Orsola de Marco, Deptartment of Physics and Astronomy, University
College London, Gower Street, London, WC1E 6BT, UK
The evolutionary connection between the born-again phenomenon and central stars of planetary nebulae (PN) with a Wolf-Rayet (WR) spectral type, is not a straight forward one. So much so, that it might actually be misleading to theorise to much about it. However, it is important to keep in mind a few observations, as well as theories, which might clarify the physical (rather than evolutionary) connection between the two phenomena.
In this talk I will present all the cases where a [WR] central star has a clear connection to the born-again scenario, emphasising how the physics of the stellar atmosphere, which reveals itself though the WR spectrum, can arise in different circumstances.
I will touch upon objects such as V 605 Aql, a 1917 born-again star, known to have developed, after a brief period as an R Coronae Borealis (RCB) star, a WR spectrum; I will also describe the `old' born-again PNe A 30 and A 78, with their almost-[WR] spectrum and their H-deficient PNe. I will very briefly touch upon the love triangle between [WC] central stars, born-again and RCB stars (which will be amply described by Geoff Clayton at this meeting), to stress how sometimes similar physics takes place in objects which do not necessarily have an evolutionary connection. I will finally conclude with some lines of work which might help in the solution of some of the problems surrounding [WC] stars and the born-again phenomenon.