1. JPL-CITParis 2008 On NIR HST Spectro-photometry of Transiting Exo-planets Vasisht, Swain, Deroo, Chen, Wayne (JPL), Tinetti (UCL), Yung (CIT), Angerhausen (PIUK), Bouwman (MPIA), Deming (GSFC)

2. Outline  Motivation for NIR objective mode, time-resolved spectroscopy  Instrumental issues > General issues confronting shot-noise limited spectroscopy > Hubble specific limitations  Modeling and removal of instrumental limitations  Spectroscopy of the emergent flux from HD189733b (Swain, Vasisht, Tinetti, Deroo, Yung et al., accepted ApJL) JPL-CITParis 2008

3. Spectroscopy with NICMOS  Slitless Grism spectrograph between 0.8- 2.5 microns  Camera 3 –Coverage by 3 grisms located in filter wheel –R = 200 native spectral resolution –Camera 3 is severely under-sampled at 0.2”/pixel (~λ/D @ 2 um, 52” FOV)  Exoplanet datasets have now been acquired with all grisms –G141 on HD 209548b (Brown et al. in 2005, unpublished) JPL-CITParis 2008

4. Scientific Rationale  NIR Emission Spectroscopy (λ ~1-2.5 um; Spitzer 3-30 um) –Observable: Falling but favorable flux contrast (< 3 um) –Energetically Important: Maximum νF ν (for emergent flux) –Decreased stellar shot-noise –NIR photosphere at greater pressure depths (0.1-1 bar) –Molecular activity: ro-vib bands of major species  Again some of the same advantages apply for transmission spectroscopy –Reduced opacity from small particle scattering JPL-CITParis 2008

5. Hot, Cold or Cloudy JPL-CITParis 2008 Seager et al. 2005 Homogenous clouds Hot T = 1750 K dayside reradiation

6. Active (common) C,N,O molecules JPL-CITParis 2008 Lodders & Fegley 2002

7. JPL-CITParis 2008 Hubeny & Burrows 2008

8.  Molecular spectroscopy -> atmospheric physics –Atmospheres are a window to planetary composition, may have clues to evolutionary history –History of the planet can give rise to a range in core sizes, heavy element abundances, and abundance ratios –Relative fractions of refractory and volatile materials should reflect upon  Parent star abundances, history of formation, migration (?) JPL-CITParis 2008

9. JPL-CITParis 2008 Part II – Photometry with HST 1.Detector anomalies 2.Optical anomalies Photometric systematic noise

10. JPL-CITParis 2008 NICMOS Detector Effects  Stress induced structure in the response  Pixel-to-Pixel stochastic response variations  Intrapixel structure in the response  T-dependence Figer et al. 2002

11. Large scale structure JPL-CITParis 2008 NIC-3 is under- sampled PAM Defocus provides some “Immunity” This sets R ~ 40 Watch for structure under spectrum. Flats can remove some of this power

12. JPL-CITParis 2008 Small-scale structure and MTF Finger et al. 2000Stiavelli et al.

13. JPL-CITParis 2008 Relative Photometry Evaluate in some statistical fashion

14. JPL-CITParis 2008 Relative Photometry k-space  Variance is integral over spatial frequencies of –Power spectrum of the detector response apodised by  1. Power spectrum of the illumination  2. 1-cos() high pass filter

15. 14/08/2008Paris 2008 1-cos(k dx), dx = 0.1 pix Intrapixel gainPSF Defocused PSF by Ray Tracing: Note this is a PSD Diffraction

16. Implications  Significant substructure in the psf (ILS) –At spatial frequencies of D/λ, D/2λ etc –Due to diffraction –D/λ ~ 1/pixel –Mostly preserved in cross-dispersion axis  Varies with wavelength –For shorter λ, higher spatial frequencies  Can interact with sub-pixel structure JPL-CITParis 2008

17.  Beam wander  In x (spatial) and y (spectral)  Repositioning errors –Filter wheel positioning –Rot. about un-deviated ray  Orbital phase PSF modulation –Proxy (Gaussian FWHM)  Array response variations – QE with temperature –~ 1%/K (2.5 micron), 3%/K (1.5 micron) JPL-CITParis 2008 DISCRETE OFFSETS X, Y, θ, T PERIODIC σ

