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IX Reunión Científica de la Sociedad Española de Astronomía. Madrid, 17 Septiembre 2010 Las enanas marrones y planetas aislados: quince años de un descubrimiento Víctor J. S. Béjar (IAC) Teide 1 : Discovery of the first brown dwarf (1995) First brown dwarf: Teide1 Discovered in the Pleiades cluster (Rebolo, Zapatero Osorio & Martín et al. 1995, Nature, 377, 129) 14 Septiembre 1995 Brown Dwarfs exist - official ¡ FELIZ ANIVERSARIO! Outline • Definition and introduction to substellar objects • First discoveries • Recent relevant results • Future of the substellar field • Summary Introduction First discoveries Recent Results Future Perspectives Summary Brown dwarf and planet concept • Brown dwarf: Object unable to fuse hydrogen stably in its interior (Mass < 0.072 Msol ~ 75 MJup) • Planet (Old concept): Object orbiting a star and visible from the reflected light • Planet (New concept): – Object unable to burn deuterium in its interior (M < 0.012 Msol ~ 13MJup) – Object orbiting a star and formed in a protoplanetary disk – IAU working definition: Object orbiting a star and unable to burn deuterium Introduction First discoveries Recent Results Future Perspectives Summary IAU working definition Emphasizing again that this is only a working definition, subject to change as we learn more about the census of low-mass companions, the WGESP has agreed to the following statements: 1) Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets" (no matter how they formed). The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System. 2) Substellar objects with true masses above the limiting mass for thermonuclear fusion of deuterium are "brown dwarfs", no matter how they formed nor where they are located. 3) Free-floating objects in young star clusters with masses below the limiting mass for thermonuclear fusion of deuterium are not "planets", but are "sub-brown dwarfs" (or whatever name is most appropriate).These statements are a compromise between definitions based purely on the deuterium-burning mass or on the formation mechanism, and as such do not fully satisfy anyone on the WGESP. However, the WGESP agrees that these statements constitute the basis for a reasonable working definition of a "planet" at this time. We can expect this definition to evolve as our knowledge improves. Introduction First discoveries Recent Results Future Perspectives Summary Substellar objects physical properties • Interior of nearly totally ionized H+He plasma and partially degenerated electron gas. • Totally convective interior (Politropo with n=1.5) • log L/Lsol < -1.5 • Teff < 3000 K (Spectral types: late M, L, T...) • Cold Atmospheres (condensation: Ti, V, Fe …) • Physical properties change with time Introduction First discoveries Recent Results Future Perspectives Substellar objects radius Substellar radius is ~ 1 RJup R ~ cte Degenerated plasma R ~ M-1/3 and Coulomb pressure Degenerated plasma R~M Summary Introduction First discoveries Recent Results Future Perspectives Summary Spectral classification and effective temperature L class: Teff = 2200-1500K Dust grain condensation (TiO,VO -> perovskite, enstatite,..), Stronger Alcaline Lines (Li, Na, K, Rb, Cs) and hidrures (FeH, CrH) T class: Teff = 1500-600K Dust deposits below the photosphere Alcalines and hidrures disappear Stronger H2O bands Appearance of CH4 bands Introduction First discoveries Recent Results Future Perspectives Substellar formation models • Turbulent fragmentation: Extension of the stellar formation toward lower masses (Padoan & Nordlund 2002, 2004) • Fragmentation, photo-ionization or ejection of proto-stellar “cores” (Bodenheimer 1998, Whitworth & Zinecker 2004, Reipurth & Clarke 2001 ) STAR FORMATION • Disk fragmentation (Boss et al. 1997) that can be later ejected (Jiang et al. 2004; Stamatellos & Whithworth 2009 ) • Core-Accretion (Pollack et al. 1996) PLANET FORMATION Summary Introduction First discoveries Recent Results Future Perspectives Summary Teide 1 y Gl229B: First brown dwarfs First brown dwarf: Teide1 in the Pleiades cluster (Rebolo et al. 1995, Nature, 377, 129) 14 Septiembre 1995 Second brown dwarf: Gl229B T companion of a star in the Solar vecinity (Nakajima et al. 1995, Nature, 378, 463) 30 Noviembre 1995 Introduction First discoveries Recent Results Future Perspectives First L dwarfs • GD165B: White dwarf companions (Becklin & Zuckerman • • • • Kelu1: First field L brown dwarf (Ruiz et al. 1997). DENIS survey: (Delfosse et al. 1997) 2MASS survey: (Kirkpatrick et al. 1997, 1999, 2000) Roque 25: First L brown dwarf in a young cluster • Gl196-3B: First young L brown dwarf companion • IPMOs: First Isolated Planetary-Mass Objects • 2M1207b: First direct image of a planetary-mass companion (Chauvin et al. 2004) LSR1610-0040, 2M0532+82: First low-metallicity L objects (Lepine et al. 2003; Burgasser et al. 2003) • 1988) (Martín et al. 1998) (Rebolo et al. 1998) (Lucas & Roche 2000; Zapatero Osorio et al. 2000) Spectral classification of L dwarfs (Kirkpatrick et al. 1999; Martín et al. 1999) Summary Introduction First discoveries Recent Results Future Perspectives Summary First T dwarfs • • • • Gl229B: (Nakajima et al. 1995) 2MASS survey: (Burgasser et al. 1999, 2000) Sloan survey: (Strauss et al. 1999; Fan et al. 2000) SOri 70: First T in a young cluster (Zapatero Gl 570D Osorio et al. 2002) Spectral classification of Ts (Burgasser et al. 2002; Geballe et al. 2002) • Coolest brown dwarfs (Teff=500-600K,Y class?): Burningham et al. 2008, 2009; Delorme et Burgasser et al. 2000 al. 2008 Zapatero Osorio et al. 2002 Burningham et al. 2009 Introduction First discoveries Recent Results Future Perspectives Summary The Substellar Mass Fuction • First substellar mass functions in cluster: – Pleiades (Bouvier et al. 1998), but also in Zapatero Osorio et al. 1997 – IC348 (Luhman et al. 1999) – Orion Nebula, ρ Ophiucus (Luhman et al. 2000) – σ Orionis (Béjar et al. 2001) • First substellar mass function in the field: (Reid et al. 1999; Chabrier et al. 2001; Kroupa et al. 2001) Brown dwarfs are very numerous, but are <10% mass Bouvier et al. 1998 Kroupa 2002 log m (Msol) Introduction First discoveries Recent Results Future Perspectives Summary Physical properties of brown dwarfs • • • • First measurement of parallaxes, luminosity and bolometric corrections of L and T dwarfs (Dahn et al. 2002; Vrba et al. 2004; Golimowski et al. 2004) GJ569Bab: First measurement of dynamical masses of a binary brown dwarfs: 70 and 55 MJup(Zapatero Osorio et al. 2004) First eclipsing binary brown dwarf in the Orion Nebula (Stassun et al. 2006). Measurement of the Teff, radius and masses of young brown dwarfs CoRoT-exo-3b: Measurement of the radius of an evolved brown dwarf (Deleuil et al. 2008) Zapatero Osorio et al. 2004 Stassun et al. 2006 Deleuil et al. 2008 Introduction First discoveries Recent Results Future Perspectives Summary Dynamical masses of brown dwarfs • The star/brown dwarf borderline is ~M6-L/T depending on the age • Models subestimate the Luminosity of substellar objects or most of these bd binaries are young • Precise determination of age is necessary in these systems: asterosismology HD130948? Name MTot Sp. Type GJ569Bab 0.125 M8+M8.5 2M0746+20 0.146 L0+L1.5 AB DorC 0.090 M5.5 2M0535-05AB 0.088 M6.5+M6.5 2M1534-29AB 0.056 T5.0+T5.5 GJ802B 0.063 mid-L HD130948 BC 0.109 L4+L4 LHS2397AB 0.146 M8+L7 2M2206-20 0.150 M8+M8 Eps. IndiBab 0.120 T1+T6 Bouy et al. 2004 Liu et al. 2008; Dupuy et al. 2009a,b,c Close et al. 2005 Femenía et al. 2010 Bouchy et al. 2010 Introduction First discoveries Recent Results Future Perspectives Summary Disks in brown dwarfs and isolated planets • First evidence of discs