eduardo martin csic-inta centro de astrobiologia (cab...

Eduardo Martin CSIC-INTA Centro de Astrobiologia (CAB), Madrid

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ULTRACOOL DWARF (UCD=VERY LATE-M, L, T, Y) = VERY LOW-MASS STARS + BROWN DWARF + YOUNG GIANT PLANETS SUBSTELLAR MASS OBJECT = BROWN DWARF + GIANT PLANET

UCDs: Definition! Ultracool dwarfs: Dwarfs with spectral type later than M7 (Teff<2600K). Dust grain condensation in atmospheres (Fe, Al2O3, MgSiO3). !

M. Cushing et al. 2003 ApJ 582, 1066 NIR spectral sequence for UCDs

Brown dwarf: Degenerate e- plasma Limited nuclear fusion

Hayashi & Nakano 1963, Kumar 1963, Chabrier & Baraffe 2000 Martín et al. 1997,1999; Kirkpatrick et al. 1999,2000; Burgasser et al. 2002

Exoplanet search sensitivity critically depends on age

UScoCTIO 108b (V. Béjar et al. 2008 ApJ, 673, L185)

Colour composite image: IJK’ (WHT,TNG) ρ ~ 4.6” (670UA) θ = 177°

Discovery image: J-band 2MASS

Discovery image: I-band IAC80

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

The Upper Scorpius association

•  Distance ~ 145pc •  Age ~ 5 Myr

Spectroscopy of UScoCTIO 108 A & B

UScoCTIO 108 A: •  : M7 •  Low gravity features •  Li is totally preserved •  Signatures of an accretion disks Teff= 2700 ± 100 K

UScoCTIO 108 B: •  : M9.5-L3 •  Low gravity features •  Activity • Teff= 2150 ± 300 K

Physical parameters of UScoCTIO 108 AB

UScoCTIO 108 A: -1.95 ± 0.15 UScoCTIO 108 B: -3.14 ± 0.20

60 ± 20 MJup 14+2-8 Mjup q≈0.2

B. Riaz et al. 2013 A&A, 559, 109 NIR variability & PM

B.P. Bowler et al. 2014 ApJ, in press

2M1207b compared with BDs and PMOs in the Pleiades Deeper H2O bands in low-g UCD spectra Zapatero-Osorio, Martin et al 2014 ApJ Lett. in prep.

HST/WFPC2-PC imaging of 134 late-M and L dwarfs (H. Bouy et al. 2003, AJ, 126, 1526)

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HST/WFC3 imaging of 34 L and T dwarfs (M. Aberasturi et al. 2014, AJ, subm.)

34 L and T dwarfs Within 30 pc 0.13 arcsec/pix (Diffraction limit 0.096—0.14 arcsec) 4 dithers Exp 110s F110W 1200s F164N

Dupuy & Kraus 2013, Science

Binary fraction decreases sharply with diminishing primary mass

No planets detected around T dwarfs yet

J.-Y. Choi et al. 2013, ApJ 768, 129 PLANET follow-up of OGLE events

The sharp drop in binary frequency at the low-mass tail suggests that there is a minimum total mass for binary formation No binaries known yet with Mtot<0.02 Msun (around 20 Mjup) Could this be used as a natural boundary between brown dwarfs and giant planets? More meaningful than D-burning limit??

Paucity of VLM binaries with q=0.4—0.2 Large gap btw q=0.2 and q=10-4

If real this gap could be used to distinguish binaries from planetary systems

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Sample: 20 UCDs (M8—L2) from Phan Bao et al. (2008) I=17.5 – 14.5 J=12.7 – 11.1 VLT/FORS I-band 0.126 arcsec/pix Seeing < 0.9 arcsec Exp 1400 s 11 epochs over 2 years 15 nights

Planet detection limits

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RV of nearby BD much more stable in the NIR than in the optical Martin et al. 2006 ApJ

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High vsini for SpT>M4 a problem for very precise RV

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Red optical spectra of 18 VLM stars observed by the Kepler space telescope (dM4.5—dM8.5)

Kepler light curves of UDs Rotation periods and flare rates measured for most sources

Planet detection limits

Conclusions •  High contrast & spatial resolution imaging surveys of UDs have

revealed the presence of orbiting companions. Sensitivity to planet search highly depends on age for this technique.

•  Spectra of young planetary-mass objects similar to BDs, but accreting exoplanets may be a whole different story

•  Binary frequency sharply drops with decreasing mass of central object. Binary separations get tighter for very low-mass systems.

•  Mass ratio gap between 2M1207b (q=0.2) and MOA-2007-BLG-192Lb (q=10-4)

•  Minimum total mass of known binaries 0.02 Msun (20 Mjup). •  Astrometry and infrared radial velocity are reaching sufficient

precision to detect planets around UDs. Large surveys needed. •  Transits can provide detection of rocky planets around UDs in

habitable region.

Questions •  Mass ratio gap between 2M1207b (q=0.2) and MOA-2007-

BLG-192Lb (q=10-4) Could there be a q gap separating binary BDs from BD-planet systems? •  Minimum total mass of known binaries 0.02 Msun (20 Mjup). Could this be a natural boundary to separate brown dwarfs from giant planets? •  Transits can provide detection of rocky planets around UDs in

habitable region. Could this provide the best chance for characterization of potentially habitable planet using JWST?

Eduardo L. Martín (CAB)

Medium Class mission of the ESA Cosmic Vision 2015-2025

Euclid Independent Legacy Science Team on BDs

David Barrado y Navascués (CAB & CAHA) Hervé Bouy (CAB) Nuria Huélamo (CAB) Nicolás Lodieu (IAC) Basmah Riaz (Univ. Herts., UK) Johannes Sahlmann (Obs. Geneve & CAB) Enrique Solano (CAB & SVO)

Euclid Wide Survey 15,000 sq. deg. (required) VRI 24.5 mag. 10 sigma 0.1 arcsec / pix YJH 24 mag. 5 sigma 0.3 arcsec / pix NIR spectroscopy 1.2—1.8 microns R=250

Euclid Deep Survey 40 sq. deg. (2 regions) VRI 26.5 mag. 10 sigma 0.1 arcsec / pix YJH 26 mag. 5 sigma 0.3 arcsec / pix NIR spectroscopy 0.9—1.8 microns R=250

Spacecraft & Payload Launcher: Soyuz ST-2.1 B from Kourou Launch window: 2020 Orbit: Large Sun-Earth Lagrange point Lifetime: 7 years (required) Maximum science data rate: 850 Gbit/day Telescope: 1.2 m Korsch, f=24.5 m FOV: 0.787x0.709 sq. deg. Detectors: 36 x 4k x 4k CCD, 16 2k x 2k HgCdTe

Ultracool dwarf surface density

Efficient BD identification with VO tools

M. Aberasturi et al. 2011, A&A, 534, L7

Pop II vs III ultracool dwarfs

D. Saumon et al. 1994 ApJ Synthetic spectra indicate it will be possible to tell Pop II from Pop III UCDs using Euclid slitless spectra

Expected SMO Euclid Legacy High precision astrometry, optical/NIR photometry and NIR spectra for about 1 million ultracool dwarfs!

Semimajor axis and mass ratio for about 100,000 resolved ultracool binaries !

Parallaxes, proper motions & variability for about 3,000 ultracool dwarfs !

Discovery of rare ultracool dwarfs, such as Pop II or even Pop III brown dwarfs!

Planets around BD search with imaging, astrometry & photometry !

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