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Reflection Spectra of Giant Planets With an Eye Towards TPF (and EPIC & ECLIPSE)

Reflection Spectra of Giant Planets With an Eye Towards TPF (and EPIC & ECLIPSE) Jonathan J. Fortney Mark S. Marley NASA Ames Research Center 2005 Aspen Winter Conference on Astrophysics: Planet Formation and Detection February 11, 2005. EGP Characterization with an Eye Towards TPF-C.

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Reflection Spectra of Giant Planets With an Eye Towards TPF (and EPIC & ECLIPSE)

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  1. Reflection Spectra of Giant Planets With an Eye Towards TPF (and EPIC & ECLIPSE) Jonathan J. Fortney Mark S. Marley NASA Ames Research Center 2005 Aspen Winter Conference on Astrophysics: Planet Formation and Detection February 11, 2005

  2. EGP Characterization with an Eye Towards TPF-C If TPF-C planetary system targets will be older than 1 Gyr… And if technical limitations will only allow characterization ~1-5 AU from the parent star… This constrains Teff < 400 K and gravity: 1 gSaturn - 10 gJupiter for gas giants Burrows, et al. (2001)

  3. T-P profiles for planets in orbit around the Sun Tint=400K,1 AU Tint=250K,3 AU Tint=100K,5 AU The atmosphere code has been used extensively to model the atmospheres of brown dwarfs and solar system planets Teff < 400 K constrains expected dominant chemical species: Carbon- CH4 Nitrogen- NH3 Oxygen- H2O Expected cloud species: H2O & NH3

  4. Jupiter’s Atmosphere from theGalileo Entry Probe Fairly good agreement with Jupiter’s profile from Galileo Entry Probe Our equilibrium chemistry ignores photochemically produced species that control the heat balance in the Jupiter’s stratosphere.

  5. Jupiter Model BOTTOM: Normalized Flux (at 0.5 µm), Observed vs. Model with solar abunds, no tweaked parameters or hazes. TOP: CH4 absorption coeffs. (Karkoschka,1994)

  6. At long “visible” wavelengths, for the hotter and younger objects, thermal radiation dominates over reflected stellar light Stellar flux is our Sun

  7. What information can be obtained from a few filters? Are clouds and Teff detectable? • TPF-C: 0.5 – 0.8 µm encompasses a very limited spectral region •Signature of clouds is clear (for instance, ratio of X0/X1 filters) •Longer wavelengths, to ~1.04 µm, includes thermal radiation at high Teff •Standard Visible Filters: UBVRI •I-band reaches to 1.04 µm •X2 filter also reaches thermal radiation near Teff ~ 400 K

  8. Color-Color Diagrams BOLD=10X Jupiter g THIN= Jupiter g V,X0,X1 are a diagnostic for clouds. B (~0.45 µm) is better than X0, but perhaps too short in λ X2,V,I are an excellent Teff diagnostic from 400-250K, and fair from 100-250K.

  9. Conclusions EGPs of ages > 1 Gyr, masses below ~ 10 MJ, d > 1 AU are limited in Teff < 400K •All visible spectra dominated by gaseous CH4 absorption •“Clear” (what about hazes?), H2O cloud dominated, and NH3 cloud dominated, are expected (Sudarsky, et al 2000) Discerning clear from cloudy atmospheres can be done from 0.5 – 0.8 µm •This can be done with low-res spectra or a few filters •Determining Teff in this spectral range will be difficult Determining Teff for cloudy planets (Teff< 400K)will be greatlyhelped if TPF-C bandpass is extended to at least to ~1.04 µm • CH4 band depths will help gauge EGP (and perhaps the planetary system’s?) metallicity •I have not yet in detail examined farther into the near IR, but that should be promising, due to the greater thermal radiation

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