van Hoof, P. A. M. ; Kimeswenger, S. ; Van de Steene, G. C. ; Avison, A. ; Zijlstra, A. A. ; Guzman Ramirez, L. ; Herwig, F. ; Hajduk, M.

Invited talk presented at Hydrogen Deficient Stars 2018, Armagh, UK on 2018-09-13

Abstract: Born-again stars are central stars of planetary nebulae (PNCS) that have undergone a (very) late thermal pulse after they have left the AGB. Evolutionary models predict that around 10-20% of PNCS should undergo a (V)LTP, yet only a handful of born-again objects are known. Only two of these were seen undergoing the flash: V605 Aql in 1918 and V4334 Sgr (a.k.a. Sakurai's object) in 1996. In my review I will give an overview of the observations of these objects, focusing mainly on V4334 Sgr as this is by far the best observed example of a born-again star. The talk will cover both observations of the central star and the circumstellar material that was ejected in the (V)LTP event.