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Spectroscopy of ultra-cool dwarfs Brown dwarfs come of age. Fuerteventura. May 20-24, 2013 Víctor J. S. Béjar (IAC)
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Spectroscopy of ultra-cool dwarfs
Brown dwarfs come of age. Fuerteventura. May 20-24, 2013
Víctor J. S. Béjar(IAC)
• Ultra-cool definition
• L, T and Y spectral types
• Substellarity: Li Test
• Low gravity ultra-cool dwarfs
• Low metallicity ultra-cool sub-dwarfs
• Extrasolar planets and L,T dwarfs
• Final remarks
Outline
Ultra-cool dwarf definition
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
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Kirkpatrick et al. 1997
Early discoveries of ultra-cool dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
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• Up to 1995, 20 dwarfs (≥M7) were known
Kirkpatrick et al. 1995
Early discoveries of L dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
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•1988: Becklin & Zuckerman found GD165 B (>=M10)
•1993 fist spectrum of GD165B was obtained (Kirkpatrick et al. 1993)
•1997: several L dwarfs were discovered (Kirpatrick et al. 1997, Delfosse et al. 1997, Ruiz et al. 1997)
Kirkpatrick et al. 1997Ruiz et al. 1997
Delfosse et al. 1997
Becklin & Zuckerman 1988
Spectral type definition: L dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
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• In 1997 Kirkpatrick proposed a new spectral types and suggest “H”, “L”, “T” or “Y” letters• Martín et al. 1997 was the first to proposed “L” spectral type.
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Kirkpatrick et al. 1998
Martín et al. 1997
Spectral classification of L dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
Kirkpatrick et al. 1999Martín et al. 1999
• Two classification of L dwarfs appear: one base on standards (Kirkpatrick et al. 1999) and other based on pseudo continuum (Martín et al. 1999)
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Early discoveries of T dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
Burgasser et al. 2000
Nakajima et al. 1995
•1995: Nakajima et al. found Gl229B
•1995 fist nIR spectrum of Gl229B was obtained (Oppenheimer et al. 1995)
•1999-2000: several field T dwarfs were discovered by Sloan and 2MASS (Strauss et al. 1999, Cuby et al. 1999, Burgasser et al. 1999, 2000, Leggett et al. 2000)
Oppernheimer et al. 1995
Gl570D
Spectral classification of T dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
Geballe et al. 2002Burgasser et al. 2002
• Two classification of T dwarfs appear: one base on standards (Burgasser et al. 2002) and other based on fluxes ratio (Geballe et al. 2002). Unified scheme in Burgasser et al. 2005
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Discovery of Y dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
Luhman et al. 2011
• Two companions (>T10) found by Luhman et al. 2011 and Liu et al. 2011. Several Y dwarfs discovered by WISE satellite (Cushing et al.2011, Kirkpatrick et al. 2012, Tinney et al. 2012)
Liu et al. 2011
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Cushing et al. 2011
Spectral characteristics of Y dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
Cushing et al. 2011
• Very red optical/near-infrared to mid-infrared colors (Kirkpatrick et al. 2011)• Narrower flux in J, H-band• Possible bluer Y-J and redder J-K color
Kirkpatrick et al. 2012
Are all L and T dwarfs brown dwarfs?
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(Kirkpatrick et al. 2005)
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
A substellarity test: the Li test
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• Substellar objects M<0.060 Msol don’t destroy Li: Li+ p 2 4He
(Chabrier & Baraffe 2000))
The Li test
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• Originally proposed by Rebolo 1991, developed in several papers (Magazzù et al. 1991, 93, Rebolo et al. 1992, Martín et al. 1994, Pavlenko et al. 1995)•Detected in PPL15, Teide1 y Calar3 (Basri et al. 1996, Rebolo et al. 1996).
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Rebolo et al. 1996
Rebolo 1991
The Li test
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• Objects with Li and ages > 120 Myr or Teff<2800K (>M5.5-6) are substellar• Is UX Tau C the first Li brown dwarf?
Basri 2000
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Magazzù et al. 1991, Pavlenko et al. 1995
UX Tau C(M6)
The Li test in T dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• Kirkpatrick et al. 2000 argue that Li disappear at Teff<1500K, but Pavlenko et al. 2000 indicate that line should be present in Teff~1000K
• Li is not detected in Indi B (MBa~74MJup, MBb~47MJup, Cardoso et al. 2010)
• Li in the T0-T0.5 WISE 1049-5319 B (Luhman 16B)? -> YES (see Burgasser’s talk)
King et al. 2010
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Luhman et al. 2013
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Li
Young ultra-cool dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• 1995: Discovery of the M8.5 Teide 1 (Rebolo et al. 1995)• Discovery of first young L dwarfs: Roque25 (Martín et al. 1998), G196-3B (Rebolo et al. 1998)• First ultra-cool M dwarfs in regions <10Myr: Oph (Luhman et al. 1997)• First L dwarfs in regions <10Myr: IPMOs (Lucas & Roche 2000, Zapatero Osorio et al. 2000)• T dwarfs in clusters?: SOri70 (Zapatero Osorio et al 2002), CFBDSIR2149-0403 (Delorme et al. 2012, see his talk), Pleiades (Casewell et al. 2011)
Low gravity and youth features (optical)
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• Strong H emission line in late M dwarfs •Alcaline lines are weaker in low-gravity objects (Martín et al. 1996, but also Steele & Jameson 1995)•TiO and VO are more intense in low-gravity L dwarfs: different classification in opt and IR
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Béjar et al. 1999
Zapatero Osorio et al. 2013(see Zapatero Osorio’s talk)
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Martín et al. 1999
Low gravity features (near-IR)
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• Alcaline lines are also weaker •Triangular shape of H-band• Steeper slope of K-band (see poster by Canty)
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Lucas et al. 2001Mc Govern et al. 2004
Bihain et al. 2010
Low gravity field dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• Kirkpatrick et al. 2006 found a peculiar L dwarf. Several of them presented in Cruz et al. 2009
(Kirkpatrick et al. 2006)
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Zapatero Osorio et al. 2013
L L
Ultra-cool Sub-dwarfs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• First classification of ultra-cool subdwarfs by Gizis 1997: sdM and esdM
• New classification proposed by Lepine et al. 2007: sdM, esdM, usdM
• First low-metallicity L-type objects (Burgasser et al. 2003, Lepine et al. 2003)
• Peculiar blue near-infrared colors and more intense CaH, TiO(see M. Espinoza’s talk)
Burgasser et al. 2003
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Gizis 1997
Isolated UCDs vs. wide companions
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• SED of isolated substellar objects is similar to wide companions
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Chauvin et al. 2004
Chauvin et al. 2005
Exoplanets vs. UCDs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
• SED of isolated substellar objects is similar to exoplanets
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SOri70 & HD189733bZapatero Osorio et al. 2002; Swain et al. 2008
HD189733b (Swain et al. 2008)
Solar System vs. UCDs
Introduction L,T,Y SpT Li test low-g UCD low-metal UCsD exoplanets
Burgasser et al. 2009
• WHAT IS THE SPECTRAL TYPE OF JUPIER?• Is Jupiter a Y-dwarf?
• In the last 25 years, >1000 UCDs have been discovered
• New L, T and Y spectral types have been defined
• Not all of them are brown dwarfs, but some of them are very low mass stars and planetary mass objects
• Gravity (age) and metallicity play a role
• Exoplanets and substellar comunity should work together
Final remarks
