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Brown Dwarf Science with VLST

Brown Dwarf Science with VLST. John Gizis Physics and Astronomy. Outline: The Big Questions Where we are and how VLST would help. Brown Dwarf Science with VLST. Formation Atmospheres. Brown Dwarf Science with VLST. Formation IMF Binarity Disks Atmospheres.

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Brown Dwarf Science with VLST

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  1. Brown Dwarf Science with VLST John Gizis Physics and Astronomy • Outline: • The Big Questions • Where we are and how VLST would help...

  2. Brown Dwarf Science with VLST Formation Atmospheres

  3. Brown Dwarf Science with VLST Formation IMF Binarity Disks Atmospheres

  4. Brown Dwarf Science with VLST Formation IMF Binarity Disks Atmospheres Evolution Beyond T dwarfs Activity

  5. Brown Dwarf Science with VLST • Brown dwarfs below ~0.074MM fail to achieve stable nuclear burning. • Cool and fade steadily Burrows et al. 1993, 1997

  6. Brown Dwarf Science with VLST • Brown dwarfs below ~0.074MM fail to achieve stable nuclear burning. • Cool and fade steadily Burrows et al. 1993, 1997

  7. Brown Dwarf Science with VLST • Brown dwarfs below ~0.074MM fail to achieve stable nuclear burning. • Cool and fade steadily • Planets vs. brown dwarfs Burrows et al. 2003

  8. Brown Dwarf Science with VLST • 2MASS and SDSS find objects • Sequence to T8 or ~800K. Vrba et al. 2004

  9. L dwarf sequence • Disappearance of molecules as grains form. • Cloud deck ~1600K Kirkpatrick et al. 1999

  10. T dwarf sequence • Classification in near-IR. • Cloud deck ~1600K below photosphere. Burgasser et al. 2003

  11. T dwarf sequence • Classification in near-IR. Burgasser et al. 2002

  12. On beyond T with VLST? • Not really... • Want large sky area and mid-infrared. • Spitzer, JWST • WISE Burrows et al. 2003

  13. But followup will require large telescopes... • We will have many cool, very-low-mass brown dwarfs by any VLST launch date Burrows et al. 2003

  14. But followup will require large telescopes... • We will have many cool, very-low-mass brown dwarfs by any VLST launch date Burrows et al. 2003

  15. Images • 20% of L and T dwarfs are resolved by HST • Separations 2-10AU • P2 = a3/MT • Current periods are ~30 years. • We can expect that a VLST could find the binaries at 0.1 AU -- <1 yr period. • These could include very-low-mass companions. Gizis et al. 2003

  16. For 5 MJ field brown dwarfs, a separation of 5 AU will have a period >100 years. • Need a VLST both to get enough photons and to resolve them (at one micron). • A VLST would get to separations of .1 AU and periods < 1yr. • Also need VLST to resolve open cluster and Taurus brown dwarfs. Gizis et al. 2003

  17. For 5 MJ field brown dwarfs, a separation of 5 AU will have a period >100 years. • Need a VLST both to get enough photons and to resolve them (at one micron). • A VLST would get to separations of .1 AU and periods < 1yr. • Also need VLST to resolve open cluster and Taurus brown dwarfs. Gizis et al. 2003

  18. For 5 MJ field brown dwarfs, a separation of 5 AU will have a period >100 years. • Need a VLST both to get enough photons and to resolve them (at one micron). • A VLST would get to separations of .1 AU and periods < 1yr. • Also need VLST to resolve open cluster and Taurus brown dwarfs. • Resolution Gizis et al. 2003

  19. Open cluster T dwarfs • Star-formking regions: Probe to lowest masses. Burrows et al. 1997

  20. Open cluster T dwarfs • Star-formking regions: Probe to lowest masses. UKIRT

  21. Low Metallicity/Halo • Imaging at ~1 micron should detect brown dwarfs in globular clusters. • Need to reach T~800K to be interesting. • Resolution and field of view.

  22. Low Metallicity/Halo • Field Halo Brown Dwarfs • 2M0532+8346 • An L subdwarf Burgasser et al. 2003

  23. Spectra • Beyond T dwarfs Liebert et al. 2002

  24. Activity • Gizis et al. 2000 found that activity declines sharply after M6. • But, flares are common. • Burgasser et al. 2003 find some Ha at 10-18 erg/sec/cm2 Liebert et al. 2002

  25. Activity • Gizis et al. 2000 found that activity declines sharply after M6. • But, flares are common. • Burgasser et al. 2003 find some Ha at 10-18 erg/sec/cm2 Liebert et al. 2002

  26. Activity • HST/STIS can detect M8/M9 dwarfs • Need VLST for Le/Te dwarfs. • Also, for cluster late-M dwarfs. Hawley & Johns-Krull 2003

  27. Formation • What about accreting brown dwarfs/planets • Detection of emission lines in T dwarfs in star-forming regions. Gizis 2002; r Oph BD from Luhman

  28. Resolution? • Field brown dwarfs have v sin i ~ 5-80 km/s • Width of emission lines • HDO: 1% variations? • Lithium in distant clusters Gizis 2002; r Oph BD from Luhman

  29. Weather? • Variability at I band is few percent. • Can we show that it is due to clouds? Hotspots? Sunspots? Hurt

  30. Summary • Very Large Space Telescope • Needed for followup of expected discoveries. • Needed for more distant L/T dwarfs Hurt

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