T Tauri Stars: An Overview

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T Tauri Stars An Overview

• Colette Salyk
• Ge132

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What is a T Tauri star?

• 1st Answer Observational
• Hydrogen Balmer and Ca II H and K emission
• Often emission of Fe I
• Forbidden O I and S II emission
• Strong Li absorption
• IR -gt sub-mm excess
• UV excess
• Found in dusty regions- proper motions correlated
• Off main sequence
• Sometimes associated with disks and/or outflows

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What is a T Tauri star?

• 2nd Answer Theoretical
• Low-mass (0.2-2 M? ) young (PMS) star
• Class II
• Often accompanied by disk of gas and dust
• Active (star/disk interactions, fast rotation)
• Sometimes releasing mass via polar outflows

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IR Excess

• Near-IR hot inner disk dust and gas
• mid-IR -gt sub-mm dusty disk emission
• Solar accretional energy

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H? emission

• n3-gtn2 transition
• ? 6562.8 Å
• Requires high energy photons, close to star
  (also seen in solar chromosphere)
• Used to model accretion
• Asymmetric shape
• Doppler broadening gt100 km/s (supersonic)

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Strong Li I Absorption

• ? 6707.76 Å 2P3/2 -gt2S1/2
• ? 6707.91 Å 2P1/2 -gt2S1/2
• Li fragile, destroyed when in contact with high
  temperatures at base of convecting region of
  stars, so strong Li young
• In TTSs, lognLi 3 similar to meteorites (in
  sun, lognLi 1 lognH12)

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Forbidden O I S II emission

• Very low emission probabilities-gtlow density
  environment
• Probe outer regions of polar jets
• Doppler broadened -gthigh speeds
• Blueshifted (red part partially hidden)

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Ca II H K, Fe I emission

• Ca II H
• ? 3968.5 Å
• 2S1/2 lt-2P1/2
• Ca II K
• ? 3933.7 Å
• 2S1/2 lt-2P3/2
• Fe I
• ? 4062.4 Å 3P1 lt-3S1
• ? 4132.1 Å 3F2 lt- 3F3
• Probably due to resonant fluorescence
• All similar to solar chromosphere, but actually
  due to extended atmosphere and star/disk
  interactions

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Implications / The Future

• Initial Mass Function ( N(M) )
• Effect of environment on formation
• Mass of disk correlations? (environment, mass of
  parent star, age)
• Young Star/Disk Interactions
• Magnetic fields
• Accretion
• Mass loss
• Evolution timescales
• How long do outflows/disks last?
• (How long do planets have to form?)