Download Las enanas marrones y planetas aislados: quince años de un

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