Exploring the giant planet - brown dwarf connection with astrometry. Johannes Sahlmann ESA Research Fellow at ESAC

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1 Exploring the giant planet - brown dwarf connection with astrometry ESA Research Fellow at ESAC Who s Who, Paris - 2 July 215

2 IS MASS A GOOD DEMOGRAPHIC INDICATOR? 2MASSWJ first image of a planetary mass companion in a different system than our own (Chauvin et al., A&A, 25) M 1 ~ 25 M Jup M 2 ~ 5 M Jup mass ratio q mas 55 AU at 7 pc N E Planet masses and radii are difficult to measure (in nontransiting systems) N Astrometry gives a good handle on companion masses E 2

3 HIGH-MASS TAIL OF PLANET MASSES OVERLAPS WITH SUBSTELLAR COMPANIONS IN BINARY SYSTEMS J. Sahlm 15 J. Sahlmann et al.: Search for brown-dwarf companions of stars HD radial velocity survey of 1647 GK dwarfs: 4 5 RV [m/s] RV [m/s] 1 discarded as M-dwarfs by Hipparcos N φ.. 5 astrometry (Sahlmann et al., 211, A&A, 525) M2 =.52 ±.5 M. M2 sin i = 49 ± 2 MJup 15 2 companions with M2 sin i = 13-8 MJup.1. HD17289 Δδ (mas). HD φ HD MIKE. HD E a).6 ±.2 % of Sun-like stars have a brown dwarf HD b) no indication for discontinuity at 13 MJup 1 8 φ Cumulative distribution companion within 1 AU.1. c) mass distribution indicates minimum occurrence RV [m/s] RV [m/s] 2 at ~25-45 MJup (see also Grether & Lineweaver 26) HD φ Giant Planets 2 Void Orbital phase HD Brown dwarf companions HD8977 φ.. HD φ Δδ (mas) M2 sin i (MJ) V [m/s] V [m/s] O C (mas) RV [m/s] RV [m/s] 1 Δα* (mas)

4 WHAT IS THE PLANET MASS DISTRIBUTION AROUND ULTRACOOL DWARFS? Astrometric survey with FORS2 camera at VLT (Sahlmann et al. 214, Lazorenko et al. 214) Monitoring 2 nearby late-m and early-l dwarfs since 21 Long-term astrometic precision ~.1 milli-arcsec (Lazorenko et al. 29 & 211) sensitive down to Neptune-mass planets in ~1 day orbits 8 DE (12) 6 δ (mas) α* (mas) DE (13) DE (14) 4 4

5 GIANT PLANETS ARE RARE AROUND ULTRACOOL DWARFS (AT ALL SEPARATIONS) Companion mass (M Jup ) Separation (AU) companions excluded by data Period (days) Less than 9 % of M8-L2 dwarfs have a giant planet >5MJup within.1-.8 AU (Sahlmann et al. 214) Ongoing follow-up of planet candidates 5

6 DETECTION OF THE ORBIT CAUSED BY A LOW- MASS COMPANION L1.5 dwarf P = ±.6 days e =.36 ±.4 α = 4.62 ±.12 mas Parallax = ±.14 mas 16 epochs residual RMS 17 µas Derived properties depend on age estimate Sahlmann et al., 213, A&A 556 6

7 A JUVENILE BINARY BROWN DWARF AT 2.7 PC Li I absorption detected in optical spectrum age constraint spectral binary in the near-infrared spectral types L1.5 + L5.5 Teff = 215 ± 1 K and 167 ± 14 K Normalized F λ DENIS J DENIS-P J L1.8 2MASS J L6.3:: χ 2 = Wavelength (µm) Combined astrometric and spectroscopic constraints + evolutionary models: Age = 8-5 Myr M M M M mass ratio q Sahlmann, Burgasser, et al. 215, A&A Wavelength (µm) Fig. 6. Results of spectrum fitting with binary templates (cf. Fig. 5). Top: When using all templates, the SpeX spectrum of DE (black line) is best fit by the binary template (brown line) that is a 7

8 A GIANT PLANET AROUND LUH16? WISE J (Luhman 213) 2 pc distance ~3 AU binary: L7.5 + T.5 (Burgasser et al. 213, Faherty et al. 214) Possible detection of a giant planet in a short-period orbit around one component (Boffin et al. 214) We analysed 22 epochs of public FORS2 data (PI: Boffin) taken over 1 year Applied Lazorenko s techniques to obtain astrometry of both components Individual fits are poor, data of both components have to be modelled jointly 8

9 BARYCENTRE FIT IS GOOD AND DETERMINES THE MASS RATIO ΔxB mass ratio q = MB / MA = ΔxA / ΔxB Reconstructed barycentre motion as a function of mass ratio: ΔxA? = = 1 1+q (? A + q B)? 1 ( 1+q A + q B ). q =.78 ±.1 ompanion aroun direct measurement (no models), independent of distance and orbit r.m.s. =.23 mas Sahlmann & Lazorenko, submitted, arxiv:

10 NO GIANT PLANET AROUND LUH16, YET companions excluded by data M A.6 M / M B.47 M (3 Gyr) M A.3 M / M B.23 M (.5 Gyr) Sahlmann & Lazorenko, submitted, arxiv:

11 GAIA S EXOPLANET AND BD YIELD 5-year all-sky survey, G < 2 mag Gaia will deliver high-precision astrometry of 1 million stars (+ photometry, spectroscopy) ESA Nominal mission began July 214 Gaia will discover thousands of giant extrasolar planets with masses higher than Saturn and periods shorter than ~2 days. (Casertano et al. 28, Sozzetti et al., 214, Perryman at al., 214, Sahlmann, Triaud & Martin 215) For Sun-like stars, Gaia astrometry will detect 3 MJup companions out to distances of ~.8 kpc and 6 MJup out to ~1.7 kpc Gaia will uniformly yield the masses and orbital parameters of hundreds of companions in the brown-dwarf mass range. 11

12 CONCLUSIONS Mass alone is not a good demographic indicator: A 35 MJup companion to a Sun-like star may have formed like a planet or like a binary. Astrometric surveys of ultracool dwarfs are sensitive to giant planets and reveal binaries with planetary-mass components. Super-Jupiters are rare at all separations. The mass ratio of the 2-pc binary brown dwarf LUH16 is.78 +/-.1. There is no indication for a giant planet in a short-period orbit around either component. Gaia s survey will provide a comprehensive census of substellar companions more massive than Saturn in the solar neighbourhood. Thanks to: P. Lazorenko (Kiev), E. Martín (Madrid) D. Ségransan, M. Mayor, D. Queloz, S. Udry & Geneva planet group A. Burgasser & D. Bardalez-Gagliuffi (San Diego) 12