FUSE spectroscopy of cool PG1159 Stars Elke Reiff (IAAT) Klaus Werner, Thomas Rauch (IAAT) Jeff Kruk...
-
Upload
amberlynn-dickerson -
Category
Documents
-
view
218 -
download
0
description
Transcript of FUSE spectroscopy of cool PG1159 Stars Elke Reiff (IAAT) Klaus Werner, Thomas Rauch (IAAT) Jeff Kruk...
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 18th 2007
Observations
Observations obtained with FUSE• 905 – 1187 Å (R ≈ 10000 – 20000 ≈ 0.1Å)• 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 EB-V and NH
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
• PG1424+535 (110 kK, log g = 7.0)• PG1707+427 (85 kK, log g = 7.5)
• literature values for Teff 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 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
Static Models
Fe VII in PG1424+535
• Teff = 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 PG1707+427
• Teff = 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 PG1707+427
• Teff = 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 showstrong 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
Wind Models
Modelling of expanding stellar atmospheres• characteristic parameters Teff, 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 ModelsPrevious analyses investigated…
but spectra show also P Cygni profiles of…
Wind Models
Ne VII@ 973 Å
Wind Models
F VI@ 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