T Tauri Stars Can YSOs Effect Your Horoscope

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T Tauri StarsCan YSOs Effect Your Horoscope?

• Presenter Paul Edmon
• 12-05-05
• Astronomy 4001

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Overview

• Young Stellar Objects
• Classical T Tauri Stars
• Weak Line T Tauri Stars
• Summary

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Young Stellar Objects (YSO)

• Objects contracting out of a molecular cloud
• Pre-Main Sequence (PMS)
• Go from Contraction to Convection to Radiation
• Time scales to reach the Zero Age Main Sequence
  (ZAMS) vary depending on Mass of Star

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YSO Collapse Times

• Low Mass YSOs M
• Legend
• Green Isochrones
• Red Convection
• Blue Radiation
• Birthline Start of Convection
• ZAMS Zero Age Main Sequence

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YSO Evolution

• A
• YSO I Protostar
• Gravitational Collapse
• Beginning of Spin-up
• B
• YSO II Classical T Tauri Star (CTTS)
• Disk Accretion
• Jets

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YSO Evolution

• C
• YSO III Weak Line T Tauri Star (WTTS)
• Disintegration of Disk
• Fusion
• D
• ZAMS
• Fusion
• Possible Planets

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Classical T Tauri Stars (CTTS)

• Optically Visible, but usually faint due to
  obscuration
• W? (Ha) 10Å
• Excess IR and sub-millimeter emission
• Hydrogen Balmer and Ca II H and K in emission
• Spectral Type later than F

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CTTS Morphology

• Disk and Jet
• Associated with Herbig-Haro (HH) Objects

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CTTS Theory

• Angular Momentum Conservation
• Gravitational Collapse of Cloud
• Creation of Accretion Disk (100 AU)
• Jets
• Perpendicular to Accretion Disk
• Probably Magneto-hydrodynamic (MHD) in origin
• Can extend for parsecs
• Energy Transport due to Convection

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CTTS Theory

• Protostar is a Plasma
• Since the plasma obeys the Frozen in Condition
  the magnetic field gets wrapped up due to
  convection
• Creates large cool spots on the surface much like
  Sun Spots
• Also creates large X-Ray flares where the plasma
  is caught up in the magnetic field with
  temperatures about 107 K

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Weak Line T Tauri Stars (WTTS)

• Visible in the Optical with little obscuration
• W? (Ha)
• Blackbody with red excess
• Powerful Stellar Winds
• Otherwise Like CTTS

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WTTS Theory

• Energy Transport by Radiation
• Initiation of Hydrogen Fusion
• Final Decent onto ZAMS
• Stellar Winds push out remaining disk and
  disrupts the jets
• Convection region is smaller
• Smaller dark spots and X-Ray Flares
• Much more like the Sun but not quite stable yet

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Summary

• T Tauri Stars are a subclass of YSOs
• CTTS mark the change from Gravitational Collapse
  to Internal Convection of the Protostar
• WTTS mark the change from Convection Transport to
  Radiation Transport

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Summary

• WTTS also mark when Hydrogen Fusion become
  dominate in a Protostar
• Better understanding of the disk and jets are
  needed to fully understand T Tauri Stars
• T Tauri Stars give insight to how our Sun evolved
  on to the Main Sequence

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Sources

• Bertrout, C. T Tauri Stars Wild as Dust,
  Annual Reviews of Astronomy and Astrophysics, 27,
  pg. 351-395, 1989
• Neuhaüser, R. Low-Mass Pre-Main Sequence Stars
  and Their X-Ray Emission, Science, 276, pg.
  1363-1370, 1997
• Space Telescope Science Institute
  http//www.stsci.edu