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

Observations Observations obtained with FUSE 905 – 1187 Å ( R ≈ – ≈ 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

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

Static Models Detailed analysis of 2 „cool“ PG1159 stars PG (110 kK, log g = 7.0) PG (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

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)

Static Models Iron group elements in PG1159 stars strong depletion of iron found, e.g. in the prototype PG (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

Static Models Fe VII in PG 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.

Static Models Fe VI in PG 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

Static Models Ni VI in PG 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

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

Wind Models Six objects in the sample of PG1159 stars show strong P Cygni wind profiles in their spectra: RXJ (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

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 ·

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

Wind Models Ne 973 Å

Wind Models F 1139 Å

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

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