tubingen, 17-21 september, 20071 optical spectroscopy of the born- again sakurai's object in...

Tubingen, 17-21 September, 2007 1

Optical spectroscopy of the born-Optical spectroscopy of the born-again Sakurai's object in 1996again Sakurai's object in 1996

Igor SavanovSimon JefferyDon PollaccoDenis Shulyak

and others


The rapid evolution: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.


What we want to know:What we want to know:

Photospheric diagnostic from high and medium resolution spectrograms

Tracing of the evolution on timescales months/weeks Circumstellar diagnostic


New grid of models:New grid of models:

Line-by-line opacity stellar model atmospheres D. Shulyak, V. TsymbalT. Ryabchikova et al;A&A 428, 993–1000 (2004)

T eff = 6000 (500) 8500Log g=0.0 (0.5) 1.0N(H)= 0.01,0.03,0.1,0.3N(C)=0.003, 0.01,0.03,0.1


||DATASET: DATASET: 01.03.96 5960-7212 1.2 R=5000 JD=245 014419.03.96 5772-6987 1.2 R=5000 16227.03.96 3606-7018 3.3 R=1500 17031.03.96 3648-7003 3.3 R=1500 17401.04.96 5893-7147 1.2 R=5000 17501.04.96 6909-8184 1.2 R=5000 175 01.04.96 7891-9141 1.2 R=5000 17502.04.96 5894-7143 1.2 R=5000 17625.04.96 6144-6958 0.8 R=7500 19925.04.96 6394-7203 0.8 R=7500 19915.05.96 3848-5054 aat 0.04 21915.05.96 3849-5054 aat 21923.05.96 6024-7164 0.6 R=10000 22731.05.96 3865-4663 0.8 wht R=5000 23531.05.96 5776-7280 1.2 wht R=5000 23506.06.96 5739-6822 0.5 R=10000 24120.06.96 5879-6742 0.8 R=7500 25501.07.96 5846-6619 0.7 R=7500 266 09.07.96 5880-6743 0.8 R=7500 27424.07.96 5849-6621 0.7 R=7500 29201.08.96 5878-6744 0.8 R=7500 29717.08.96 5879-6742 0.8 R=7500 31307.09.96 5696-6945 1.2 R=5000 33426.09.96 5879-6744 0.8 R=7500 35328.10.96 5875-6738 0.8 R=7500 385


||DATASET: DATASET:

05.05.96 MCDONALD *RAO R=30000 3700-10150 20906.05.96 MCDONALD mentioned by Asplund 21009.05.96 MCDONALD mentioned by Asplund R=60000 5720-7200 21407.10.96 MCDONALD *RAO 364

20.04.96 CTIO Shetrone,Keane R=14000 3800-7500 S/N=100-200 19425.04.96 CTIO Wallerstein R=12500 19904.06.96 WHT Pollacco R=45000 3800-8000 S/N=70 239

03.05.96 5263-6955 low 15000 PFES 6 meter SAO Klochkova V. 20701.05.96 25000 Lynx 20504.07.96 25000 Lynx 269


Optical spectroscopy in 1996:Optical spectroscopy in 1996:


H line profiles : H line profiles : T=8000 K log g =0.5, Vt=7.5 , H=0.01, C/He=0.1T=8000 K log g =0.5, Vt=7.5 , H=0.01, C/He=0.1

AAT 15.05.1996


H line profiles : H line profiles : T=8000 K log g =0.5, Vt=7.5 , H=0.01, C/He=0.1T=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


Zr II lines: Zr II lines: New and improved experimental oscillator strengths in Zr II and New and improved experimental oscillator strengths in Zr II and the solar abundance of zirconiumthe solar abundance of zirconium,,Ljung, G.Ljung, G.; ; Nilsson, H.Nilsson, H.; ; Asplund, M.Asplund, M.; ; Johansson, S.Johansson, S. AAAA, 456, 2006, pp.1181-1185 , 456, 2006, pp.1181-1185


Y II, Ba II. La II lines:Y II, Ba II. La II lines:


Abundances:Abundances:


Ca II lines:Ca II lines:


Rapid evolution ?Rapid evolution ?

09.05.96

07.10.9615.05.96


Our plans: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.

tubingen, 17-21 september, 20071 optical spectroscopy of the born- again sakurai's object in...

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