SEARCH FOR CARBON MONOXIDE IN THE ATMOSPHERE OF THE TRANSITING EXOPLANET HD 189733b

By J. D'esert, A. Lecavelier des Etangs, G. Hébrard, D. Sing, David Ehrenreich, R. Ferlet, A. Vidal-Madjar. 2009

144 citations recorded by the source corpus.

Water, methane, and carbon monoxide are expected to be among the most abundant molecules besides molecular hydrogen in the hot atmosphere of close-in extrasolar giant planets. Atmospheric models for these planets predict that the strongest spectrophotometric features of those molecules are located at wavelengths ranging from 1 to 10 μm making this region of particular interest. Consequently, transit observations in the mid-infrared (mid-IR) allow the atmospheric content of transiting planets to be determined. We present new primary transit observations of the hot-Jupiter HD 189733b, obtained simultaneously at 4.5 and 8 μm with the Infrared Array Camera onboard the Spitzer Space Telescope. Together with a new refined analysis of previous observations at 3.6 and 5.8 μm using the same instrument, we are able to derive the system parameters, including planet-to-star radius ratio, impact parameter, scale of the system, and central time of the transit from fits of the transit light curves at these four wavelengths. We measure the four planet-to-star radius ratios, to be (Rp/R⋆)3.6 μm = 0.1545 ± 0.0003, (Rp/R⋆)4.5 μm = 0.1557 ± 0.0003, (Rp/R⋆)5.8 μm = 0.1547 ± 0.0005, and (Rp/R⋆)8 μm = 0.1544 ± 0.0004. The high accuracy of the planet radii measurement allows the search for atmospheric molecular absorbers. Contrary to a previous analysis of the same data set, our study is robust against systematics and reveals that water vapor absorption at 5.8 μm is not detected in this photometric data set. Furthermore, in the band centered around 4.5 μm we find a hint of excess absorption with an apparent planetary radius ΔRp/R* =  0.00128 ± 0.00056 larger (2.3σ) than the one measured simultaneously at 8 μm. This value is 4σ above what would be expected for an atmosphere where water vapor is the only absorbing species in the near-IR. This shows that an additional species absorbing around 4.5 μm could be present in the atmosphere. Carbon monoxide (CO) being a strong absorber at this wavelength is a possible candidate and this may suggest a large CO/H2O ratio between 5 and 60.

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/1f4920000ba56af84c42e0c1483631022d577372

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In Astronomy and Astrophysics

