The Broadband Infrared Emission Spectrum of the Exoplanet HD 189733b

Charbonneau, David; Knutson, Heather A.; Barman, Travis; Allen, Lori; Mayor, M.; Megeath, S. Thomas; Queloz, D.; Udry, S.

doi:10.1086/591635

Cited by 290 publications

(388 citation statements)

References 77 publications

Supporting

Mentioning

353

Contrasting

Order By: Relevance

“…This means the star is bright and the eclipses are relatively deep yielding favorable signal-to-noise ratio (SNR). As such, HD 189733b represents a "Rosetta Stone" for the field of exoplanetology with one of the highest SNR secondary eclipses (Deming et al 2006;Charbonneau et al 2008), phase-curve observations (Knutson et al 2007(Knutson et al , 2009(Knutson et al , 2012 and, consequently, numerous atmospheric characterizations (e.g., Grillmair et al 2007;Pont et al 2007;Tinetti et al 2007;Redfield et al 2008;Swain et al 2008;Madhusudhan & Seager 2009;Désert et al 2009;Deroo et al 2010;Sing et al 2011;Gibson et al 2011;Huitson et al 2012). Although HD 189733b's atmospheric models are in qualitative agreement with observations, important discrepancies remain between simulated and observed light curves as well as between emission spectra (see e.g., Showman et al 2009, Figs.…”

Section: Introductionmentioning

confidence: 99%

Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b

Wit

Gillon

Demory

et al. 2012

A&A

142

163

View full text Add to dashboard Cite

Context. Mapping distant worlds is the next frontier for exoplanet infrared (IR) photometry studies. Ultimately, constraining spatial and temporal properties of an exoplanet atmosphere (e.g., its temperature) will provide further insight into its physics. For tidallylocked hot Jupiters that transit and are eclipsed by their host star, the first steps are now possible. Aims. Our aim is to constrain an exoplanet's (1) shape, (2) brightness distribution (BD) and (3) system parameters from its phase curve and eclipse measurements. In particular, we rely on the secondary-eclipse scanning which is obtained while an exoplanet is gradually masked by its host star. Methods. We use archived Spitzer/IRAC 8-µm data of HD 189733 (six transits, eight secondary eclipses, and a phase curve) in a global Markov chain Monte Carlo (MCMC) procedure for mitigating systematics. We also include HD 189733's out-of-transit radial velocity (RV) measurements to assess their incidence on the inferences obtained solely from the photometry. Results. We find a 6σ deviation from the expected occultation of a uniformly-bright disk. This deviation emerges mainly from a large-scale hot spot in HD 189733b's atmosphere, not from HD 189733b's shape. We indicate that the correlation of the exoplanet orbital eccentricity, e, and BD ("uniform time offset") does also depend on the stellar density, ρ , and the exoplanet impact parameter, b ("e-b-ρ -BD correlation"). For HD 189733b, we find that relaxing the eccentricity constraint and using more complex BDs lead to lower stellar/planetary densities and a more localized and latitudinally-shifted hot spot. We, therefore, show that the light curve of an exoplanet does not constrain uniquely its brightness peak localization. Finally, we obtain an improved constraint on the upper limit of HD 189733b's orbital eccentricity, e ≤ 0.011 (95% confidence), when including HD 189733's RV measurements. Conclusions. Reanalysis of archived HD 189733's data constrains HD 189733b's shape and BD at 8 µm. Our study provides new insights into the analysis of exoplanet light curves and a proper framework for future eclipse-scanning observations. In particular, observations of the same exoplanet at different wavelengths could improve the constraints on HD 189733's system parameters while ultimately yielding a large-scale time-dependent 3D map of HD 189733b's atmosphere. Finally, we discuss the perspective of extending our method to observations in the visible (e.g., Kepler data), in particular to better understand exoplanet albedos.

show abstract

Section: Introductionmentioning

confidence: 99%

Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b

Wit

Gillon

Demory

et al. 2012

A&A

142

163

View full text Add to dashboard Cite

show abstract

“…On a large scale, the transmission spectra of hot-Jupiters seem to be dominated by the signature of water vapour (Barman 2007(Barman , 2008Beaulieu et al 2010;Burrows et al 2007Burrows et al , 2008Burrows et al , 2010Charbonneau et al 2008;Grillmair et al 2008;Knutson et al 2008;Madhusudhan and Seager (2009);Tinetti et al 2007aTinetti et al , 2007b, whereas warm Neptunes, such as GJ 436b and GJ 3470b, are expected to be methane-rich (Beaulieu et al 2011;Fukui et al 2013). The analysis of GJ 436b cannot be considered conclusive, though, given the activity of the star (Knutson et al 2011) and the lack of spectroscopic data: only photometric data, often recorded at different times, are available for this target.…”

