Temperature–pressure profile of the hot Jupiter HD 189733b from HST sodium observations: detection of upper atmospheric heating

By C. Huitson, D. Sing, A. Vidal-Madjar, Gilda E. Ballester, A. D. Étangs, J. D'esert, F. Pont. 2012

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We present transmission spectra of the hot Jupiter HD 189733b taken with the Space Telescope Imaging Spectrograph (STIS) aboard Hubble Space Telescope (HST). The spectra cover the wavelength range 5808–6380 A with a resolving power of R= 5000. We detect absorption from the Na i doublet within the exoplanet’s atmosphere at the 9σ confidence level within a 5 A band (absorption depth 0.09 ± 0.01 per cent) and use the data to measure the doublet’s spectral absorption profile. We detect only the narrow cores of the doublet. The narrowness of the feature could be due to an obscuring high-altitude haze of an unknown composition or a significantly sub-solar Na i abundance hiding the line wings beneath an H2 Rayleigh signature. These observations are consistent with previous broad-band spectroscopy from Advanced Camera for Surveys (ACS) and STIS, where a featureless spectrum was seen. We also investigate the effects of starspots on the Na i line profile, finding that their impact is minimal and within errors in the sodium feature. We compare the spectral absorption profile over 5.5 scale heights with model spectral absorption profiles and constrain the temperature at different atmospheric regions, allowing us to construct a vertical temperature profile. We identify two temperature regimes: a 1280 ± 240 K region derived from the Na i doublet line wings corresponding to altitudes below ∼500 km, and a 2800 ± 400 K region derived from the Na i doublet line cores corresponding to altitudes from ∼500 to 4000 km. The zero altitude is defined by the white-light radius of RP/R★= 0.15628 ± 0.00009. The temperature rises with altitude, which is likely evidence of a thermosphere. The absolute pressure scale depends on the species responsible for the Rayleigh signature and its abundance. We discuss a plausible scenario for this species, a high-altitude silicate haze and the atmospheric temperature–pressure profile that results. In this case, the high-altitude temperature rise for HD 189733b occurs at pressures of 10−5 to 10−8 bar.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/b623510c400f576db4e0607167703fce80c20e8a

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Citations in the corpus

Spectrally resolved detection of sodium in the atmosphere of HD 189733b with the HARPS spectrograph (2015, methodology): “Furthermore, the analysis of the spacebased detection of the sodium signature of these two planets by Sing et al. (2008b), Vidal-Madjar et al. (2011), and Huitson et al. (2012), demonstrated the potential of resolving the transmitted stellar light by the planet atmosphere.”
ROTATION AND WINDS OF EXOPLANET HD 189733 b MEASURED WITH HIGH-DISPERSION TRANSMISSION SPECTROSCOPY (2015, background): “…et al. 2010; Jensen et al. 2012) and the prominence of haze (Pont et al. 2008; Sing et al. 2011) masking most of the spectral features in the optical transmission spectrum, except for atomic sodium (Redfield et al. 2008; Huitson et al. 2012; Wyttenbach et al. 2015) and potassium (Pont et al. 2013).”
An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b: detection of atmospheric water and likely absence of TiO (2013, methodology): “…with decreasing wavelength, attributed to a scattering signature similar to that of Rayleigh scattering (Lecavelier Des Etangs et al. 2008; Pont et al. 2008; Sing et al. 2011a), where all but the narrow cores of the lines are obscured (Redfield et al. 2008; Jensen et al. 2011; Huitson et al. 2012).”
HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering (2014, methodology): “To further constrain the pressures and abundances, we model the alkali metal lines following Burrows et al. (2000), Iro et al. (2005), and Huitson et al. (2012).”
Transmission spectral properties of clouds for hot Jupiter exoplanets (2014, background): “Broadband transmission spectra of exoplanets, such as WASP-12b and HD 189733b, show strong scattering in the optical to near-infrared region of the spectrum (Redfield et al. 2008; Huitson et al. 2012).”
3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, background): “…planet; key results include the detection of a highaltitude haze (Pont et al. 2008; Sing et al. 2011) and sodium absorption (Redfield et al. 2008; Huitson et al. 2012) in its visible-light transmission spectrum, as well as more controversial detections of methane, carbon monoxide, and water…”
ExoMol line lists – XVIII. The high-temperature spectrum of VO (2016, background): “There has been considerable recent debate (Spiegel et al. 2009; Fortney et al. 2010; Bowler et al. 2010; Madhusudhan & Seager 2010; Huitson et al. 2012; Spiegel & Burrows 2013; Gibson et al. 2013; Parmentier et al. 2013; Agúndez et al. 2014; Hoeijmakers et al. 2015; Schwarz et al. 2015; Haynes et…”
WATER VAPOR IN THE SPECTRUM OF THE EXTRASOLAR PLANET HD 189733b. I. THE TRANSIT (2014, background): “Secondly, the lack of Na and K features in optical transmission spectra could be explained by either a low metallicity in the atmosphere (Huitson et al. 2012) and/or by condensation of Na and K either in the low-temperature upper atmosphere or on the night side.”
The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint (2017, background): “The thermosphere of an exoplanet is most sensitively probed by the Na line core (e.g. Huitson et al. 2012).”
A chemical model for the atmosphere of hot Jupiters (2012, background): “This choice is motivated by the comparison with M11 and also because the actual physical structure of these atmospheres is not yet well constrained by observations; however, Huitson et al. (2012) have recently published thermal profiles for both planets, as inferred from transit spectroscopy.”
Hubble Space Telescope hot Jupiter transmission spectral survey: a detection of Na and strong optical absorption in HAT-P-1b (2013, methodology): “Previous STIS data analyses showed that the first integration exhibits abnormally low flux (Charbonneau et al. 2002; Sing et al. 2008b; Pont et al. 2008; Sing et al. 2011a; Huitson et al. 2012).”
HST hot-Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b (2013, methodology): “This observing technique has proven to produce high signal-to-noise (S/N) spectra which are photometrically accurate near the Poisson limit during a transit event (e.g Brown 2001; Sing et al. 2011; Huitson et al. 2012).”
Detection of carbon monoxide in the high-resolution day-side spectrum of the exoplanet HD 189733b (2013, background): “An optically thick haze layer would also require a cold atmospheric layer above the haze layer, which is contrary to the conclusions of Huitson et al. (2012).”
A CONSISTENT RETRIEVAL ANALYSIS OF 10 HOT JUPITERS OBSERVED IN TRANSMISSION (2016, background): “We note that while we have assumed a uniform temperature for the retrieval, detailed analysis of the sodium line has revealed a hot thermosphere at the upper atmospheric layers for this planet ((Huitson et al. 2012; Wyttenbach et al. 2015).”
The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations (2012, methodology): “We therefore fit the amplitude of a potassium line model to the pixel-by-pixel data, with the model used in Huitson et al. (2012) to fit the potassium line and surrounding Rayleigh scattering slope, which is based upon the analytic expression from Lecavelier Des Etangs et al. (2008).”