and accretion • Planetesimal formation in disks around brown dwarfs? (Apai et al. 2005) Disk fraction is similar in substellar objects than in low-mass stars • (Jayawardhana et al. 2002; Muzzerolle et al. 2003; Natta & Testi 2001) -Taurus:40-80/61% (Hartman et al. 2005, Luhman et al. 2006; Guieu et al. 2007) - IC348: 42/33% (Luhman et al. 2005) - Chamaleon I: 50-58/45-65% (Luhman et al. 2005, 2008; Damjanov et al. 2007) - Chamaleon II: 80/80% (Alcala et al. 2008) - Sigma Orionis: 50/47/33% (Caballero et Pascucci et al. 2003 al. 2007; Zapatero Osorio et al. 2007; Hernández et al. 2007; Scholz & Jayawardhana 2008; Luhman et al. 2008) - Lambda Ori: 40%/25% (Barrado y Navascués et al. 2007) - Upper Scorpius: 11-50%/>35% (Bouy et al. 2007; Scholz et al. 2007; Riaz et al. 2009) - TW Hya: 60 /24% (Riaz et al. 2008) Apai et al. 2005 Introduction First discoveries Recent Results Future Perspectives Summary Isolated Planetary-mass objects: the lowmass end of the mass function? Current Isolated Planetary-mass objects: -Sigma Orionis: 22 L candidates (11 with spectra, 6 confirmed members 2 T candidates (1 with spectrum) (Zapatero Osorio et al. 2000, 2002a,b; Barrado y Navascués et al. 2001; Martín et al. 2001; Caballero et al. 2007; Bihain et al. 2009) -Trapezium: 15 L candidates (10 with spectra, 6 confirmed members (Lucas&Roche 2000; Lucas et al. 2001, 2006; Weights et al. 2008) -Upper Scorpius: 9 L candidates with spectra (Lodieu et al. 2007, 2008) -Chamaleon I: 2 L confirmed members (Luhman et al. 2008a,b) -Taurus: 1 L confirmed member (Luhman et al. 2009) -IC348: 1 T candidate (Burgess et al. 2009) Bihain et al. 2009 The mass spectrum is rising down to ~6MJup A decrease below these masses? Introduction First discoveries Recent Results Future Perspectives Summary Direct image of planetary-mass companions 2M1207 AB Pic CHRX 73 UScoCTIO 108 260 AU 200AU (Béjar et al. 2008) (Chauvin et al. 2004) (Chauvin et al. 2005) (Luhman et al. 2006) Formalhaut DH Tau 330 AU 1RXS J1609-21 HR8799 (Lafeniere et al. 2008) Beta Pic (Itoh et al. 2005) (Kalas et al. 2008) (Marois et al. 2008) (Janson et al. 2010) • Wide separations (8-700UA) and masses (>4MJup) • Low frequency (~1-2%) (Lagrange et al. 2009, 2010) Introduction First discoveries Recent Results Future Perspectives Summary Mid-IR searches for substellar objects Mid-IR searches (CanariCam@GTC, MIRI@JWST) are more sensitive for less massive and older substellar objects. Introduction First discoveries Recent Results Future Perspectives Summary Mid-IR searches for substellar objects CanariCam MIRI/JWST@ 50pc CanariCam could detect some of the coolest substellar objects (Teff bellow ~500K) in the Solar vecinity MIRI will detect these objects up to distances of 100pc MIRI Introduction First discoveries Recent Results Future Perspectives Summary Searh for earth-like planets around brown dwarfs [email protected]: Near-IR and optical high-resolution spectrograph With a radial velocity precission of 1m/s, we can detect 1m⊕ around objects with masses <0.07MSol (Sp. types >L2.5) NIRINTS@GTC: Near-IR mid and high-resolution spectrograph Introduction First discoveries Recent Results Future Perspectives Summary Summary • Since the discovery of first brown dwarfs: Teide 1 and Gl229B, in 1995, hundred of brown dwarfs and decens of planetary-mass objects have been found. • All these investigations have led to the conclussion that brown dwarfs are as numerous as low-mass stars and isolated planetary-mass objects up to 6 Mjup are about 30% of brown dwarfs • Recently, we have been able to directly measure the luminosity, radius and dynamical masses of brown dwarfs, entering in a new domain of “SUBSTELLAR ASTROPHYSICS” • Next future, we expect to detect the coolest substellar objects in the Solar neighborhood. Maybe the first earth-like planet will be detected around a brown dwarf