Modelling of spectra and model atmospheres of evolved stars

1. (A talk from the parallel world) Yakiv V.Pavlenko Main astronomical observatory 27 Sabolotnoho, Kyiv, Ukraine www.mao.kiev.ua/staff/yp Modelling of spectra and model atmospheres of evolved stars

4. Collaborators Carlos Abia (UG) Greg Harries (UCL) Yakovina Larisa(MAO) Kaminsky Bogdan (MAO) Hugh Jones (UH) Nye Evans(Keele) Hilmar Duerbeck(OU) Sveta Zhukovska (MAO) Thomas Geballe (UKIRT)

5. Stars of interest: Hydrogen-rich stars --- M-giants --- C-giants --- V838 Mon Hydrogen poor stars --- R CrB --- Sakurai’s object

6. Outline Model atmospheres and fits to SEDs Isotopic ratios (12C/13C) Abundances (Lithium abundances)

7. PROCEDURE Model atmospheres SAM12 (ATLAS12) 1D, Convection + radiation, LTE, No sinks and sources of energy Opacity sampling for line opacity Synthetic spectra WITA 1D, LTE, Voigt function for lines VCS theory for H lines SEDs

8. OPACITIES: C/O < 1, Opacity sources: VO, TiO; H2O, CO Methane C/O > 1 CN, CO, CH, C2,HCN, C3, --- [H]?? --- isotopes!

9. Problems: • Opacities (missed continuum absorption in the blue, line lists (both atomic and molecular), isotops, • chemical abundances and equilibrium, • 3-D convection, • sphericity effects, • the dust, • stellar winds.

10. Astronomy often progresses amoeba- like: the advance in one pseudopod may not move the animal very far, but permits other parts to advance in their turn and can reveal portions of the organism that are in danger of being left behind. V.Trimble, R.A.Bell, Q.Jl.R.astr.Soc.(1981),22, 361-379

11. C-giants

12. New grid 1-D model atmosphes Teff= 3400 – 2000 log g = 1. 0 metallicity -4, -3.5, -3, -2.5, -2, -1.5, -1, -0.5, 0, 1, 1.5, 2 [C/O] = 0.003, 0.007, 0.01, 0.02, 0.03 New HCN & NHC

15. Sakurai's object (V4334 Sgr)

21. V838 Mon

24. “...Given the web of interconnected uncertainties and errors presented here, one is initially tempted to give up on stellar atmospheres completely and turn to something simple like cosmology.” V.Trimble & R.A, Bell:

25. The quality of fits to observed spectra depends on: OBSERVED SPECTRA (slopes, de-redenning, resolution) Model atmospheres Input data for the synthetic spectra

26. Fine analysis of stellar spectra(Abundance analysis) Input: a) Model atmospheres b) Line lists c) Partition functons, dissociation constants... d) chemical bounds

27. Lithium in C-stars

30. Problems of Li abundance determination in C-giants Line lists (CN, C2, ...) Heavy elements (lists, abundances) 3D NLTE Veiling

31. CO bands(12C/13C isotopic ratio)

32. 12C/13C in globular clusters M71: [Fe/H] = -0.7 M5: [Fe/H] = -1.2 M13: [Fe/H]= -1.4 M3: [Fe/H] = -1.6

33. Fits to observed spectra

37. Pavlenko, Yakiv V., Jones, Hugh R. A., Longmore, Andrew J., 2003, 'Carbon abundances and 12C/13C from globular cluster giants.' MNRAS, 345, 311-324.

38. 12C/13C in Sakurai’s object Main problems to be solved: --- dust veiling --- Model atmosphere with peculiar abundances

42. Conclusions Model atmospheres and theoretical spectra must be obtained in the framework of self-consistent approach. Iterative procefure of abundances determination should be implemented. Different spectral ranges should be used. Input data used in modelling must be improved.

43. V.Trimble,R.A.Bell: ... But this is a snare and a delusion, as the more esoteric branches of astrophysics have been built up on the assumption that we understand things like stellar masses, evolution (YP:and abundances:). ... Thus if the fundation is shaky, so is superstructure.

44. / to be continued...