1. Exoplanet Transit Spectroscopy February 7, 2014 Avi M. Mandell NASA GSFC Collaborators: Korey Haynes Evan Sinukoff Drake Deming Adam Burrows Nikku Madhusudhan Mark Clampin Don Lindler Natasha Batalha Heather Knutson (others as well) Spectroscopy of Water and Organics in Exoplanet Atmospheres: First Detections and What the Future Holds

2. Exoplanet Transit Spectroscopy February 7, 2014 Henry et al. 1999 What is a Exoplanet Transit?

3. Exoplanet Transit Spectroscopy February 7, 2014 How Do We Learn About the Atmospheres of Transiting Planets? Exoplanet transits provide the opportunity to probe the absorption in a planet’s atmosphere –The more absorption, the deeper the depth of the transit… but absorption depends on abundance, temperature, optical depth –As starlight passes through the atmosphere of a planet, atoms and molecules absorb at different wavelengths Planet Cross-Section

4. Exoplanet Transit Spectroscopy February 7, 2014 HST / WFC3 Grism Spectroscopy: Resolving Molecular Absorption Wavelength range (1.1 – 1.7 μm) samples water bands at 1.15 and 1.4 μm as well as several hydrocarbons and continuum regions on either side Can answer major questions about temperature and chemistry But at LOW resolution over a NARROW bandpass, degeneracies still remain!

5. Exoplanet Transit Spectroscopy February 7, 2014 Deming et al. Program (Cycles 18 & 19) Large collaboration focused on hot giant exoplanets Sample of 16 objects A number of planets may have upper-atmosphere temperature inversions or high C/O ratios We started with several interesting (and outlying) cases: WASP-12: Very hot, first possible carbon- rich exoplanet, but results now in dispute WASP-17: Ultra-low density, retrograde orbit WASP-19: Shortest-period planet known (P ~ 19 hr) but no temperature inversion WASP-33: Very hot and massive, orbiting an A-type star, possibly carbon-rich CoRoT-1 b CoRoT-2 b HAT-P-7 b HAT-P-12 b HAT-P-13 b HD189733 b HD209458 b TrES-2 b TrES-3 b TrES-4 b WASP-4 b WASP-12 b WASP-17 b WASP-18 b WASP-19 b XO-1 b WASP-33 b List of Observed Planets WASP-19 WASP-12 WASP-17 WASP-4 WASP-33 Transits Eclipses

6. Exoplanet Transit Spectroscopy February 7, 2014 Transit Spectra Analysis: Systematics Removal Through Self-Calibration 1. We used the divide-oot method (Berta et al. 2012) to fit the band- integrated light curve 2. We subtracted the model from the raw light curve to obtain the residual systematic variation; additional trends due to spectral drift were also measured 3. We created a model for each wavelength bin, with a scaling parameter for each possible systematic trend in the data and an overall visit-long slope WASP-12 WASP-17 WASP-19 WASP-17

7. Exoplanet Transit Spectroscopy February 7, 2014 Primary Result: Amplitude of water absorption band is lower than expected (based on previous Spitzer obs.) Due to either: 1.An unexplained haze layer that increases the continuum opacity below a certain altitude 2.Less water due to non-solar abundances (T ~ 2500K) (T ~ 2900K) (T ~ 2000K)

8. Exoplanet Transit Spectroscopy February 7, 2014 1.A 2.2 3.Cooler planets seem to show well-defined spectral features, while hotter planets are ambiguous… NEED MORE PLANETS and MORE SPECTRAL COVERAGE Primary Result: Amplitude of water absorption band is lower than expected (based on previous Spitzer obs.) Due to either: 1.An unexplained haze layer that increases the continuum opacity below a certain altitude 2.Less water due to non-solar abundances (T ~ 2000K) (T ~ 1800K) (T ~ 1700K)

