1. FUSE spectroscopy of cool PG1159 Stars Elke Reiff (IAAT) Klaus Werner, Thomas Rauch (IAAT) Jeff Kruk (JHU Baltimore) Lars Koesterke (University of Texas) Hydrogen-Deficient Stars, Tübingen, September 18 th 2007

2. Observations Observations obtained with FUSE 905 – 1187 Å ( R ≈ 10000 – 20000 ≈ 0.1 Å) Rowland spectrograph: 4 gratings and 2 detectors, 2 coatings (Lithium-Fluoride, Silicon-Carbide) Data reduction: standard Calfuse Pipeline, done by J.W. Kruk shifted to rest wavelength of photospheric lines corrections for interstellar reddening E B-V and N H

3. Static Models Modelling of the stellar atmosphere NLTE model atmospheres, using TMAP basic assumptions:  plane-parallel geometry, homogeneous structure  hydrostatic equilibrium (matter is at rest)  radiative equilibrium (no convection)  statistical equilibrium / rate equations (NLTE)  particle and charge conservation

4. Static Models Detailed analysis of 2 „cool“ PG1159 stars PG1424+535 (110 kK, log g = 7.0) PG1707+427 (85 kK, log g = 7.5) literature values for T eff and log g literature values for abundances models comprise He, C, N, O, Ne analysis of light metals F, Si, S, P analysis of Fe and Ni upper abundance limits

5. Static Models Beyond light metals: including iron and nickel too many levels and lines for numerical treatment concept: combine energy levels to few „superlevels“ lines are combined to transitions between bands POS lines: observed; precisely known wavelengths LIN lines: observed + theoretically predicted  IrOnIc (Iron Opacity Interface)

6. Static Models Iron group elements in PG1159 stars strong depletion of iron found, e.g. in the prototype PG 1159-035 (Jahn et al. 2007) iron depletion might be due to transformation into heavier elements by s-process neutron capture upper limit for nickel abundance still uncertain  POS lines for the final synthetic spectrum  upper limits for Fe and Ni abundance determined

7. Static Models Fe VII in PG1424+535 T eff = 110kK, log g 7.0 POS lines of Fe VII used upper limit of the iron abundance is 0.1 x solar (compared to 0.01 x solar and solar abundance)  Fe ≲ 0.1 x solar abund.

8. Static Models Fe VI in PG1707+427 T eff = 85kK, log g 7.5 POS lines of Fe VI used upper limit of the iron abundance is about solar (compared to 0.1 x solar and 10 x solar)  Fe ≲ solar abundance

9. Static Models Ni VI in PG1707+427 T eff = 85kK, log g 7.5 POS lines of Ni VI used upper limit of the nickel abundance is about solar (compared to 0.1 x solar and 10 x solar)  Ni ≲ solar abundance

10. Summary Analyses with static stellar atmospheres upper limits for Fe and Ni abundance determined  depletion for Fe observable  but no enrichment of Ni detectable  origin of Fe-depletion not yet understood

11. Wind Models Six objects in the sample of PG1159 stars show strong P Cygni wind profiles in their spectra: RXJ 2117.1+3412 (170kK, log g 6.0) NGC 246 (150kK, log g 5.7) K 1-16 (140kK, log g 6.4) Abell 78 (110kK, log g 5.5) NGC 7094 / Abell 43 (110 kK, log g 5.7)  Static models do not reproduce P Cygni profiles  Analysis with wind models required

12. Wind Models Modelling of expanding stellar atmospheres characteristic parameters  T eff, log g, L  R , M   mass loss rate M  terminal velocity v ∞ and velocity field v(r) using wind-code of Lars Koesterke  spherically expanding atmosphere (1D)  homogeneous and stationary wind  wind models include H, He, C, N, O, Ne, F ·

13. Wind Models Previous analyses investigated… but spectra show also P Cygni profiles of…

14. Wind Models Ne VII @ 973 Å

15. Wind Models F VI @ 1139 Å

16. Summary Analyses with static stellar atmospheres upper limits for Fe and Ni abundance determined  depletion for Fe observable  but no enrichment of Ni detectable  origin of Fe-depletion not yet understood Analyses with expanding stellar atmospheres P Cygni wind profiles for trace elements Ne and F  determine and confirm abundances  see following talk by Marc Ziegler

18. Static Models Modelling of the stellar atmosphere NLTE model atmospheres, using TMAP basic assumptions:  plane-parallel geometry, homogeneous structure  hydrostatic equilibrium (matter is at rest)  radiative equilibrium (no convection)  statistical equilibrium / rate equations (NLTE)  particle and charge conservation solve radiative transfer equation