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