Section: Primary Transit Observationsmentioning

confidence: 99%

“…Agol et al 2010;Beaulieu et al 2008Beaulieu et al , 2010Beaulieu et al , 2011Brown 2001;Burke et al 2010;Charbonneau et al 2005Charbonneau et al , 2008Deming et al 2013;Désert et al 2011;Grillmair et al 2008;Knutson et al 2007;Machalek et al 2009;Pont et al 2008;Sing et al 2011a;Stevenson et al 2010;Swain et al 2008Swain et al , 2009b. Parametric models approximate systematic noise via the use of auxiliary information of the instrument, the so-called optical state vectors, which often include the positional drifts of the star on the detector, the focus and the detector temperature changes, the positional angles of the telescope on the sky etc.…”

Section: Primary Transit Observationsmentioning

confidence: 99%

Spectroscopy of planetary atmospheres in our Galaxy

Tinetti

Encrenaz

Coustenis

2013

Astron Astrophys Rev

130

111

View full text Add to dashboard Cite

About 20 years after the discovery of the first extrasolar planet, the number of planets known has grown by three orders of magnitude, and continues to increase at neck breaking pace. For most of these planets we have little information, except for the fact that they exist and possess an address in our Galaxy. For about one third of them, we know how much they weigh, their size and their orbital parameters. For less than 20, we start to have some clues about their atmospheric temperature and composition. How do we make progress from here?We are still far from the completion of a hypothetical Hertzsprung-Russell diagram for planets comparable to what we have for stars, and today we do not even know whether such classification will ever be possible or even meaningful for planetary objects. But one thing is clear: planetary parameters such as mass, radius and temperature alone do not explain the diversity revealed by current observations. The chemical composition of these planets is needed to trace back their formation history and evolution, as happened for the planets in our Solar System. As in situ measurements are and will remain off-limits for exoplanets, to study their chemical composition we will have to rely on remote sensing spectroscopic observations of their gaseous envelopes.

show abstract

“…On a large scale, the IR transit and eclipse spectra of hot-Jupiters seem to be dominated by the signature of water vapour (e.g. [10,21,26,34,38,47,48,50,54,74,91,111,[159][160][161][168][169][170][171]), similarly, the atmosphere of hot-Neptune HAT-P-11b appears to be water-rich [67]. The data available for other warm Neptunes, such as GJ 436b, GJ 3470b are suggestive of cloudy atmospheres and do not always allow a conclusive identification of their composition [22,65,70,88,117,156].…”

Section: Exoplanets Todaymentioning

confidence: 99%

“…These were achieved with Spitzer [107]. See also [52,56,121] All three techniques have already been used very successfully from the optical to the near-and mid-infrared, showing molecular, atomic absorption and Rayleigh scattering features in transmission [21,25,36,47,48,55,86,89,101,132,147,148,160,[168][169][170]182] and/or emission spectra [38,74,91,156,159,161,171] of a few of the brightest and hottest transiting gas giants, using the Hubble and Spitzer space telescopes. In addition, infrared phase variations have been measured at several wavelengths using Spitzer, showing only a relatively small temperature difference (300 K) between the planet's day and night-side -implying an efficient redistribution of the absorbed stellar energy [86].…”

Section: Transits Eclipses and Phase-curvesmentioning

confidence: 99%

The EChO science case

et al. 2015

View full text Add to dashboard Cite

The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune-all unknown in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample within its 4-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allows us to measure atmospheric signals from the planet at levels of at least 10 −4 relative to the star. This can only be achieved in conjunction with a carefully designed stable payload and satellite platform. It is also necessary to provide broad instantaneous wavelength coverage to detect as many molecular species as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength coverage of at least 0.55 to 11 μm with a goal of covering from 0.4 to 16 μm. Only modest spectral resolving power is needed, with R~300 for wavelengths less than 5 μm and R~30 for wavelengths greater than this. spectroscopy technique means that no spatial resolution is required. A telescope collecting area of about 1 m 2 is sufficiently large to achieve the necessary spectro-photometric precision: for the Phase A study a 1.13 m 2 telescope, diffraction limited at 3 μm has been adopted. Placing the satellite at L2 provides a cold and stable thermal environment as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. EChO has been conceived to achieve a single goal: exoplanet spectroscopy. The spectral coverage and signal-to-noise to be achieved by EChO, thanks to its high stability and dedicated design, would be a game changer by allowing atmospheric composition to be measured with unparalleled exactness: at least a factor 10 more precise and a factor 10 to 1000 more accurate tha...

show abstract

The Broadband Infrared Emission Spectrum of the Exoplanet HD 189733b

Cited by 290 publications

References 77 publications

Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b

Towards consistent mapping of distant worlds: secondary-eclipse scanning of the exoplanet HD 189733b

Spectroscopy of planetary atmospheres in our Galaxy

The EChO science case

Contact Info

Product

Resources

About