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NLTE Model Atmospheres for Super-Soft X- ray Sources

NLTE Model Atmospheres for Super-Soft X- ray Sources. Thomas Rauch. Overview. “Born-Again” Post-AGB Stars Spectral Analysis of Hot, Compact Stars. Interior of AGB Stars. Post-AGB Evolution. Iben 1984, ApJ 277, 333. “Born-Again” Post-AGB Stars. AGB Final Thermal Pulse ( AFTP )

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NLTE Model Atmospheres for Super-Soft X- ray Sources

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  1. NLTE Model Atmospheresfor Super-Soft X-raySources Thomas Rauch

  2. Overview • “Born-Again” Post-AGB Stars • Spectral Analysis of Hot, Compact Stars

  3. Interior of AGB Stars

  4. Post-AGB Evolution Iben 1984, ApJ 277, 333

  5. “Born-Again” Post-AGB Stars • AGB Final Thermal Pulse (AFTP) • MH  10-2 Mʘ,MHe  10-2 Mʘ •  40% H left on surface • Late Thermal Pulse (LTP) • MH  10-4 Mʘ,MHe  10-2 Mʘ • 1% H left on surface (not detectable) • Very Late Thermal Pulse (VLTP) • MH  10-4 Mʘ,MHe  10-2 Mʘ • no H burning shell, H burned at bottom of He burning shell • no H left

  6. Interior of AGB Stars Direct view on intershell matter allows to conclude on details in nuclear processes and mixing processes in AGB stars  Test for stellar-evolution models

  7. Model Atmospheres • LTE (Local Thermodynamical Equilibrium) • dimension of region in LTE > mean free path of photons • occupation numbers from Boltzmann distribution + Saha equation • S  B • NLTE • occupation numbers ni in stationary equilibrium

  8. Equation System mean intensity frequency points  0 equations + NF equations = NF statistical equations NLTE levels (NL levels) = NL hydrostatic equilibrium 1 particle conservation 1 radiative equilibrium 1 NF + NL + 3 equations

  9. Classical Models NF = 65 NL = 18  86 equations numerical accuracy! (32 bit computers …) • before 1986! levels line transitions ion NLTE LTE RBB H I 5 11 6 H II 1 He I 5 11 0 He II 6 16 0 He III 1 18 48 6

  10.  Iteration  good for

  11. Approximate * Operator iteration step i: convergence: advantage: local operator!  reduction of equation system! - transfer equations - rate equations

  12. Accelerated Lambda Iteration • “Classical” models • 1969 H models, complete linearization • Auer & Mihalas 1969, ApJ 156, 157 • 1972 H+He models (Auer & Mihalas) • 1972 H+He + average light element (Mihalas) • “Beyond classical” models • 1986 H+He+C, ALI method (Werner) • 1990 H - Fe, multi-frequency/multi gray (Anderson) • 1991 H+He+C+N+O+Si (Werner, Dreizler, Rauch) • 1993 impact of iron-group elements (Hubeny & Lanz)

  13. Model Atoms • levels treated in NLTE energies ? • levels treated in LTE energies ? • radiative + collisional transistions • RBB/CBB oscillator strengths ? • RBF/CBF ionization cross sections ? • RFF cross sections ? • line broadening ?

  14. NLTE Model Atmospheres C IV doublet “optical” RBB 5  6, 6  8 C III singlet + triplet all stars with spectral type B or earlier regarded as a domain of specialists high computational times atomic data

  15. More Model Ions … Fe VII simplified Hauschildt diagram

  16. PG 1159-035 Heber & Hunger 1991, German Research, Reports of the DFG 1st appropriate NLTE models available!

  17. Beyond Classical Models • 1986 H+He+C, ALI method (Werner) • 1990 H - Fe, multi-frequency/multi gray (Anderson) • 1991 H+He+C+N+O+Si (Werner, Dreizler, Rauch) • 1993 impact of iron-group elements (Hubeny & Lanz) • 1993 iron-group elements (Dreizler & Werner) • 1997“light-metal” (H-Ca) models (Rauch) • 2003 H-Ni models (Rauch) • “fully metal-line blanketed” • LTE: Kurucz 1979

  18. TMAP • Tübingen Model-Atmosphere Package • http://astro.uni-tuebingen.de/~rauch/TMAP/TMAP.html • Werner et al., 2003, ASPC, 288, 31 • Rauch & Deetjen, 2003, ASPC, 288, 103 • NLTE • plane-parallel or spherical • homogeneous • hydrostatic equilibrium, diffusion • radiative equilibrium

  19. Fluorine • First discovery of fluorine in hot post-AGB stars: • F VI1139.50 Å • 14N(α,)18F(β+)18O(p,α)15N(α,)19F • F abundance in PG 1159 stars up to 200  solar • Werner, Rauch & Kruk 2005 • F intershell abundance in evolutionary models is right • Lugaro et al. 2004

