1. Tubingen, 17-21 September, 20071 Optical spectroscopy of the born- again Sakurai's object in 1996 Igor Savanov Simon Jeffery Don Pollacco Denis Shulyak and others

2. Tubingen, 17-21 September, 20072 The rapid evolution: The extraordinarily rapid evolution of the born-again giant Sakurai’s object following discovery in 1996 has been investigated in papers by Duerbeck et al., Shetrone & Keane, Asplund et al, Jeffery, Pollacco, Kipper & Klochkova, Pavlenko and others. The evolution was traced both in a continued cooling of the stellar surface and dramatic changes in chemical composition on a timescale of a mere few months. The abundance alterations are the results of the mixing and nuclear reactions which have ensued due to the final He-shell flash which occurred during the descent along the white dwarf cooling track. The observed changes in the H and Li abundances can be explained by ingestion and burning of the H-rich envelope and Li-production through the Cameron-Fowler mechanism. The rapidly increasing abundances of the light s-elements are consistent with current s-processing by neutrons released from the concomitantly produced 13C.

3. Tubingen, 17-21 September, 20073 What we want to know: Photospheric diagnostic from high and medium resolution spectrograms Tracing of the evolution on timescales months/weeks Circumstellar diagnostic

4. Tubingen, 17-21 September, 20074 New grid of models: Line-by-line opacity stellar model atmospheres D. Shulyak, V. Tsymbal T. Ryabchikova et al;A&A 428, 993–1000 (2004) T eff = 6000 (500) 8500 Log g=0.0 (0.5) 1.0 N(H)= 0.01,0.03,0.1,0.3 N(C)=0.003, 0.01,0.03,0.1

5. Tubingen, 17-21 September, 20075 |DATASET: |DATASET: 01.03.96 5960-7212 1.2 R=5000 JD=245 0144 19.03.96 5772-6987 1.2 R=5000 162 27.03.96 3606-7018 3.3 R=1500 170 31.03.96 3648-7003 3.3 R=1500 174 01.04.96 5893-7147 1.2 R=5000 175 01.04.96 6909-8184 1.2 R=5000 175 01.04.96 7891-9141 1.2 R=5000 175 02.04.96 5894-7143 1.2 R=5000 176 25.04.96 6144-6958 0.8 R=7500 199 25.04.96 6394-7203 0.8 R=7500 199 15.05.96 3848-5054 aat 0.04 219 15.05.96 3849-5054 aat 219 23.05.96 6024-7164 0.6 R=10000 227 31.05.96 3865-4663 0.8 wht R=5000 235 31.05.96 5776-7280 1.2 wht R=5000 235 06.06.96 5739-6822 0.5 R=10000 241 20.06.96 5879-6742 0.8 R=7500 255 01.07.96 5846-6619 0.7 R=7500 266 09.07.96 5880-6743 0.8 R=7500 274 24.07.96 5849-6621 0.7 R=7500 292 01.08.96 5878-6744 0.8 R=7500 297 17.08.96 5879-6742 0.8 R=7500 313 07.09.96 5696-6945 1.2 R=5000 334 26.09.96 5879-6744 0.8 R=7500 353 28.10.96 5875-6738 0.8 R=7500 385

6. Tubingen, 17-21 September, 20076 |DATASET: |DATASET: 05.05.96 MCDONALD *RAO R=30000 3700-10150 209 06.05.96 MCDONALD mentioned by Asplund 210 09.05.96 MCDONALD mentioned by Asplund R=60000 5720-7200 214 07.10.96 MCDONALD *RAO 364 20.04.96 CTIO Shetrone,Keane R=14000 3800-7500 S/N=100-200 194 25.04.96 CTIO Wallerstein R=12500 199 04.06.96 WHT Pollacco R=45000 3800-8000 S/N=70 239 03.05.96 5263-6955 low 15000 PFES 6 meter SAO Klochkova V. 207 01.05.96 25000 Lynx 205 04.07.96 25000 Lynx 269

7. Tubingen, 17-21 September, 20077 Optical spectroscopy in 1996:

8. Tubingen, 17-21 September, 20078 H line profiles : T=8000 K log g =0.5, Vt=7.5, H=0.01, C/He=0.1 AAT 15.05.1996

9. Tubingen, 17-21 September, 20079 H line profiles : T=8000 K log g =0.5, Vt=7.5, H=0.01, C/He=0.1 log ε(O)=9.3; log ε(N)=9.0

10. Tubingen, 17-21 September, 200710 Zr II lines: New and improved experimental oscillator strengths in Zr II and the solar abundance of zirconium, Ljung, G.; Nilsson, H.; Asplund, M.; Johansson, S. AA, 456, 2006, pp.1181-1185 Ljung, G.Nilsson, H.Asplund, M.Johansson, S. Ljung, G.Nilsson, H.Asplund, M.Johansson, S.

11. Tubingen, 17-21 September, 200711 Y II, Ba II. La II lines:

12. Tubingen, 17-21 September, 200712 Abundances:

13. Tubingen, 17-21 September, 200713 Ca II lines:

14. Tubingen, 17-21 September, 200714 Rapid evolution ? 09.05.96 07.10.96 15.05.96

15. Tubingen, 17-21 September, 200715 Our plans: We are compiling a library of optical spectra obtained during 1996 in order: - to ensure that the observed record of this extremely rare phenomenon remains accessible to future researchers and - to re-visit the question of its early evolution. This is particularly important for understanding the precise timing and magnitude of the dredge-up of material to the surface of the star following a late thermal pulse. We present preliminary results of a new analysis of some of these data. These include possibly the first direct evidence of dynamical behaviour in the expanding stellar envelope.