Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Spectroscopic characteristics of Spectroscopic characteristics of planet-host stars and their planet-host stars and their

planetsplanets

Nuno C. Santos (Observatory of Lisbon, Portugal & Geneva Observatory, Switzerland)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

The problem: strange new worlds

● Currently ~120 exoplanets are known● Difficulty in explaining orbital properties and

masses● How do giant planets form?

Need to revise theories of planet formation and evolution

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

How to do it?

● Statistical properties of exoplanets (mass, eccentricity, orbital period, ...)

(e.g. Udry et al. 2003; Zucker & Mazeh 2001-2003; Eggenberger et al. 2004)

● Information from the planet-host stars (abundances, rotation, kinematics, ...)

(e.g. Gonzalez 1997-2001, Barnes et al. 2002; Santos et al. 2001-2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Clues from the chemical properties of planet host stars

● Planet host stars are very metal-rich!!!

(e.g. Gonzalez et al. 1997-2003; Santos et al. 2000-2004)

● How to explain this fact?● What is this telling us about the planetary

formation processes?

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Spectroscopic analysis and samples

● Result of uniform comparison of 2 samples:

– 98 planet-hosts (Santos et al. 2004)

– Compared with stars within a limited volume– Same line-lists, atmosphere models, ...

● Similar comparisons done by several authors (e.g. Reid 2002; Laws et al. 2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Average difference 0.25dex

Clearly distinctive samples - P(KS)~10-9

Santos et al. 2004

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Metallicity of planet-hosts

● Difference is clearly significant!● Independ. of method to derive stellar parameters

(e.g. Gonzalez 1997-2001; Gimenez 2000; Santos et al. 2004)

● Not explainable by observational biases:

– No (major) metallicity based samples– No effect due to precision of RV surveys

(Santos et al. 2003; Fischer et al. 2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

This is not an artifact of

the RV technique

Santos et al. (2003) Fischer et al. (2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

The origin of the high-[Fe/H]

● ''Primordial'' origin: to form (these) planets you need metals (e.g. Santos et al. 2001, 2003)

● ''Stellar pollution'': infall of planetary material into stellar conv. envelope (e.g. Gonzalez 1998, Murray 2002)

How can we distinguish?

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Using the convective envelope

No Correlation!

Pinsonneault et al. (2001) Santos et al. (2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Arguments for “Primordial” origin

● No trend in the [Fe/H] vs. Mconv

plot

● Sub-giants with planets also very metal-rich– e.g. HD38529 ([Fe/H]=+0.40); HD27442 ([Fe/H]=+0.39)

● K dwarfs with planets also metal-rich– e.g. HD75732 ([Fe/H]=+0.33); 14 Her ([Fe/H]=+0.43)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Probability of finding planet[Fe/H]=0.0 →~3% ; [Fe/H]=0.3 →~25%

(Santos et al. 2001, 2003, 2004; Reid et al. 2002; Fischer et al. 2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Implications for models:Core accretion vs. disk instability

● Core accretion model: planet formation dependent on dust content (e.g. Pollack et al. 1996; Alibert et al. 2004)

● Disk instability model: not strongly dependent on metallicity (Boss 2002)

Observations are (more) compatible with core accretion model!

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Two different

populations or a flat

tail?

Santos et al. (2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

“Pollution” not generalized but...

● Some evidences for stellar “pollution” events (Gonzalez 1999; Laws 2002; Murray et al. 2002)

● 6Li in HD82943: – Not survive PMS evolution– probably best example (Israelian et al. 2001, 2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

6Li in the metal-rich planet-host HD82943

(G0V)!

Israelian, Santos, Mayor, Rebolo (2001, 2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

How to explain?

● Not original● Not produced (flares?)● External source is best explanation!

– Planets and/or planetary material!● Not enough to explain excess [Fe/H]

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Studies of other elements

● Confirm that the metal excess is global● Look for trends:

– Do planet hosts follow Galactic chemical evolution trends?

– Condensation temperature dependence?

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Iron-peek and alpha-elements

Bodaghee et al. 2003Sadakane et al. 2002

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Iron-peek and alpha-elements

Bodaghee et al. 2003Sadakane et al. 2002

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

C, N, S, ... (Ecuvillon et al. 2004)

See poster by Ecuvillon et al. on C, N, O , Zn, and Cu

For other elements: Zn, Cu (Ecuvillon et al. 2004), Na, Mg, Al (Beirao et al. 2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

General conclusion:

● Similar enrichment for all elements (in the range 0.15-0.30 dex)

● Volatiles (N, C, O, ...) not distinctively different from reflactories

● Abundances follow “normal” Galactic evolution trends

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Light Elements (7Li and 9Be)

● Good tools to look for stellar “pollution”... ● ... and stellar mixing (rotational history?)● Are Li and Be abundances in planet-hosts

different? (Reddy 2000; Gonzalez et al. 2000)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Lithium in planet-host stars

(Israelian et al. 2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Comparison with Chen et al. (2001)

sample

Planet-hosts: low Li for T

eff

between 5600-5850K?

(Israelian et al. 2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Beryllium in planet-hosts: no

clear difference

Santos et al. (2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Models with rotational

induced mixing

(Pinsonneault et al. 1990)

Santos et al. (2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Internal-wave physics?

(Montalban et al. 2000)

Santos et al. (2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Be. gap for solar

temperature stars!

Santos et al. (2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Conclusions

● General metallicity excess in planet-hosts● Primordial origin● Probability of planet-formation strongly

depends on metallicity

– Strong support core-accretion scenario as primary planet formation mechanism

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Open issues...

● What is precisely the P([Fe/H])?● Light elements (Li and Be): some interesting trends

– Lower Li for solar temp. stars with planets? (Israelian et al. 2004)

● How important are pollution events?● Planets and stellar mass? (Santos et al. 2003; Laws et al. 2003)

● Orbital parameters and stellar metallicity? (Gonzalez 1998; Queloz et al. 2000; Santos et al. 2003; Laws et al. 2003)

Poster by Udry, Mayor & Santos

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

What about the planets?

● Currently we cannot resolve the planet● Transiting planets:

– possibility to study the planet itself● First transiting planet around HD209458b:

– Optical spectroscopy - detection of Na (Charbonneau et al. 2000)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Spectroscopy of HD209458b

● UV spectroscopy: detection of H, C, and O: exosphere! (Vidal-Majar et al. 2003, 2004)

● Planet evaporating!

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

OGLE candidates!

OGLE-TR-113 e 132

● P=1.43 and 1.69 days

● M=1.35 and ~1.0 M(Jup)

Bouchy et al. (2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Prospects...

● More and more transits are needed...● Around “bright stars”● Space missions like COROT, etc...● Spectroscopy of hot-jupiters with the VLTi

(Segransan et al. 2000)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

THE END

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Density of planet depends

on orbital radius?

(see poster by Udry et al.)

Bouchy et al. (2004)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

6Li in HD82943:

stellar pollution!

Israelian, Santos, Mayor, Rebolo (2001, 2003)

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Metallicity and Orbital

Period

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Metallicity and

Planetary mass

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Metallicity and

eccentricity

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Stellar mass vs. [Fe/H]

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Planets and U,V,W

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Planets and

U,V,W, [Fe/H]

Nuno C. Santos Cool Stars 13 - Hamburg, Germany - July2004

Be. vs. Teff

How to explain trend?

Santos et al. (2004)