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Discovery of a wide planetary mass companion of a very young brown dwarf. “Breaking News” Talk. ApJ Letter La Laguna 2008. Víctor J. S. Béjar. Collaborators: M. R. Zapatero Osorio, A. Pérez-Garrido, C. Álvarez, E. L. Martín, R. Rebolo, I. Villó-Sánchez, A. Díaz-Sánchez. Outline.

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Discovery of a wide planetary mass companion of a very young brown dwarf

Discovery of a wide planetary mass companion of a very young brown dwarf

“Breaking News” Talk. ApJ Letter

La Laguna 2008

Víctor J. S. Béjar

Collaborators:

M. R. Zapatero Osorio, A. Pérez-Garrido, C. Álvarez, E. L. Martín, R. Rebolo, I. Villó-Sánchez, A. Díaz-Sánchez


Outline
Outline brown dwarf

  • Short introduction to substellar objects

  • Discovery of UScoCTIO108B

  • Possible formation mechanisms

  • Relevant results of the letter


Brown dwarfs and planets

(Chabrier & Baraffe 2000) brown dwarf

Brown dwarfs and planets

  • Substellar objects does not stably burn H (M<75 MJup )

  • Brown Dwarfs M<65 MJup does not burn Li (the Li test)

  • Substellar objects M<13 MJupdoes not burn D(Brown dwarf/planet frontier)


Direct image of extrasolar planets
Direct image of extrasolar planets brown dwarf

>250 extrasolar planets discovered

by indirect tecniques

(radial velocity, transits,..)

Secondary transit of an extrasolar planet behind its star with Spitzer (Deming et al. 2005; Charbonneau et al. 2005)

2M1207AB: Enana marrón y planeta en TWA (10 Ma, 70 pc)

(Chauvin et al. 2004, 2005)


Discovery of usco ctio 108b
Discovery of USco CTIO 108B brown dwarf

"Discovery of a wide companion near the deuterium-burning mass limit

in the Upper Scorpius association"

Béjar, V. J. S.; Zapatero Osorio, M. R.; Pérez-Garrido, A.; Álvarez, C.; Martín Guerrero, E. L.; Rebolo, R.; Villó-Pérez, I.; Díaz-Sánchez, A.

2008, ApJ Letter, 673, L185


The upper scorpius association
The Upper Scorpius association brown dwarf

  • Distance ~ 145pc

  • Age ~ 5 Myr


Images of the uscoctio 108 companion
Images of the UScoCTIO 108 companion brown dwarf

2MASS search for red objects (J-Ks>1) around 500 candidates members of USco

Discovery image: J-band 2MASS

Colour composite image: IJK’ (WHT,TNG)

ρ~ 4.6” (670UA)

θ = 177°

Discovery image: I-band IAC80


Photometry of uscoctio 108 a b
Photometry of UScoCTIO 108 A & B brown dwarf

  • Common proper motion with Upper Scorpius association (-11,-25 mas/yr)

  • UScoCTIO108A:µαcosδ,µδ = (-8,-17 mas/yr)

  • UScoCTIO 108B:µαcosδ,µδ= (-6,-20 mas/yr), but large error bar

  • Both objects belong to the photometric sequence of the association


Spectroscopy of uscoctio 108 a b
Spectroscopy of UScoCTIO 108 A & B brown dwarf

  • UScoCTIO 108 B:

  • SpType: M9.5-L3

  • Low gravity features

  • Activity

  • Teff= 2150 ± 300 K

  • UScoCTIO 108 A:

  • SpType: M7

  • Low gravity features

  • Li is totally preserved

  • Signatures of an accretion disks

  • Teff= 2700 ± 100 K


Physical parameters of uscoctio 108 ab
Physical parameters of UScoCTIO 108 AB brown dwarf

Masses from theoretical models

(Burrows et al. 1997; Baraffe et al. 2003)

60 ± 20 MJup

14+2-8 MJup

Mbol=MIJK+BCIJK (SpT)

UScoCTIO 108 A: LogL/Lsol = -1.95 ± 0.15

UScoCTIO 108 B: LogL/Lsol = -3.14 ± 0.20


Binarity of uscoctio 108ab
Binarity of UScoCTIO 108AB brown dwarf

  • Probability ofchance alignment: <<1.3%

  • Projected separation: 670 UA (period 65500 yr)

  • Escape velocity: 0.4Km/s

  • Disruption Time (USco: 0.3 obj/pc3): ≥200 Myr

    (Solar neigh: 0.07obj/pc3): >10Gyr

    <5Myr ->density of birth <20obj/pc3

    (Weinberg et al. 1987; Binney&Tremaine 1987)

  • Dissipation time of Upper Scorpius : ~10Myr

    There could be similar systems at Solar age

  • MJ=15,22 (J=17 a 1pc)

  • Teff=1000, 350 K

  • Sp Type = T6, Y?

Close et al. 2007


Formation of uscoctio 108b
Formation of UScoCTIO 108B brown dwarf

  • DISK

    • Core-Accretion: Similar to the current accepted Solar System models (Pollack et al. 2006).Problem: Only a few Jupiter masses is available at distances <50UA

    • Disk Fragmentation(Boss 2006).Problem: Fragments of 10 MJup con be formed, but at much shorter separations (<100-200UA)

  • Protostellar embryo ejection (Reipurth & Clarke 2001). Problem: Ejection need close encounters which disrupt the system

  • Collapse and Fragmentation of proto-(sub)stellar “cores”:Similar to other stellar binaries are formed(Bodenheimer 1998). Problem:Similar to form isolated planetary mass objects (IPMOs)

    If these systems formed in denser

    environment, they will become IPMOs


Relevant results
Relevant results brown dwarf

  • Direct image and spectroscopy of the least luminous and massive companion, after 2M1206b

  • Substellar companion at the widest projected separation (670UA) and lower gravitational bound energy

  • Key to understand the formation of isolated planetary mass objects

  • Detected in the IAC80!!!


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