new results from ground-based transit spectroscopy observations
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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New Results from Ground-Based Transit Spectroscopy Observations
Jacob Bean
Harvard-Smithsonian CfA
University of Chicago
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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
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Goals…
•Reveal the bulk composition of the planet.
•Resolve the tension between conflicting results.
submitted to ApJ and available on astroph
New Results for GJ1214b:
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• 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)
submitted to ApJ and available on astroph
New Results for GJ1214b:
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NIR Spectroscopy of GJ1214b
107 photons per exposure in K-band
50 ppm on the transit depth
GJ1214
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NIR Spectroscopy of GJ1214b
K-band data
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NIR Spectroscopy of GJ1214b
Parameter decorrelation
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NIR Spectroscopy of GJ1214b
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NIR Spectroscopy of GJ1214b
443 ppm per minute
3.4 times the photon noise
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NIR Spectroscopy of GJ1214b
652 ppm per minute
6.0 times the photon noise
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NIR Spectroscopy of GJ1214b
608 -- 1060 ppm per minute
2.5 times photon noise
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Optical Spectroscopy of GJ1214b
504 – 1432 ppm per minute
1.3 times the photon noise
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Broadband data for GJ1214b
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Broadband data for GJ1214b
Our new measurements
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Broadband data for GJ1214b
Re-analyzed previous measurement
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Broadband data for GJ1214b
Spitzer data (Desert et al. 2011)
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Broadband data for GJ1214b
Croll et al. (2011) measurements
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Broadband data for GJ1214b
• No spectral features detected
• Croll et al. (2011) K-band point inconsistent with MMIRS broadband point at 4.1σ
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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
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K-band spectroscopy for GJ1214b
• No spectral features detected
• Confirm results of Crossfield et al. (2011) at lower resolution
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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
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• No spectral features detected
Optical spectroscopy for GJ1214b
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• 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
Optical spectroscopy for GJ1214b
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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
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Observation schematic
spectrum
12” x 30” slits
Appro
x 5’