Observations of Exoplanet Atmospheres

Crossfield, Ian J. M.

doi:10.1086/683115

Cited by 133 publications

(93 citation statements)

References 266 publications

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“…The power law causes two planets to scatter to greater A H values at the left edge of Figure 2, degrading the correlation, but not affecting the baseline derived in the bottom panel of Figure 2. A similar temperature versus A H correlation was reported by Crossfield & Kreidberg (2017) with a sample size comprised of six Neptune-size planets. The correlation led them to suggest that hazes might become more significant for planets with < T 850 K eq .…”

Section: Statistical Correlationssupporting

confidence: 81%

“…Robust observations of exoplanetary atmospheres using transmission and emission spectroscopy with the Wide Field Camera-3 (WFC3) on the Hubble Space Telescope (HST) have led to significant progress in understanding exoplanetary atmospheres (see reviews by Crossfield 2015 andSeager 2017). Recent intriguing results have inferred atmospheric thermal structure and circulation patterns (Stevenson et al 2014), temperature inversions (Haynes et al 2015;Evans et al 2017), clouds/hazes , and water abundance (Kreidberg et al 2014a;Wakeford et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets

Deming

Knutson

et al. 2017

ApJL

115

108

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Transmission spectroscopy provides a window to study exoplanetary atmospheres, but that window is fogged by clouds and hazes. Clouds and haze introduce a degeneracy between the strength of gaseous absorption features and planetary physical parameters such as abundances. One way to break that degeneracy is via statistical studies. We collect all published HST/WFC3 transit spectra for 1.1-1.65 μm water vapor absorption and perform a statistical study on potential correlations between the water absorption feature and planetary parameters. We fit the observed spectra with a template calculated for each planet using the Exo-transmit code. We express the magnitude of the water absorption in scale heights, thereby removing the known dependence on temperature, surface gravity, and mean molecular weight. We find that the absorption in scale heights has a positive baseline correlation with planetary equilibrium temperature; our hypothesis is that decreasing cloud condensation with increasing temperature is responsible for this baseline slope. However, the observed sample is also intrinsically degenerate in the sense that equilibrium temperature correlates with planetary mass. We compile the distribution of absorption in scale heights, and we find that this distribution is closer to log-normal than Gaussian. However, we also find that the distribution of equilibrium temperatures for the observed planets is similarly log-normal. This indicates that the absorption values are affected by observational bias, whereby observers have not yet targeted a sufficient sample of the hottest planets.

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Section: Statistical Correlationssupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets

Deming

Knutson

et al. 2017

ApJL

115

108

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“…7 In just two decades, exoplanets have transitioned from mere theoretical possibility to highly characterizable systems. There are now radius measurements of Earth-like planets, aided by asteroseismology, with error bars precise to 120 km (Ballard et al 2014); there is evidence that clouds pervade the atmospheres of exoplanets across the mass spectrum from super-Earths to hot Jupiters (e.g., Evans et al 2013;Kreidberg et al 2014;Heng 2016;Sing et al 2016); there are a growing number of robust detections of elemental and molecular species in transiting planets using the Hubble Space Telescope, including sodium, potassium, and water (see e.g., Crossfield 2015 for an up-to-date review of chemicals observed in exoplanet atmospheres), alongside the first detections of carbon monoxide, water, and methane in the atmospheres of widely separated directly imaged giants planets (e.g., Konopacky et al 2013;Snellen et al 2014;Barman et al 2015;Macintosh et al 2015), and in the atmospheres of non-transiting hot Jupiters using ground-based high-resolution spectroscopy (Brogi et al 2012;Rodler et al 2012;Lockwood et al 2014). Even the global wind dynamics and atmospheric circulation of hot Jupiters have been studied in detail (e.g., Knutson et al 2009;Stevenson et al 2014;Louden & Wheatley 2015;Brogi et al 2016a;Zhou et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Discovery of Water at High Spectral Resolution in the Atmosphere of 51 Peg b

Birkby¹,

Kok²,

Brogi³

et al. 2017

184

244

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We report the detection of water absorption features in the day side spectrum of the first-known hot Jupiter, 51 Peg b, confirming the star-planet system to be a double-lined spectroscopic binary. We use high-resolution ( » R 100,000), m 3.2 m spectra taken with CRIRES/VLT to trace the radial-velocity shift of the water features in the planet's day side atmosphere during 4 hr of its 4.23 day orbit after superior conjunction. We detect the signature of molecular absorption by water at a significance of J , placing it at the transition boundary between Jovian and Neptunian worlds. We determine upper and lower limits on the orbital inclination of the system of  < <  i 70 8 2.2. We also provide an updated orbital solution for 51 Peg b, using an extensive set of 639 stellar radial velocities measured between 1994 and 2013, finding no significant evidence of an eccentric orbit. We find no evidence of significant absorption or emission from other major carbon-bearing molecules of the planet, including methane and carbon dioxide. The atmosphere is non-inverted in the temperature-pressure region probed by these observations. The deepest absorption lines reach an observed relative contrast of´-0.9 10 3 with respect to the host star continuum flux at an angular separation of 3 milliarcseconds. This work is consistent with a previous tentative report of K-band molecular absorption for 51 Peg b by Brogi et al.

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“…However, subsequent observations have revealed no clear evidence for temperature inversions in hot Jupiters with daysides cooler than 2500 K (e.g., Madhusudhan et al 2014;Crossfield 2015). The lack of inversions in hot Jupiters led to suggestions that UV radiation from the host stars may be photodisassociating TiO/VO (Knutson et al 2010), or that TiO/VO may be condensing and settling out of the atmosphere on the dayside (Spiegel et al 2009) or the nightside (Parmentier et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Evidence for Atmospheric Cold-trap Processes in the Noninverted Emission Spectrum of Kepler-13Ab Using HST/WFC3

Beatty

Madhusudhan

Tsiaras

et al. 2017

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We observed two eclipses of the Kepler-13A planetary system, on UT 2014 April 28 and UT 2014 October 13, in the near-infrared using Wide Field Camera 3 on the Hubble Space Telescope. By using the nearby binary stars Kepler-13BC as a reference, we were able to create a differential light curve for Kepler-13A that had little of the systematics typically present in HST/WFC3 spectrophotometry. We measure a broadband (1.1-1.65 μm) eclipse depth of 734±28 ppm and are able to measure the emission spectrum of the planet at R≈50 with an average precision of 70 ppm. We find that Kepler-13Ab possesses a noninverted, monotonically decreasing vertical temperature profile. We exclude an isothermal profile and an inverted profile at more than 3σ. We also find that the dayside emission of Kepler-13Ab appears generally similar to an isolated M7 brown dwarf at a similar effective temperature. Due to the relatively high mass and surface gravity of Kepler-13Ab, we suggest that the apparent lack of an inversion is due to cold-trap processes in the planet's atmosphere. Using a toy model for where cold traps should inhibit inversions, as well as observations of other planets in this temperature range with measured emission spectra, we argue that with more detailed modeling and more observations we may be able to place useful constraints on the size of condensates on the daysides of hot Jupiters.

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Observations of Exoplanet Atmospheres

Cited by 133 publications

References 266 publications

Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets

Statistical Analysis of Hubble/WFC3 Transit Spectroscopy of Extrasolar Planets

Discovery of Water at High Spectral Resolution in the Atmosphere of 51 Peg b

Evidence for Atmospheric Cold-trap Processes in the Noninverted Emission Spectrum of Kepler-13Ab Using HST/WFC3

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