Brown Dwarf Theory

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Brown Dwarf Theory
(Adam Burrows)
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Outline

• Major Themes
• Brown Dwarfs Stepping stones to the planets
• Structure and Evolution
• Equation of State
• Composition and Opacities Thermochemistry,
  Atmospheres
• Basics of T and L Dwarf theory
• Y Dwarfs
• Alkali Metals
• The Future

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Brown Dwarf Exotica

• Deuterium Burning
• Metallic H/He cores
• Molecular Atmospheres
• H2, H2O, CH4, CO, N2, NH3, FeH, CrH, Na, K,
  silicates, ..
• L lt 6 x 10-5 LO
• R 0.1 RO for all masses
• 300 K lt Te lt 1800 K
• g 1 to 300 gs
• Infrared
• Masses 5-75 MJ

• L and T dwarfs!
• Silicate clouds (L dwarfs)
• Depleted atmospheres (rainout) in T dwarfs
• Broad alkali metal lines
• Mass function still rising at main-sequence edge
• J, H, K fluxes much higher that blackbody
• T dwarfs get bluer with decreasing Te (in the
  IR)
• J, Z fluxes increase near L/T transition

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Theory Program for ModelingExtrasolar Giant
Planets (EGPs) and Brown Dwarfs

• Opacity and Molecular spectroscopy calculations
  (Quantum chemistry) e.g., ro-vibrational
  transitions
• Ab-initio calculations for Na-D, K I, FeH, CrH,
  TiH
• Equation of State of H2 and He, etc.
• Atmospheres and Abundances Thermochemistry (1600
  species)
• Cloud modeling (silicates, Fe, H2O, NH3),
  Meteorology
• Radiative transfer and atmosphere techniques 1D
  and 2D
• Evolution, Spectra, Chemistry, and Colors of
  isolated and irradiated substellar-mass objects
  (SMOs) and planetary structure studies
• Theory of T and L dwarfs massive giant planets
  
• (Collaborators Burrows, Hubbard, Hubeny,
  Sudarsky, Sharp, Milsom, Lunine, Li, Fortney,
  Cooper, Budaj, Volobuyev)

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Luminosity vs. Age vs. Mass
Planets?
Burrows et al. 1997 Burrows et al. 2001
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M
Jupiter?
Burrows et al. 2001
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Equation of State of H2 / He Mixtures

• Liquid Metal Intermediate Coulomb Regime

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Burrows et al. 2001
EOS of H2
Coulomb interactions vs. electron degeneracy
Wigner and Huntington (1935)
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Radius-Mass Relation
OGLE-TR-122 (VLM) Data Pont et al. 2005
Jupiter
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Radius vs. Mass for BDs Theory vs. Obs.
Isochrones
Burgasser, Burrows, Kirkpatrick 06
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Chemical Composition

• (and Clouds)

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Burrows et al. 2001
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CH4/CO
NH3/N2
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M Dwarfs
L Dwarfs
T Dwarfs
Jupiter
Burrows et al. 2001
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Condensates in EGP and Brown Dwarf Atmospheres
Fe, silicates, H2 O, NH3
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Fe, silicate, H2 O, NH3 , .. clouds
Na2 S, KCl hazes
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Molecular and Atomic Opacities

• (critical tools)

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CO, H2O, and CH4 Opacities
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Molecular Opacities
Burrows et al. 2001
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L and T Dwarfs
(Adam Burrows)
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L Dwarfs
T Dwarfs
Reid et al. 2000
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T Dwarfs
M Dwarfs
TiO/VO
T dwarfs Refractory-depleted
H2O
L dwarfs Refractory-rich
Burrows et al. 2001
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Binaries?
L to T transition
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Absolute Spectral Fits to L Dwarfs
Clouds!?
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Absolute Spectral Fits to T Dwarfs
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Spitzer/IRAC mid-IR Spectral Data
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Non-Irradiated Giant Planets Y Dwarfs

• (free-floating, wide orbit)

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Isolated EGPs and Y Dwarfs
Clouds
Burrows, Sudarsky, and Lunine 2003
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Isolated BDs/EGPs
No reflection
Burrows et al. 2003
JWST WISE
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Alkali Metals
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K I
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K I
Na-D
Burgasser et al. 2001
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Burrows and Volobuyev 2003
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The Color of a Brown (L) Dwarf
K I
Na-D
Reid et al. 2000
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Magenta Dwarfs
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Irradiated Brown Dwarfs
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Spitzer ST
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JWST