1. Jon Fortney
2. N. Madhusudhan
3. D. Charbonneau
4. Sara Seager
5. A. Showman
6. D. Deming
7. J. Winn
8. H. Knutson

In Atmospheric Science

1. M. Marley
2. Jon Fortney
3. N. Madhusudhan
4. A. Showman
5. R. Freedman
6. V. Parmentier
7. D. Sing
8. J. D'esert

Citations in the corpus

• C/O RATIO AS A DIMENSION FOR CHARACTERIZING EXOPLANETARY ATMOSPHERES (2012, background): “…(e.g. Charbonneau et al. 2002, Vidal Madjar et al. 2004, Tinetti et al. 2007, Swain et al. 2008, 2012; cf Gibson et al. 2011, Bueaulieu et al. 2008, Desert et al. 2009, Redfield et al. 2008, Madhusudhan & Seager 2009, Sing et al. 2011, Bean et al. 2010, Crossfield et al. 2012, Berta et al. 2012),…”
• TRANSMISSION SPECTRA OF THREE-DIMENSIONAL HOT JUPITER MODEL ATMOSPHERES (2009, methodology): “In Figure 8 we compare transmission spectra calculated at 1,3, 10, and 30× solar, for the 1D model, with the corresponding correct MMWs, to the Désert et al. (2009) data.”
• HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering (2014, background): “…model of the form: f(t) = a0 + a1x+ a2x 2 + a3y + a4y 2 + a5xy + a6t (3) where f(t) is the stellar flux as a function of time, x and y are the positions of the stellar centroid on the detector, t is time and a0 to a6 are the free parameters in the fit (Désert et al. 2009; Todorov et al. 2013).”
• A chemical model for the atmosphere of hot Jupiters (2012, background): “…et al. 2008; Swain et al. 2009b, for emission spectrum) and (Knutson et al. 2007, 2009; Swain et al. 2008b; Beaulieu et al. 2008; Sing et al. 2009; Désert et al. 2009; Agol et al. 2010, for transmission spectrum), but we do not discuss the agreement between observations and synthetic spectra, as…”
• KEPLER-18b, c, AND d: A SYSTEM OF THREE PLANETS CONFIRMED BY TRANSIT TIMING VARIATIONS, LIGHT CURVE VALIDATION, WARM-SPITZER PHOTOMETRY, AND RADIAL VELOCITY MEASUREMENTS (2011, methodology): “To obtain an estimate of the correlated and systematic errors (Pont et al. 2006) in our measurements, we use the residual permutation bootstrap, or “Prayer Bead”, method as described in Désert et al. (2009).”
• WATER VAPOR IN THE SPECTRUM OF THE EXTRASOLAR PLANET HD 189733b. I. THE TRANSIT (2014, background): “FromSpitzerIRAC transit photometry at 3.6µm, 5.8 µm, and 8µm, Tinetti et al. (2007) reported evidence of water vapor in the atmosphere of HD 189733b (but cf. Désert et al. 2009).”
• 3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, methodology): “…obtain planet-star radius ratios of 0.15511±0.00020 at 3.6 µm and 0.15580±0.00019 at 4.5 µm, which we compare to previously published values of 0.1545± 0.0003 at 3.6 µm and 0.1557± 0.0003 at 4.5 µm from Désert et al. (2009), and 0.155660.00011−0.00024 at 3.6 µm from Désert et al. (2011a).”
• LOW FALSE POSITIVE RATE OF KEPLER CANDIDATES ESTIMATED FROM A COMBINATION OF SPITZER AND FOLLOW-UP OBSERVATIONS (2015, methodology): “Désert et al. (2009) describes the method used to produce photometric time series in each channel from the BCD files.”
• Hubble Space Telescope hot Jupiter transmission spectral survey: a detection of Na and strong optical absorption in HAT-P-1b (2013, background): “In the case of HAT-P-1b, when two or more signatures are present, the relative abundance can be measured (Lecavelier Des Etangs et al. 2008; Désert et al. 2009; Huitson et al. 2012).”
• ROTATION AND WINDS OF EXOPLANET HD 189733 b MEASURED WITH HIGH-DISPERSION TRANSMISSION SPECTROSCOPY (2015, background): “Lowresolution observations of the near-infrared spectrum of HD 189733 b point towards the presence of water and possibly carbon monoxide (Barman 2007; Beaulieu et al. 2008; Charbonneau et al. 2008; Désert et al. 2009).”
• Exoplanet Atmospheres: Physical Processes (2010, background): “One group (Tinetti et al. 2007 and Beaulieu et al. 2008) finds a deeper transit at 5.8 µm than another group (Desert et al. 2009).”
• Evaporation of the planet HD 189733b observed in H I Lyman-α (2010, background): “It has been tentatively proposed that CO molecules can explain the excess absorption seen at 4.5 µm (Charbonneau et al. 2008; Désert et al. 2009).”
• Optimal estimation retrievals of the atmospheric structure and composition of HD 189733b from secondary eclipse spectroscopy (2011, methodology): “…upper layers of an exoplanetary atmosphere, have been measured in the near-, mid- and farinfrared (NIR, MIR and FIR, respectively) by both theHubble Space Telescope (HST ) (Swain et al. 2008; Sing et al. 2009) andSpitzer telescope (Tinetti et al. 2007a; Beaulieu et al. 2008; Désert et al. 2009).”
• Temperature–pressure profile of the hot Jupiter HD 189733b from HST sodium observations: detection of upper atmospheric heating (2012, methodology): “We used Equation (6) along with σH2O = 2 × 10−20 cm2 at a wavelength of 8 µm (Désert et al. 2009) and a radius for the water feature at 8 µm of RP/R⋆ = 0.15531 (Agol et al. 2010).”
• Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b (2013, background): “From Spitzer data the presence of CO was already suspected (Barman 2008; Désert et al. 2009) , although more wider scans of the parameter space revealed no useful constraints on CO based on the Spitzer secondary eclipse data alone (Madhusudhan & Seager 2009).”
• Detection of water absorption in the day side atmosphere of HD 189733 b using ground-based high-resolution spectroscopy at 3.2 μm (2013, background): “…latter two spectral features with both systematics and the possible haze being proposed as the causes of conflicting results at different wavelengths (Grillmair et al. 2007; Ehrenreich et al. 2007; Désert et al. 2009; Sing et al. 2009; Gibson et al. 2011; Mandell et al. 2011; Gibson et al. 2012).”
• THE FLAT TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ1214b FROM WIDE FIELD CAMERA 3 ON THE HUBBLE SPACE TELESCOPE (2011, background): “…of the hot Jupiter HD189733b, where the uniform decrease in transit depth from 0.3 to 1 µm (Pont et al. 2008; Lecavelier Des Etangs et al. 2008; Sing et al. 2011) and perhaps to as far as 3.6 µm (see Sing et al. 2009; Désert et al. 2009) has been convincingly attributed to a small particle haze.”
• Temporal variations in the evaporating atmosphere of the exoplanet HD 189733b (2012, background): “In these data, the transit depth for the total flux of the whole Lyman-α line is 2.9±1.4%, which agrees with the 2.4% transit depth of the planet body alone as seen from the visible to the near-infrared (Désert et al. 2009, 2011; Sing et al. 2011).”