Spectroscopy of Water and Organics in
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Spectroscopy of Water and Organics in Exoplanet Atmospheres: First Detections and What the Future Holds. Avi M. Mandell NASA GSFC Collaborators :. Korey Haynes Evan Sinukoff Drake Deming Adam Burrows Nikku Madhusudhan Mark Clampin Don Lindler Natasha Batalha Heather Knutson

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Avi m mandell nasa gsfc collaborators

Spectroscopy of Water and Organics in Exoplanet Atmospheres:

First Detections and What the Future Holds

Avi M. Mandell

NASA GSFC

Collaborators:

Korey Haynes

Evan Sinukoff

Drake Deming

Adam Burrows

NikkuMadhusudhan

Mark Clampin

Don Lindler

Natasha Batalha

Heather Knutson

(others as well)


Avi m mandell nasa gsfc collaborators

Henry et al. 1999

  • What is a

  • ExoplanetTransit?


How do we learn about the atmospheres of transiting planets

How Do We Learn About the Atmospheresof Transiting Planets?

  • As starlight passes through the atmosphere of a planet, atoms and molecules absorb at different wavelengths

  • The more absorption, the deeper the depth of the transit… but absorption depends on abundance, temperature, optical depth

  • Exoplanet transits provide the opportunity to probe the absorption in a planet’s atmosphere

Planet Cross-Section


Avi m mandell nasa gsfc collaborators

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!


Avi m mandell nasa gsfc collaborators

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

List of Observed Planets

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

WASP-12

WASP-33

WASP-19

WASP-4

WASP-17

Transits

Eclipses


Avi m mandell nasa gsfc collaborators

Transit Spectra Analysis:

SystematicsRemoval Through Self-Calibration

We used the divide-ootmethod (Berta et al. 2012) to fit the band-integrated light curve

We subtracted the model from the raw light curve to obtain the residual systematic variation; additional trends due to spectral drift were also measured

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-17

WASP-19


Avi m mandell nasa gsfc collaborators

  • PrimaryResult: Amplitude of water absorption band islower than expected (based on previous Spitzer obs.)

    • Due to either:

    • Anunexplained haze layer that increases the continuum opacity below a certain altitude

    • Less water due to non-solar abundances

(T ~ 2900K)

(T ~ 2000K)

(T ~ 2500K)


Avi m mandell nasa gsfc collaborators

  • Primary Result: Amplitude of water absorption band is lower than expected (based on previous Spitzer obs.)

    • Due to either:

    • Anunexplained haze layer that increases the continuum opacity below a certain altitude

    • Less water due to non-solar abundances

(T ~ 2000K)

  • A

  • 2

  • Cooler planets seem to show well-defined spectral features, while hotter planets are ambiguous…

    • NEED MORE PLANETS and MORE SPECTRAL COVERAGE

(T ~ 1800K)

(T ~ 1700K)


Avi m mandell nasa gsfc collaborators

Eclipse Spectra Analysis:

  • We again used the divide-ootmethod 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


Avi m mandell nasa gsfc collaborators

  • WASP-4 PreliminaryResult: WFC3 data appear to match up with the thermal-inversionatmosphere model from Beerer et al. 2011; however, a blackbody seems to be an even better fit

(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 Tplan = 2200 K provides an excellent fit to all existing data

Tplan~ 2200K

(T ~ 2500K)


Avi m mandell nasa gsfc collaborators

  • 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


Avi m mandell nasa gsfc collaborators

  • 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


Avi m mandell nasa gsfc collaborators

The Future of Space-Based Characterization:

JWST (of course)

  • 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

  • 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

JWST/NIRSPEC Simulations

CO2

Abs.

H2O

Abs.

Simulated Hot Super-Earth

(Teq ~ 500K) around an

M-star at 30 pc

H2O

Abs.

CH4

H2O

C2H2

CO

Simulated

Habitable

Super-Earth

(Teq ~ 300K)

around an

M-star at 20 pc

HCN

CH4

CO

CO2

H2O

CO

H2O

Deming et al. 2009


Jwst nirspec simulator

JWST NIRSPEC Simulator

  • Begins with In-transit and Out-of-transit model

  • Maps onto pixel space

  • Convolves with PSF, multiplies by PRF

  • Add noise sources

    • Zodiacal and stray light

    • Flat field errors

    • Poisson and read noise

    • Spacecraft jitter and drift

14 pc, V = 15

4.5 pc

M-type host star

4 MEarth planet

25 transits

H2O & CH4

Images from Don Lindler, results from Batalha et al. (JWST White Paper)


Pre jwst characterization low cost nir spectroscopy from a balloon

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


Conclusions

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


Avi m mandell nasa gsfc collaborators

Questions?


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