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Spectroscopic characteristics of planet-host stars and their planets

Nuno C. Santos (Observatory of Lisbon, Portugal & Geneva Observatory, Switzerland). Spectroscopic characteristics of planet-host stars and their planets. The problem: strange new worlds. Currently ~120 exoplanets are known Difficulty in explaining orbital properties and masses

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Spectroscopic characteristics of planet-host stars and their planets

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  1. Nuno C. Santos (Observatory of Lisbon, Portugal & Geneva Observatory, Switzerland) Spectroscopic characteristics of planet-host stars and their planets

  2. 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

  3. 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)

  4. 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?

  5. 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) Spectroscopic analysis and samples

  6. Average difference 0.25dex Clearly distinctive samples - P(KS)~10-9 Santos et al. 2004

  7. 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)

  8. This is not an artifact of the RV technique Santos et al. (2003) Fischer et al. (2003)

  9. 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?

  10. Using the convective envelope No Correlation! Pinsonneault et al. (2001) Santos et al. (2003)

  11. 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)

  12. 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)

  13. 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!

  14. Two different populations or a flat tail? Santos et al. (2004)

  15. “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)

  16. 6Li in the metal-rich planet-host HD82943(G0V)!Israelian, Santos, Mayor, Rebolo (2001, 2003)

  17. Not original Not produced (flares?) External source is best explanation! Planets and/or planetary material! Not enough to explain excess [Fe/H] How to explain?

  18. 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?

  19. Iron-peek and alpha-elements Bodaghee et al. 2003Sadakane et al. 2002

  20. Iron-peek and alpha-elements Bodaghee et al. 2003Sadakane et al. 2002

  21. C, N, S, ... (Ecuvillon et al. 2004) For other elements: Zn, Cu (Ecuvillon et al. 2004), Na, Mg, Al (Beirao et al. 2004) See poster by Ecuvillon et al. on C, N, O , Zn, and Cu

  22. 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

  23. 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) Light Elements (7Li and 9Be)

  24. Lithium in planet-host stars (Israelian et al. 2004)

  25. Comparison with Chen et al. (2001) samplePlanet-hosts: low Li for Teff between 5600-5850K? (Israelian et al. 2004)

  26. Beryllium in planet-hosts: no clear differenceSantos et al. (2004)

  27. Models with rotational induced mixing(Pinsonneault et al. 1990)Santos et al. (2004)

  28. Internal-wave physics?(Montalban et al. 2000)Santos et al. (2004)

  29. Be. gap for solar temperature stars!Santos et al. (2004)

  30. 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

  31. 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

  32. 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) What about the planets?

  33. Spectroscopy of HD209458b • UV spectroscopy: detection of H, C, and O: exosphere! (Vidal-Majar et al. 2003, 2004) • Planet evaporating!

  34. OGLE candidates! Bouchy et al. (2004) OGLE-TR-113 e 132 • P=1.43 and 1.69 days • M=1.35 and ~1.0 M(Jup)

  35. 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) Prospects...

  36. THE END

  37. Density of planet depends on orbital radius?(see poster by Udry et al.) Bouchy et al. (2004)

  38. 6Li in HD82943: stellar pollution!Israelian, Santos, Mayor, Rebolo (2001, 2003)

  39. Metallicity and Orbital Period

  40. Metallicity and Planetary mass

  41. Metallicity and eccentricity

  42. Stellar mass vs. [Fe/H]

  43. Planets and U,V,W

  44. Planets and U,V,W, [Fe/H]

  45. Be. vs. TeffHow to explain trend?Santos et al. (2004)

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