18.  Biggest headache is image motion  Repositioning errors (Monte Carlo) –δx, δy ~ 0.1 pixel; linear perturbations –δx, δy > 0.25 pixels; large higher order errors (> 10 -4 )  Generally few usable orbits per visit –Adding 2 nd order terms to expansion is problematic JPL-CITParis 2008 dx, dy, dθ dT Σ dσ dI

19. JPL-CITParis 2008

20. JPL-CITParis 2008

21. JPL-CITParis 2008 Orbit 1

22. JPL-CITParis 2008 Other Systematics  Optical effects –Flux-migration between grating-orders  Response of interference filter  Geometrical shadowing by grooves  Woods anomalies

23. JPL-CITParis 2008 Part III – Observations of HD 189733b Part III – Observations of HD 189733b

24. State-Variables HD189733b Paris 2008 angle temperature defocus position

25. Iterative Multivariate Fits JPL-CIT Light curve Design Matrix Model vector Noise

26. JPL-CITParis 2008 Data Modeling-III Raw periodogram Post-fit residuals

27. Lightcurves JPL-CITParis 2008 Broadband 1.5 To 2.5 um K band K band with Common mode Noise removed Final K band Lightcurve

28. HD 189733 (Basic Data)  HD 189733 (K1-K2V) –T ~ 5000 K –19.3 pc –> 0.6 Gyr –Metallicity -0.03 +/- 0.04  HD 189733b (Bouchy et al. 2005) –1.144 MJ, 1.138 RJ –Circular 0.03 AU orbit (2.22 d)  Secondary eclipse observations –Barnes et al. 2007 (dC ~ 4x10 -4 ) JPL-CITParis 2008 J. Schneider, Ex. Enc.

29. Spectral Modeling  Retrieval using RT models (Goody & Yung 1989)  Disk-averaged radiative transfer models developed originally for Earthshine, Mars  (Tinetti et al. 2006, 2007)  P-T profiles (Barman et al. 2008, Burrows et al. 2008)  Photochemistry (Yung, Liang)  Layer-by-layer (log P between -6 and 0) –Input T-P profiles –Chemical profiles (simple constant VMR) –Opacities (T, ρ); Cloudless. JPL-CITParis 2008

30. JPL-CITParis 2008 HD189733b NIR Contrast Spectrum

31. 14/08/2008 Contrast Spectrum Components

32. Paris 2008 Showman et al. 2008Comparison with radiation-hydrodynamics models Planet brightest away from anti-stellar point Knutson et al. 2007

33. JPL-CITParis 2008 Retrieval Results  Dayside emission (subsolar) –Water (0.1-1 10 -4 ) –Carbon monoxide (thermochemically very stable at these P,Ts; CO=CH4 T=1100K at 1 bar)  Also inferred from IRAC photometry (Charbonneau et al. 2008)  10 -4 –Carbon dioxide (trace concentration 10 -6 )  CO+H2O CO2+H2 (thermochemical in a CO field; Lodders & Fegley 2002)  CO+OH CO2+H (photochemical pathway) –Methane upper limit (10 -7 ) –Significant residuals at the blue end of the spectrum

34. JPL-CITParis 2008 Abundances  C/O is high and not well constrained (cloudless model) –0.5 to 10  Solar 0.48 (Anders & Grevesse 1989) Favor lower values because high C/O implies disappearing water in CO field –Terminator (Swain, Vasisht, Tinetti 2008)  Lower pressure depths  Methane abundance is higher (CO < CH4)  Water 5.10 -4

35. In Summary JPL-CITParis 2008 Little evidence for … Hot Jovians not as “hot” as … good hot Curry !.

36. Chemistry  Hot less dense atmospheres are more likely to show abundant CO (and CO2 at lower T), while cooler, denser ones show more abundant methane.  At 1 bar the CO=CH4 boundary is at T = 1125 K.  C/O atomic ratio is 0.48 (solar) 14/08/2008Exeter Exoplanet Workshop

37. JPL-CITParis 2008

38. JPL-CITParis 2008 Pont et al. 2008

39. JPL-CITParis 2008 F. Pont et al. 2008

40. Carbon & Oxygen Chemistry  Major carbon bearing gases in a solar composition gas of given metallicity are generally CH4, CO and/or CO2 depending on T and P. 14/08/2008Exeter Exoplanet Workshop