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A cosmic abundance standard

A cosmic abundance standard. from massive stars in the Solar Neighborhood. Fernanda Nieva. Norbert Przybilla (Bamberg-Erlangen) & Keith Butler (LMU). Cosmic abundance standard input for any model that requires initial or local elemental abundances: massive star evolution yields

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A cosmic abundance standard

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  1. A cosmic abundance standard from massive stars in the Solar Neighborhood Fernanda Nieva Norbert Przybilla (Bamberg-Erlangen) & Keith Butler (LMU)

  2. Cosmic abundance standard input for any model that requires initial or local elemental abundances: • massive star evolution • yields • supernovae • Galactic chemical evolution models • … Massive stars: a better option than solar-type stars

  3. Main Sequence Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 OB stars: cooler O & hotter B SN Young  age ~ 107 yrs Massive  M ~ 9-20 Msun Hot  Teff ~ 20-35 x104 K Luminous  L~104-105 Lsun •  radiative envelope • thin atmosphere (1D) Well-understood atmospheric structure absolute (physical) chemical composition (independently from solar values) • in contrast to cool stars: • no convective envelope (3D)  no chromosphere (heating) • in contrast to • hotter stars/supergiants: • no strong mass loss & winds (clumping... :-)

  4. Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 OB stars: in spiral arms, in star-forming regions, in Solar Neighbourhood Spatial & temporal information on chemical abundances short lived  birth place & present day (c.f. the Sun: a foreigner in the Solar Neighborhood)

  5. Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 OB stars: ideal tracers for chemical abundances at present day “locally“ from the Solar Neighborhood to nearby galaxies - current generation of telescopes OB stars: have much more simpler atmospheres than those of solar-type or cooler stars  But:their spectral synthesis and analysis has been subject to several unnacounted systematic effects in the past decades

  6. old NLTE: factor 10! LTE+NLTE: factor 40! Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 Present-day carbon abundance in the Solar Neighborhood: a long-standing problem... Young (OB) stars carbon No explanation from stellar -galactochemical evolution Carbon: the only problem..? No: abundances of other elements turned out to have large spread in the solar vicinity as well... (??)

  7. Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 • Our contribution: • Improving the spectral modeling (NLTE) • Improving the spectral analysis (self consistent) • Better observed spectra • Investigation of all possible systematic effects involved in chemical abundance determinations Hands into black boxes… All lines have to be reproduced simultaneously High resolution and very high S/N

  8. Example 1 Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 Reducing... -0.8 dex ! C II l4267 Ǻ very sensitive to (R-matrix) photoionization cross-sections C II l5145 Ǻnot sensitive to non-LTE effects Nieva & Przybilla (2008, A&A)

  9. Example 2 approximations (standard) vs. ab-initio (our) Also highly sensitive to collisional ionization only approximations: several orders of magnitude Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 Also: sensitivity to collisional excitation cross-sections Nieva & Przybilla (2008, A&A)

  10. Reducing... Example 3 ~+0.4 dex! ~ +1.1 dex! ~ -0.4 dex! Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 DTeff : -2000 K Dlog g: +0.2 dex Dx: +5 km s-1 DTeff : up to 4000/5000 K (~15%) from literature !! Nieva & Przybilla (2008, A&A)

  11. In agreement with SED’s (UV to near-IR): Data: IUE fluxes + Johnson & 2Mass photometry New self-consistent parameter determination: multiple ionization equilibria (independent model atoms & all possible lines in optical) Hotter stars:H, He I/II, C II/III/IV, Si III/IV, Ne I/II Cooler stars:H, C II/III, Si II/III/IV, O I/II, Ne I/II, Fe II/III Nieva & Przybilla (2008,A&A) Przybilla, Nieva & Butler (2008,ApJL) Nieva & Przybilla (2006, ApJL) In agreement with high-resolution near-IR (.98-4 mm) H, He I/II & C II/III Nieva et al. (2009)

  12. Near-IR optical Simultaneous fits to most measurable H/He lines Visual H Balmer H Paschen Data: FOCES, Calar Alto, Spain He I He I K-Band Data: Subaru, Hawaii He II Nieva & Przybilla (2007) Data: FEROS, ESO HR 3055

  13. optical Fits to C lines Data: FEROS, ESO C II Precise quantitative analysis All lines have very similar abundances low 1s-uncertainties C II/III/IV ionization equilibrium C III C IV t Sco Nieva & Przybilla (2008)

  14. NIR Helium Near-IR spectroscopy of OB stars Nieva et al. (2009) PREDICTIONS Hydrogen Telluric lines H lines  Teff & log g He lines  Teff & e(He) HeI/II ioniz. equil. Teff & log g B1.5 III

  15. NIR H lines  Teff & log g He lines  Teff & e(He) He I/II ioniz. equil. Teff & log g CII/III ioniz. equil. Teff & log g Near-IR spectroscopy of OB stars Nieva et al. (2009) PREDICTIONS Model: so far NLTE populations from visual ! Still no best fits from grid interpolations Monnet et al. ESO Messenger (2009)

  16. . Nieva & Przybilla (2008, A&A) Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 Present-day carbon abundance in the Solar Neighborhood:solving a long-standing problem... Young (OB) stars 15 sources of systematic errors were identified (besides atomic data) our work: ~10% old NLTE: factor 10! LTE+NLTE: factor 40! Unprecedented reduction of systematic errors in atmospheric parameters & input atomic data

  17. A cosmic abundance standard from massive stars in the Solar Neighborhood:absolute values Przybilla, Nieva & Butler (2008,ApJL) Recommended mass fractions: ≠ 0.020!

  18. Teff~ 31000 K Teff~ 27000 K Nieva & Przybilla (2008, A&A) Teff~ 21000 K Fernanda Nieva (MPA) Cosmic Abundance Standard Bonn, 05.06.2009 Non-LTE vs. LTE (final model atom + final parameters)

  19. Hybrid non-LTE approach: OK for OB Main Sequence stars (Nieva & Przybilla 2007) Non-LTE line formation Classical model atmospheresplan-parallel, hidrostatic & radiative equilibrium, LTE • Level populations: DETAIL • Formal solution: SURFACE (Giddings, 1981; Butler & Giddings 1985; updated by K. Butler, LMU) • Model atoms radiative transfer & statistical equilibrium H (Przybilla & Butler 2004) He I/II (Przybilla 2005) C II/III/IV (Nieva & Przybilla 2006, 2008) O, N, Mg, Al, Ne, Fe & others (Munich Observatory + N. Przybilla + K. Butler)

  20. Hybrid non-LTE approach Nieva & Przybilla (2007) • LTE atmospheres • + • NLTE line-formation • equivalent • full NLTE calculations • advantages: • - comprehensive • model atoms • - much faster • tailored • modelling

  21. Similar results for He, N, O Ne, Mg, Si, Fe So far O, Mg & Si confirmed by Firnstein (2006):BA-supergiants in Solar Neighb. Przybilla et al. (2006):BA-supergiants in Solar Neighb. Simon-Diaz (2009):B-stars in Orion OB assoc. Nieva et al. (in prep.):more OB-stars in Solar Neighb.

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