  20. Neon  Ne VII 3644Å first identified 1994(Werner & Rauch) Iben & Tutukov 1985, ApJS, 58, 661 • 14N(α,n)18F(β+)18O(α,γ)22Ne • intershell abundance of 2% by mass (11  solar) expected

  21. FUSE: Ne VII Ne VII 973.3Å, one of strongest lines in FUSE spectra first identified 2004 (Werner et al.) Herald, Bianchi, & Hillier, 2005 Ne VII973Å – the assumed C III 977Å P Cygni feature

  22. VLT: Ne VII Newly discovered Ne VII multiplet in VLT spectra (Werner et al. 2004) Improvement of atomic data of highly excited Ne VII lines  NIST (Kramida et al. 2006)

  23. Ne VIII new data by Kramida & Buchet-Poulizac 2006 precise determination of Teff in hottest stars, here DO KPD0005+5106 before: Teff = 120 000 K now: Teff = 200 000 K

  24. Iron FUSE spectral range covers strongest Fe VII lines. Up to now, FUSE spectra from four PG1159 stars (K 1-16, PG 1159-035, NGC 7094, A 78) with sufficiently high S/N analyzed. What is expected? reduced (sub-solar) intershell Fe abundance, by n-captures - Reduced to what extent?

  25. Iron-Deficiency in LTP Stars • CSPN Abell 78 • Teff = 110 000 K • log g = 5.5 (cm/sec2) • Fe abundance variation • 1/10 and 1/100 solar • no iron lines detectable in FUSE spectra of all four examined PG1159 stars: • Fe deficiency of 1-2 dex • very strong Fe depletion in intershell • Miksa et al. 2002, Jahn et al. 2007

  26. S-Process: Fe-Depletion test by Herwig et al. 1999 just qualitative

  27. Trans-Iron Elements • CSPN NGC 7094 • Teff = 110 000 K • log g = 5.7 (cm/sec2) • [Fe] = -1.6 • [Ni] = 0 • AFTP star • H = 0.36 (by mass) • He = 0.43 • C = 0.21 • Fe/H ratio should be solar = 1.6 ·10-3 (by mass) • NGC 7094: 3.9 ·10-5 Ziegler et al. 2009, A&A, in prep.

  28. Spectroscopy of PG1159 Stars • He, C, N, O, Ne, Mg, F, Si, Ar are in line with predictions from evolutionary models • Fe depletion is surprisingly large (up to 2 dex sub-solar) • Ni is not overabundant • P is roughly solar, but models predict strong enhancement • S is expected to stay solar, but large depletions (up to 2 dex) • for a review, see Werner & Herwig 2006, PASP, 118, 183

  29. Spectroscopy of LS V +46°21 • exciting star of Sh 2-216 • closest PN known, d = 130pc • apparent diameter 1.6° • LS V +46°21 about 0.2 radii off centre • mild interaction with ISM • thin disk orbit of low inclination and eccentricity • Kerber et al. 2004 • FUSE: 67.6 ksec in 2003/2004, R 0.05 Å • STIS: 5.5 ksec in 2000, R 0.06 Å Hα + [O III] Dean Salman www.deansalman.com

  30. Spectroscopy of LS V +46°21 • HHeCNOFMgSiPSAr + CaScTiVCrMnFeCoNi • IrOnIc • Rauch & Deetjen 2003 • 686 NLTE levels • 2417 individual lines • 9 million iron-group lines • Kurucz 1996 • Rauch et al. 2007, A&A, 470, 317 Teff= 95 000 K log g = 6.9

  31. LS V +46°21 Photospheric abundances exhibit interplay of gravitational settling and radiative levitation Photospheric abundances in agreement with diffusion predictions (Chayer et al. 1995)

  32. FUSE spectrum of PG1159-035 and model fit incl. ISM model Jahn et al. 2007, A&A, 462, 281

  33. H1504+65 Teff = 200 000 K log g = 8

  34. Magnesium in H 1504+65

  35. H 1504+65: CHANDRA Spectrum Werner et al. 2004

  36. H 1504+65: Iron group

  37. KPD 0005+5106 Teff = 200 000 K instead of Teff = 120 000 K

  38. Nova V 4743 Sgr • outburst Sep 20, 2002, mV = 5 • Mar 2003: brightest super-soft source in the sky • CHANDRA spectrum • C V, C VI, N VI, N VII, O VII absorptions • Teff 1 – 2 MK (Ness et al. 2003) • XMM-RGS spectrum (Apr 4, 2003) • Teff 610 kK (Rauch, Werner & Orio 2005)

  39. SEDs for Extremely Hot Stars

  40. V 4743 Sgr

  41. Teff Determination: N VI / N VII IonizationEquilibrium

  42. Effective Temperature of Nova V 4743 Sgr after Burst

  43. EXO 0748-676 (LMXB) • discovery of gravitationally redshifted photosphericabsorption lines of Fe XXV, Fe XXVI, O VIII in burst spectra • Cottam, Paerels & Mendez 2002 • letter to NATURE, 420, p. 51

  44. no fit at z = 0.35

  45. much better fit at z = 0.24 ?

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