V605 Aql: The Older Twin of Sakurai's Object

Abstract

New optical spectra have been obtained with VLT/FORS2 of the final helium shell flash (FF) star, V605 Aql, which peaked in brightness in 1919. New models suggest that this star is experiencing a very late thermal pulse. The evolution to a cool luminous giant and then back to a compact hot star takes place in only a few years. V605 Aql, the central star of the Planetary Nebula (PN), A58, has evolved from T${}_{eff}\sim$5000 K in 1921 to $\sim$95,000 K today. There are indications that the new FF star, Sakurai's Object (V4334 Sgr), which appeared in 1996, is evolving along a similar path. The abundances of Sakurai's Object today and V605 Aql 80 years ago mimic the hydrogen deficient R Coronae Borealis (RCB) stars with 98% He and 1% C. The new spectra show that V605 Aql has stellar abundances similar to those seen in Wolf-Rayet [WC] central stars of PNe with ~55% He, and ~40% C. The stellar spectrum of V605 Aql can be seen even though the star is not directly detected. Therefore, we may be seeing the spectrum in light scattered around the edge of a thick torus of dust seen edge-on. In the present state of evolution of V605 Aql, we may be seeing the not too distant future of Sakurai's Object.

12 pages, 1 figure, ApJ Letters in press

Cited by in corpus (6)

• The hydrogen-deficient knot of the `born again' planetary nebula Abell 58 (V605 Aql)
• R Coronae Borealis stars in the Galactic Bulge discovered by EROS-2
• The onset of photoionization in Sakurai's Object (V4334 Sgr)
• The enigma of the oldest `nova': the central star and nebula of CK Vul
• A dense disk of dust around the born-again Sakurai's object
• Astrophysics in 2006