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Asteroseismology and exoplanets: a lesson from the Sun *

Asteroseismology and exoplanets: a lesson from the Sun *. Gianni Fiorentini, Barbara Ricci, Andrea Zanzi University and INFN Ferrara. Can we learn on exo-planets from asteroseismology? Metallicity of stars with planets The origin of metals in the Sun photosphere and helioseismology.

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Asteroseismology and exoplanets: a lesson from the Sun *

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  1. Asteroseismology and exoplanets: a lesson from the Sun * Gianni Fiorentini, Barbara Ricci, Andrea Zanzi University and INFN Ferrara • Can we learn on exo-planets from asteroseismology? • Metallicity of stars with planets • The origin of metals in the Sun photosphere and helioseismology. *based on: A. Zanzi, Master Thesis, Ferrara University (2003) and discussions with Castellani Ortolani Paterno’

  2. Laws et al. Astro-ph/0302111 Z=0.024 Z=0.016 Fe/H The Chicken and the Egg dilemma • Stars hosting planets look more metal rich. • The metal content in the convective envelope of a solar type star with Z=0.016 is DMZ=120 Mearth • To reach Z=0.024 an extra 60 Mearth are needed. • Is the excess metallicity primordial or a result of accretion? • Is it a surface/ bulk effect ? Zint < or > Zph • Need a look at the stellar interior: asteroseismology is the natural tool

  3. Dirty solar models The Sun is a natural laboratory Matter is falling onto the Sun (and presumably more was falling in the past) The SSM (without accretion) has been accurately tested with helioseismology (& neutrinos) Build solar models starting wih a lower metacillity and assume metal accretion occurs (shortly) after ZAMS. How much material can have accreted without spoiling the agreement with helioseismology (& neutrinos) ?

  4. NO-DIFF DIFF SSM-SUN The lesson of diffusion • SSM are in excellent agreement with helioseismology (for u, Yph, Rb…) when diffusion is included. • The effect of diffusion is that Zph=0.9 Zint. • This means that helioseismology is sensitive to changing by 10% the metal mass in the convective envelope, i.e. to 12Mearth 1s 3s SUN-MOD

  5. Dirty solar models With respect to SSM, a dirty Sun is metal poor in the interior. molecular weight and opacity are changed Temperature, sound speed, Yph (& Fn) can be changed

  6. 0 10 20 30 DMz [MEarth] Constraints from helioseismology and neutrino SSM • Can study the changement of several observables (sound speed, Yph, Rb, Tc) • Helioseismic observables imply: DMZ <20 MEarth (at 3s) • [Boron neutrino flux gives DMZ <30 MEarth ] SSM

  7. Sun Helioseismology and Asteroseismology • Heliosesimology is sensitive to O(10) Mearth • For asteroseismology we need sensitivity to O(100) Mearth • We are planning simulations ( which frequencies? Which accuracy ? ) • Asterosesismology can prove accretion theory: Zint< Zph • Howevever it cannot disprove it (if accretion occurred before ZAMS) . α Cen A astro-ph/0107099

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