Brown Dwarf Science with VLST
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Transcript of Brown Dwarf Science with VLST
Brown Dwarf Science with VLST Outline: The Big
Questions Where we are
and how VLST would help...
John GizisPhysics and Astronomy
Brown Dwarf Science with VLSTFormation
Atmospheres
Brown Dwarf Science with VLSTFormationIMFBinarityDisks
Atmospheres
Brown Dwarf Science with VLSTFormationIMFBinarityDisks
AtmospheresEvolutionBeyond T dwarfsActivity
Brown Dwarf Science with VLST Brown
dwarfs below ~0.074Mfai
l to achieve stable nuclear burning.
Cool and fade steadily
Burrows et al. 1993, 1997
Brown Dwarf Science with VLST Brown
dwarfs below ~0.074Mfai
l to achieve stable nuclear burning.
Cool and fade steadily
Burrows et al. 1993, 1997
Brown Dwarf Science with VLST Brown
dwarfs below ~0.074Mfai
l to achieve stable nuclear burning.
Cool and fade steadily
Planets vs. brown dwarfs
Burrows et al. 2003
Brown Dwarf Science with VLST 2MASS and
SDSS find objects
Sequence to T8 or ~800K.
Vrba et al. 2004
L dwarf sequence Disappearance of
molecules as grains form.
Cloud deck ~1600K
Kirkpatrick et al. 1999
T dwarf sequence Classification in
near-IR. Cloud deck ~1600K
below photosphere.
Burgasser et al. 2003
T dwarf sequence Classification in
near-IR.
Burgasser et al. 2002
On beyond T with VLST?
Not really... Want large
sky area and mid-infrared.
Spitzer, JWST
WISE
Burrows et al. 2003
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
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
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
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
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
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.
ResolutionGizis et al. 2003
Open cluster T dwarfs
Star-formking regions: Probe to lowest masses.
Burrows et al. 1997
Open cluster T dwarfs
Star-formking regions: Probe to lowest masses.
UKIRT
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.
Low Metallicity/Halo Field Halo Brown
Dwarfs 2M0532+8346 An L subdwarf
Burgasser et al. 2003
Spectra Beyond T dwarfs
Liebert et al. 2002
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
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
Activity HST/STIS
can detect M8/M9 dwarfs
Need VLST for Le/Te dwarfs.
Also, for cluster late-M dwarfs.
Hawley & Johns-Krull 2003
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
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
Weather? Variability at
I band is few percent.
Can we show that it is due to clouds? Hotspots? Sunspots?
Hurt
Summary Very Large
Space Telescope
Needed for followup of expected discoveries.
Needed for more distant L/T dwarfsHurt