai's object)
• Models of infrared spectra of Sakurai's Object (V4334 Sgr) in 1997

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• A dense disk of dust around the born-again Sakurai's object
• Expansion of hydrogen-poor knots in the born-again planetary nebulae A30 and A78
• Evolution of the 1919 Ejecta of V605 Aquilae
• Freshly ionized matter around the final Helium shell flash object V4334 Sgr (Sakurai's object)
• On the discovery of an enormous ionized halo around the hot DO white dwarf PG1034+001
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• The sub-millimetre evolution of V4334 Sgr (Sakurai's Object)
• Non-thermal radio emission in Sakurai's Object
• Common envelope evolution in born-again planetary nebulae -- Shaping the H-deficient ejecta of A30
• The very fast evolution of Sakurai's object
• A primer on the formation and evolution of hydrogen deficient Central Stars of Planetary Nebulæ and Related Objects