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The Polarization Signature of Extrasolar Planets Transiting Cool Dwarfs

The Polarization Signature of Extrasolar Planets Transiting Cool Dwarfs. Antonio Mário Magalhães Alex C. Carciofi IAG Universidade de São Paulo, Brazil. Collaborators :. Polarimetry Group at IAG-USP : Alex Carciofi (Pos–doc) Antonio Pereyra (Pos-doc) Rodolfo Valentim (MSc student)

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The Polarization Signature of Extrasolar Planets Transiting Cool Dwarfs

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  1. The Polarization Signature of Extrasolar Planets Transiting Cool Dwarfs Antonio Mário Magalhães Alex C. Carciofi IAG Universidade de São Paulo, Brazil 2nd CoRoT Meeting

  2. Collaborators: • Polarimetry Group at IAG-USP: Alex Carciofi (Pos–doc) Antonio Pereyra (Pos-doc) Rodolfo Valentim (MSc student) Flaviane Benedito, Viviana Gabriel, Fábio Godoy, Cássio Alves, Reinaldo Caraça, Suryendrani Batista (Undergrads) Cláudia Rodrigues (INPE/DAS) • Acknowledgements • FAPESP - São Paulo State Funding Agency • CNPq, CAPES - Federal agencies 2nd CoRoT Meeting

  3. Summary • Motivation • Analytical Results • Approximation formulae • Numerical Results: • Monte Carlo code • G dwarfs • K, M & T dwarfs • Conclusions & Perspectives 2nd CoRoT Meeting

  4. Venus transit, 2004 June Motivation Magalhães 2nd CoRoT Meeting

  5. Venus transit, 2004 June Break in spherical symmetry! Motivation Magalhães 2nd CoRoT Meeting

  6. Visible Sun (mostly) spherical Motivation 2nd CoRoT Meeting

  7. Visible Sun (mostly) spherical P  10–5 % in V band Kemp 1987 Motivation 2nd CoRoT Meeting

  8. Visible Sun (mostly) spherical P  10–5 % in V band Kemp 1987 Sun has Limb Polarization centro–symmetric increases towards the limb Motivation 2nd CoRoT Meeting

  9. Visible Sun (mostly) spherical P  10–5 % in V band Kemp 1987 Sun has Limb Polarization centro–symmetric increases towards the limb @ 6000A Motivation Leroy 72 2nd CoRoT Meeting

  10. Visible Sun (mostly) spherical P  10–5 % in V band Kemp 1987 Sun has Limb Polarization centro–symmetric increases towards the limb Motivation Leroy 00 2nd CoRoT Meeting

  11. An occultation will break the spherical symmetry  polarization signal! Potential probe to stellar atmosphere orbital parameters Observable? Motivation 2nd CoRoT Meeting

  12. Flux from star: Net flux: Stokes Parameters: P()= limb polarization f() = limb darkening Analytical Results Carciofi & Magalhães 05, ApJ Dec 2nd CoRoT Meeting

  13. Analytical approximations The maximum Occultation Polarization (OP) is: where The maximum OP depends on: larger  larger OP Analytical Results 2nd CoRoT Meeting

  14. Analytical approximations The maximum Occultation Polarization (OP) is: where The maximum OP depends on: larger  larger OP larger Rp, smaller  smaller OP Analytical Results 2nd CoRoT Meeting

  15. Monte Carlo simulations Limb Darkening Sun: Claret 00 Limb Polarization Sun: Fluri & Stenflo 99 for other Sp Types: explore Pl = value at limb Numerical Results Carciofi & Magalhães 05 Red Giant k=0 1 5 50 Sun 2nd CoRoT Meeting

  16. Monte Carlo simulations Limb Darkening Limb Polarization: Planet radii: 0.09 – 2 RJup a = 0.04 UA (Silva & Cruz 05) Transit geometries for 1 Rjup & 2 Rjup in front of Sun .5 Rjup & 1 Rjup in front of M2V .2 Rjup & .4 Rjup in front of TV Numerical Results 2nd CoRoT Meeting

  17. Results for Sun–like star Flux: Limit of detectability Hough & Lucas 03 (@ 4600A) Polarization: Numerical Results Carciofi & Magalhães 05 1 RJup 2 RJup 2 RJup 1 RJup 2nd CoRoT Meeting

  18. Results for Sun–like star Flux: (@ 4600A) Polarization: Numerical Results 1 RJup 2 RJup 2 RJup 1 RJup 2nd CoRoT Meeting

  19. Results for Sun–like star Flux: CaI 4226A (Pl from Bianda et al. 99) Polarization:  Much higher P than @ continuum! Numerical Results Carciofi & Magalhães 05 1 RJup 2 RJup 2 RJup 2 RJup 1 RJup 1 RJup 2nd CoRoT Meeting

  20. Results for M5 dwarf + 1 RJup We define  = ‘efficiency’ of star–planet system For detection of polarization: Ex: if Pl~1%  > 10–4 for detectability of P Central occultation, @4600A Numerical Results k=0 1 5 50 Carciofi & Magalhães 05 2nd CoRoT Meeting

  21. Results for M5 dwarf + 1 RJup We define  = efficiency of star–planet system For detection of polarization: Ex: if Pl~1%   > 10–4 for detectability of P @4600A Numerical Results Carciofi & Magalhães 05 2nd CoRoT Meeting

  22. Results for a T dwarf + 1 RJup Numerical Results Carciofi & Magalhães 05 k=0 k=0 1 1 5 5 50 50 2nd CoRoT Meeting

  23. Summary of expected Occultation Polarization  Non–symmetrical OP curves  eccentricity! (eg., from CoRoT sample) P=10–6 can be obtained in 1h for V=9 & 4m telescope CoRoT will likely detect longer transits as well, and higher P values expected Note: Detectability: 10–6 = 10–4 % Hough & Lucas 03 Numerical Results Carciofi & Magalhães 05 2nd CoRoT Meeting

  24. For G dwarfs OP is generally large enough for 1 RJup resonant lines favored For K–, M–, T–dwarfs: least favourable cases: 1 RJup, 1 RNep possible more favourable cases: 1 REarth possible for M, T types OP)max during occultation independent of incl. angle Obtaining orbital eccentricity possible Summary of Occultation Polarization (OP) 2nd CoRoT Meeting

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