9. Exoplanet Transit Spectroscopy February 7, 2014 Eclipse Spectra Analysis: We again used the divide-oot method to fit the band-integrated light curve, WASP-33 presents additional complications due to Delta Scuti oscillations in the parent star Band-integrated eclipse depths are much more uncertain than the transit measurements due to the low eclipse-to-noise ratio WASP-4 is especially problematic due to very little temporal coverage during eclipse

10. Exoplanet Transit Spectroscopy February 7, 2014 T plan ~ 2200K WASP-4 Preliminary Result: WFC3 data appear to match up with the thermal-inversion atmosphere model from Beerer et al. 2011; however, a blackbody seems to be an even better fit (T ~ 2500K) (T ~ 2900K) The spectrum seems to show a slight peak at 1.4 microns, indicative of a possible strong inversion However, this model does not match the Spitzer data well A blackbody with T plan = 2200 K provides an excellent fit to all existing data

11. Exoplanet Transit Spectroscopy February 7, 2014 WASP-12 Preliminary Result: WFC3 data appear to support a carbon-rich model, showing no sign of the expected deep absorption band. However, as noted in Crossfield et al. 2012, correcting the Spitzer data for the nearby companions leads to an isothermal interpretation

12. Exoplanet Transit Spectroscopy February 7, 2014 WASP-33 Preliminary Result: WFC3 data strongly support a model with no thermal inversion, and models that are carbon-rich fit better Further modeling is required to determine whether we can break degeneracies between temperature and composition

13. Exoplanet Transit Spectroscopy February 7, 2014 JWST will provide sensitivity gains of more than an order of magnitude We are preparing to adapt our WFC3 analysis pipeline to JWST, based on current instrument models by M. Clampin & D. Lindler Simulated Hot Super-Earth (T eq ~ 500K) around an M-star at 30 pc Simulated Habitable Super-Earth (T eq ~ 300K) around an M-star at 20 pc H 2 O Abs. H 2 O Abs. CO 2 Abs. Deming et al. 2009 The Future of Space-Based Characterization: JWST (of course) JWST/NIRSPEC Simulations For hot Jupiters, the real test lies in which instruments and filters to use in order to MOST EFFICIENTLY constrain the atmospheric parameters JWST Wavelength Coverage & Resolution H2OH2O CH 4 H2OH2O H2OH2O CO CO 2 CO CH 4 HCN C2H2C2H2 CO

14. Exoplanet Transit Spectroscopy February 7, 2014 JWST NIRSPEC Simulator 1.Begins with In- transit and Out- of-transit model 2.Maps onto pixel space 3.Convolves with PSF, multiplies by PRF 4.Add noise sources  Zodiacal and stray light  Flat field errors  Poisson and read noise  Spacecraft jitter and drift Images from Don Lindler, results from Batalha et al. (JWST White Paper) 14 pc, V = 15 4.5 pc H 2 O & CH 4 M-type host star 4 M Earth planet 25 transits

15. Exoplanet Transit Spectroscopy February 7, 2014 Pre-JWST Characterization: Low-Cost NIR Spectroscopy from a Balloon? Ultra-long duration (ULD) balloon platforms offer the potential for long- term, stable monitoring of transiting planets above almost all telluric contamination –As low as 1 - 2% of an equally-capable space mission Test flight using the Wallops Arc Second Pointer (WASP) gondola system planned for September 2014 –Use of existing and off-the-shelf parts will allow us to benchmark the current limits for stability and thermal control

16. Exoplanet Transit Spectroscopy February 7, 2014 Conclusions The WFC3 instrument on HST has now been validated as a reliable platform for high-precision exoplanet transit observations Observations of Hot Jupiters are revealing unexpected mysteries –Hazes and/or aerosols may be common, but vary with planet properties –Thermal emission measurements suggest blackbody emission at NIR wavelengths may be ubiquitous; unclear if this is due to thermal or compositional factors, and why it appears so uniform Increased S/N and larger wavelength coverage (combining Spitzer, HST and ground) will be necessary to grapple with these questions –JWST will clearly change the landscape dramatically, but observing time will be precious, so we must pre-select targets for follow-up

17. Exoplanet Transit Spectroscopy February 7, 2014 Questions?