A young massive planet in a star-disk system Setiawan, Henning, Launhardt et al. January 2008, Nature Letter 451 ESO Journal Club – January 2008

The target: TW Hya Spec. Type K7 V Distance (pc) 56 ± 7 Mass (M סּ ) 0.7 ± 0.1 Radius (R סּ ) 0.9 ± 0.1 Teff (K) 4000 ± 150 L (L סּ ) 0.20 ± 0.05 Age (Myr) 8-10 v.sin i (km/s) 5 - 7

The disk around TW Hya Krist et al HST/ WFPC R and I-band Trilling et al HST / H-band corono. TW Hya is surrounded by a Nearly face-on disk

The disk around TW Hya Qi et al. 2004, sub-mm +- 1 TW Hya is an almost pole-on system

The accretion disk around TW Hya In CCTS: Strong accretion declines with age At 10 Myr: no more accretion (disk lifetime) In TW Hya: Optical spectrum shows strong emission lines related with accretion processes Accretion rate ~ 1e-9 Msun/yr At 10 Myr, the object is still accreting !!

Planets around TW Hya? Calvet et al SED modeling: Inner Disk clearing as a consequence of planet formation Lack of IR excess below 10 Microns Gap in the inner disk ( AU)

Planets around TW Hya? Setiawan et al. 2008: Hunting planets using RV techniques Advantage: they can study planets in closer orbits Disadvantages: TW Hya is a young and very active star (radial velocity variations due to spots, pulsations…) Moreover, it is an accreting star ??? High contrast imaging techniques have not revealed the presence of a planet at separations > 5 AU (e.g., Apai et al. 2004).

Planets around young, active stars: the RV technique Setiawan et al. 2007

Planets around young, active stars: the RV technique TW Hya (8-10 Myr) Setiawan et al. 2007

TW Hya: RV observations FEROS observations 2.2 m MPG/ESO telescope 2 data sets from two observing runs: 12 consecutive nights between 28th FEB – 12th MAR consecutive nights between 24th APR – 13th MAY 2007 First run : 33 data points Second run : 33 data points Setiawan et al. 2008, Nature Letter

TW Hya: RV results I. RV Variations Setiawan et al. 2008, Nature Letter RV amplitude: 198 ± 60 m/s RV accuracy: 40 m/s

TW Hya: RV results II. Periodic RV variations Setiawan et al. 2008, Nature Letter FAP (3.56 days)= 1e-14 Three possible periods Scargle periodogram

TW Hya: RV results Setiawan et al. 2008, Nature Letter

RV variations: Activity or a planet? Queloz et al. 2001, Line Bisector Analysis: Cross-correlation function Velocity span= Vt – Vb _ CCF star Bisector of the CCF

RV variations: Activity or a planet? Setiawan et al. 2008, Nature Letter TW Hya Bisector analysis of the CCF: No correlation with the RV Variations The RV variations are not related with stellar activity. then… COMPANION

The planet around TW Hya Setiawan et al. 2008, Nature Letter

The planet around TW Hya Setiawan et al. 2008, Nature Letter Plotoplanetary disk are really protoplanetary…

The planet around TW Hya: Implications for planet formation theories? Setiawan et al. 2008, Nature Letter Core accretion vs Disk Instability Planet formation and migration must be completed within 10 Myr Santos et al Timescales of planet formation? Metallicity? Core accretion predicts more efficient planet formation around metal-rich stars [M/H] = ± 0.12 (Yang et al. 2005) Mass? Core accretion predicts a deficit of massive planets (Mp > 3 Mjup) at small separations (a < 0.2 AU) 9.8 Mjup at 0.04 AU

Accretion processes in CTTS - Hot spots on the stellar surface (filling factor = 0.1 – 5%) - Accretion shocks: Excess Continuum Emission (veiling) - Emission lines in the accretion columns - Disk winds

Accretion & RV observations Accretion – RV variation? Correlation between bisector and RV? Can veiling affect the RV measurements? Timescale of accretion processes?

TW Hya: Photometric Variability What is the origin of the brightness modulation? Lawson & Crause 2005 Hot spots on the surface 2 weeks of monitoring

TW Hya: Photometric Variability Batalha et al B-band observations

TW Hya: Accretion signatures Batalha et al Alencar & Batalha 2002 lines veiling lines Line emission and Continuum variability not in phase

TW Hya: Timescale of Accretion Events ( Bouvier et al.2004) ‘The accretion is a highly time dependent process on timescales ranging from hours to months, maybe even years…’ The fact that Setiawan et al. are able to reproduce the same periodicity in 2 independent datasets strengthens the planet interpretation In the case of TW Hya … The orbital period is ‘close’ to the ones found in TW Hya Accretion events. TW Hya: Up to know variable periodicities (due to accretion) within years, not months… And the target is one of the oldest CTTS (accretion rate ~2 orders of magnitude smaller than younger CTTS)

TW Hya: RV & Accretion What is important in the case of RV studies? Accretion shocks 1. Hot continuum excess (veiling) - It varies the depth of the absorption lines, it can affect the RV calculation and produce variable CCF - It does not affect the line profile 2. Hot spots: stellar surface inhomogeneity - What is the expected RV variation? Size, Temperature - Do they change the line profile? - Is the bisector correlated with the RV variation?

RV & Veiling Veiling: change in continuum level and, therefore, in the absorption depth of spectral lines It is wavelength dependent Alencar & Batalha 2002 Batalha et al TW Hya Photosphere

RV & Veiling And the bisector? Veiling: Variable CCF Hot spots: RV correlated with the bisector?

RU Lup: Activity, accretion or a companion? Stempels et al RU Lup CTTS K7 Teff = 4000 K Dist ~ 200 pc Age ~ 2-5 Myr Ṁ = 10e-7 M סּ /yr v.sin i = 9 km/s Inclination ~ 24 deg Activity and accretion RV variations RV amplitude = 2.2 Km/s Period = 3.7 days Error = 0.2 Km/s Activity, accretion, companion?

RU Lup: Activity, Accretion or planet? Stempels et al The RV variations are related with stellar activity.

RV: Activity, Accretion or planet? Stempels et al RV variation vs the spot properties (Size,temperature) Hot spots: They cover 0.1 – 5 % of the stellar surface of CTTS They need a 40 deg hot spot with 7000 K to get 2.2 Km/s Cold Spot Model

RU Lup: Activity, Accretion or planet? Stempels et al The RV variations can be modelled with a big dark spot To create such spots, they estimate B ~ 3 kG) Model R spot = 35 deg T spot = 3400 K

RU Lup vs TW Hya Stempels et al RV variation vs the spot properties (Size,temperature) 5 degrees Hot spots: They cover 0.1 – 5 % of the stellar surface of CTTS TW Hya: f~ %, Tspot ~8000K B = 2.61 ± 0.23 kG --- Cold spots must be present.…

Some final remarks… If the planet is real: The detection of the planet confirms that protoplanetary disks are certainly protoplanetary… Comparison with planet formation theories will provide new clues about the planetary formation process The theories should try to reproduce the formation of this planet My personal conclusions: (I think) Some work on RV and Accretion is needed for these stars