Hot Young Brown Dwarfs

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Hot Young Brown Dwarfs

• Kai Cai
• Oct. 17, 2003

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Brown Dwarfs
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Definition Characteristics
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A recent discovery

• High angular resolution imaging low-res.
  spectroscopy of VLT
• ? Indi B is a close binary!
• T1 and T6 dwarfs, separation 2.65AU

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Formation theories

• Typical Jeans mass 1M?
• Collapse of low-mass cores denser
• Padoan Nordlund (2003) turbulent
  fragmentation
• Failed stars ejected embryos
• Reipurth Clarke (2001)
• Bate et al. (2002) SPH simulation
• Sterzik Durisen (2003) orbit integrations

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Formation observations
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Disks of Young Brown Dwarfs

• H? broad asymmetric ? accretion
• mid-IR excess K L 0.2
• Disk fraction 40-60, 1/3
• Decrease in the fraction of accreting BDs
• with increasing age
• Conclusion BDs share a common origin with
  low-mass stars

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Disks of Young Brown Dwarfs

• Sub-mm/mm emission cold dust
• Mass of the circumstellar 1MJ, a few of BD
• Overall SED (0.3-1000?m)
• Flat disk geometry fits well
• Flared disk with inner rim puffed up
• Overall shape similar to T Tau disks

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Formation Mechanisms

• ? Ongoing debate?
• Key issues 1) Disk lifetime?
• 2) When did dynamical interactions occur?
• How efficient?
• More observations to the BDs in transition age?
• Look for free-floating young BDs?

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BDs in Young Clusters

• IC 348 youngest
• Cha I
• Taurus Upper Sco 3-5Myr
• ? Orion 5Myr
• TW Hydrae Association 10Myr
• ? Oph
• IC 2391 35Myr

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Ongoing Efforts

• Evolutionary Tracks/Isochrones
• Luminosity Functions
• IMFs