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New Results from Ground-Based Transit Spectroscopy Observations  

New Results from Ground-Based Transit Spectroscopy Observations  . Jacob Bean. Harvard-Smithsonian CfA. University of Chicago. A new technique for ground-based transit spectroscopy. Observation strategy: Time-series spectroscopy with multi-object spectrographs during transits/occultations

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New Results from Ground-Based Transit Spectroscopy Observations  

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  1. New Results from Ground-Based Transit Spectroscopy Observations   Jacob Bean Harvard-Smithsonian CfA University of Chicago

  2. A new technique for ground-based transit spectroscopy • Observation strategy: • Time-series spectroscopy with multi-object spectrographs during transits/occultations • Simultaneous spectra of target and multiple reference stars during transits – “differential spectroscopy” • Wide slits of 12” eliminate slit losses

  3. New Results for GJ1214b: submitted to ApJ and available on astroph • Goals… • Reveal the bulk composition of the planet. • Resolve the tension between conflicting results.

  4. New Results for GJ1214b: submitted to ApJ and available on astroph • New spectroscopy in J, H, and K simultaneously • (Magellan + MMIRS) • New spectroscopy 0.61 – 0.85 μm (VLT + FORS) • New narrow-band photometry at 2.09 μm (VLT + HAWKI) • Re-analysis of previously reported spectroscopy 0.78 – 1.00 μm (VLT + FORS)

  5. NIR Spectroscopy of GJ1214b GJ1214 107 photons per exposure in K-band  50 ppm on the transit depth

  6. NIR Spectroscopy of GJ1214b K-band data

  7. NIR Spectroscopy of GJ1214b Parameter decorrelation

  8. NIR Spectroscopy of GJ1214b

  9. NIR Spectroscopy of GJ1214b 443 ppm per minute 3.4 times the photon noise

  10. NIR Spectroscopy of GJ1214b 652 ppm per minute 6.0 times the photon noise

  11. NIR Spectroscopy of GJ1214b 608 -- 1060 ppm per minute 2.5 times photon noise

  12. Optical Spectroscopy of GJ1214b 504 – 1432 ppm per minute 1.3 times the photon noise

  13. Broadband data for GJ1214b

  14. Broadband data for GJ1214b Our new measurements

  15. Broadband data for GJ1214b Re-analyzed previous measurement

  16. Broadband data for GJ1214b Spitzer data (Desert et al. 2011)

  17. Broadband data for GJ1214b Croll et al. (2011) measurements

  18. Broadband data for GJ1214b • No spectral features detected • Croll et al. (2011) K-band point inconsistent with MMIRS broadband point at 4.1σ

  19. Broadband data for GJ1214b • No spectral features detected • Croll et al. (2011) K-band point inconsistent with MMIRS broadband point at 4.1σ • Solar composition model in chemical equilibrium ruled out at 7.9σ • Solar composition model with methane removed is ruled out at 5.2σ

  20. K-band spectroscopy for GJ1214b • No spectral features detected • Confirm results of Crossfield et al. (2011) at lower resolution

  21. K-band spectroscopy for GJ1214b • No spectral features detected • Confirm results of Crossfield et al. (2011) at lower resolution • Solar composition model in chemical equilibrium ruled out at 4.3σ • Solar composition model with methane removed is consistent

  22. Optical spectroscopy for GJ1214b • No spectral features detected

  23. Optical spectroscopy for GJ1214b • No spectral features detected • Solar composition model in chemical equilibrium ruled out at 6.6σ • Solar composition model with methane removed ruled out at 5.2σ

  24. Summary: • GJ1214… • A remarkably complete ground-based spectrum • Spectrum is flat, no deeper transit in the K-band • Atmosphere is either >70% water, or has high-altitude clouds/haze • Results for other planets with the same technique coming soon

  25. Observation schematic 12” x 30” slits Approx 5’ spectrum

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