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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

Absolute UV fluxes from the Sun and late-type stars

C. Allende Prieto

McDonald Observatory

Univ. of Texas

not without help
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)
importance of the solar late type uv spectrum
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)
slide11
VALC

VALC: Vernazza, Avrett & Loeser 1973

slide12

T=5000 K

Pe= 3 dyn/cm2

Allende Prieto & Lambert 2000

the solar uv problem or not1
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)

differences
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
revisiting the problem
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

metal opacity
Metal opacity

Allende Prieto et al. 2003

recent developments
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
revisiting the problem1
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

where e come from
Where e- come from ...

CI FeI/MgI/SiI OI/SI

need to consider
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 …

slide27

and Si and possibly Ca

A seven-pipe problem!

revisiting the problem2
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

models
MODELS
  • Fully consistent 1D models (LTE for now: Tlusty code of Hubeny & Lanz)
  • NLTE line formation (Tlusty + models from OP/IP)
  • 3D model atmospheres
slide35
NLTE

Allende Prieto, Hubeny

& Lambert 2003

slide36
3D
  • New 3D radiative transfer code

(Koesterke et al. 2007)

  • Full opacities
  • Scattering
  • Multiple solar simulations
summary
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