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Absolute UV fluxes from the Sun and late-type stars

Absolute UV fluxes from the Sun and late-type stars. C. Allende Prieto McDonald Observatory Univ. of Texas. Not without help. Analisis: D. L. Lambert, I. Ramirez (Texas) Model atmospheres, radiative transfer: I. Hubeny (Arizona), L. Koesterke (Texas) 3D models: M. Asplund (Australia)

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Absolute UV fluxes from the Sun and late-type stars

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  1. Absolute UV fluxes from the Sun and late-type stars C. Allende Prieto McDonald Observatory Univ. of Texas

  2. Not without help... • Analisis: D. L. Lambert, I. Ramirez (Texas) • Model atmospheres, radiative transfer: I. Hubeny (Arizona), L. Koesterke (Texas) • 3D models: M. Asplund (Australia) • Atomic data: M. A. Bautista (Venezuela), S. Nahar (Ohio), T. Lanz (Maryland)

  3. Importance of the Solar/Late-type UV spectrum • Life on Earth • Astrophysical importance: rich in information • Late-type stars contribute mass (and light) to distant galaxies (z: UV shifts to optical or IR)

  4. The Solar UV problem ... or not • Chromosphere

  5. In the red ...

  6. EIT 171 nm

  7. EIT 195 nm

  8. EIT 284 nm

  9. EIT 304 nm

  10. Ca II K line

  11. VALC VALC: Vernazza, Avrett & Loeser 1973

  12. T=5000 K Pe= 3 dyn/cm2 Allende Prieto & Lambert 2000

  13. Rosseland Optical Depth

  14. The Solar UV problem ... or not • Chromosphere • Missing opacity? Houtgast & Namba (1968), Labs & Neckel (1968), Matshushima (1968), Chmielewski, Brault & Mueller (1975)... Kurucz (1992) Bell et al. (1994)

  15. Balachandran, Bell & Bautista 2001

  16. Allende Prieto, Hubeny & Lambert 2003

  17. Differences... • Abundances: log epsilon(Mg)=7.44 – 7.58 log epsilon(Fe) =7.55 – 7.50 • Fe I opacity Bautista -- hydrog. • Lyman alpha! • Equation of state: consistency or lack thereof • Molecules

  18. Revisiting the problem • OPACITIES lines: atoms, molecules continua – OP (up to Ca), IP (Fe) • Equation of state Ne consistent with abundances and chemical equilibrium • MODELS Consistency with abundances NLTE 3D

  19. Metal opacity Allende Prieto et al. 2003

  20. Opacities

  21. Recent developments • Adoption of the FeI model from Bautista (1997) • and the FeII model from Nahar (1995), Nahar & Pradhan (2005) • Consistent with previous models: TOPBASE, Tlusty formats

  22. Revisiting the problem • OPACITIES lines: atoms, molecules continua – OP (up to Ca), IP (Fe and Fe-peak) • Equation of state Ne consistent with abundances and chemical equilibrium • MODELS Consistency with abundances NLTE 3D

  23. Where e- come from ... CI FeI/MgI/SiI OI/SI

  24. Need to consider • Continuum opacity: FeI, MgI (AlI, SiI if λ < 200 nm) • Electrons: FeI, MgI, SiI • Molecules: C, O • And of course, H (or He/H) But …We don’t know the solar abundances well enough …

  25. and Si and possibly Ca A seven-pipe problem!

  26. FeI hydrogenic to IP

  27. Comparing with Kurucz (1993)

  28. HOWEVER ...

  29. Asplund, Grevesse, & Sauval 2005

  30. A solution...?

  31. Revisiting the problem • OPACITIES lines: atoms, molecules continua – OP (up to Ca), IP (Fe and Fe-peak) • Equation of state Ne consistent with abundances and chemical equilibrium • MODELS Consistency with abundances NLTE 3D

  32. MODELS • Fully consistent 1D models (LTE for now: Tlusty code of Hubeny & Lanz) • NLTE line formation (Tlusty + models from OP/IP) • 3D model atmospheres

  33. NLTE Allende Prieto, Hubeny & Lambert 2003

  34. 3D • New 3D radiative transfer code (Koesterke et al. 2007) • Full opacities • Scattering • Multiple solar simulations

  35. Summary • With 1D/LTE Kurucz model, modern (OP IP) opacities, and AGS05 abundances, we still have a solar UV problem • But reasonable variations in the abundances and the equation of state are likely to solve it • Consistency is necessary: abundance variations must be fed back to the equation of state, the electron density and the atmospheric structure • 3D effects and NLTE effects need to be explored

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