Detection of sodium absorption in WASP-17b with Magellan

Zhou, G.; Bayliss, Daniel

doi:10.1111/j.1365-2966.2012.21817.x

Cited by 42 publications

(44 citation statements)

References 34 publications

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“…In addition to the contaminating water lines around the Na  doublet, we expect the observed spectra to also possess a signature of the telluric sodium (Vidal-Madjar et al 2010). Even if the telluric sodium undergoes seasonal variations and possibly does not follow the water absorption levels, we assume that within a night, this telluric sodium absorption behaves and can be corrected for as other telluric features (Snellen et al 2008;Zhou & Bayliss 2012). Furthermore, visual inspection of our telluric spectra did not reveal any obvious telluric sodium features.…”

Section: Telluric Correctionmentioning

confidence: 79%

Spectrally resolved detection of sodium in the atmosphere of HD 189733b with the HARPS spectrograph

Wyttenbach

Ehrenreich

Lovis

et al. 2015

A&A

306

487

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Context. Atmospheric properties of exoplanets can be constrained with transit spectroscopy. At low spectral resolution, this technique is limited by the presence of clouds. The signature of atomic sodium (Na ), known to be present above the clouds, is a powerful probe of the upper atmosphere, where it can be best detected and characterized at high spectral resolution. Aims. Our goal is to obtain a high-resolution transit spectrum of HD 189733b in the region around the resonance doublet of Na  at 589 nm, to characterize the absorption signature that was previously detected from space at low resolution.Methods. We analyzed archival transit data of HD 189733b obtained with the HARPS spectrograph (R = 115 000) at the ESO 3.6-m telescope. We performed differential spectroscopy to retrieve the transit spectrum and light curve of the planet, implementing corrections for telluric contamination and planetary orbital motion. We compared our results to synthetic transit spectra calculated from isothermal models of the planetary atmosphere.Results. We spectrally resolve the Na  D doublet and measure line contrasts of 0.64 ± 0.07% (D2) and 0.40 ± 0.07% (D1) and FWHMs of 0.52 ± 0.08 Å. This corresponds to a detection at the 10σ level of excess of absorption of 0.32 ± 0.03% in a passband of 2 × 0.75 Å centered on each line. We derive temperatures of 2600 ± 600 K and 3270 ± 330 K at altitudes of 9800 ± 2800 and 12 700 ± 2600 km in the Na  D1 and D2 line cores, respectively. We measure a temperature gradient of ∼0.2 K km −1 in the region where the sodium absorption dominates the haze absorption from a comparison with theoretical models. We also detect a blueshift of 0.16 ± 0.04 Å (4σ) in the line positions. This blueshift may be the result of winds blowing at 8 ± 2 km s −1 in the upper layers of the atmosphere. Conclusions. We demonstrate the relevance of studying exoplanet atmospheres with high-resolution spectrographs mounted on 4-m-class telescopes. Our results pave the way for an in-depth characterization of physical conditions in the atmospheres of many exoplanetary systems with future spectrographs such as ESPRESSO on the VLT or HiReS and METIS on the E-ELT.

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Section: Telluric Correctionmentioning

confidence: 79%

Spectrally resolved detection of sodium in the atmosphere of HD 189733b with the HARPS spectrograph

Wyttenbach

Ehrenreich

Lovis

et al. 2015

A&A

306

487

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“…Detections have been reported of Na I (Charbonneau et al 2002;Redfield et al 2008;Sing et al 2008Sing et al , 2012Sing et al , 2016Jensen et al 2011;Huitson et al 2012;Zhou & Bayliss 2012;Nikolov et al 2014), K I (Sing et al 2011, and H 2 O (Stevenson et al 2016) in the atmospheres of hot Jupiters. Evans et al (2016) have presented evidence for TiO/VO in WASP-121b, while non-detections of TiO/VO in other hot, giant exoplanets (Huitson et al 2013;Sing et al 2013) could point to breakdown by stellar activity (Knutson et al 2010) or the presence of a high-altitude opacity source, either due to lofted cloud decks or photochemical hazes (Seager & Sasselov 2000;Fortney 2005;Howe & Burrows 2012;Morley et al 2013Morley et al , 2015.…”

Section: Introductionmentioning

confidence: 99%

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Rackham

Espinoza

Apai

et al. 2017

ApJ

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GJ1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanetʼs atmosphere, either equilibrium condensate clouds or photochemical hazes. Many photometric observations have been reported in the optical by different groups, though simultaneous measurements spanning the entire optical regime are lacking. We present an optical transmission spectrum (4500-9260Å) of GJ1214b in 14 bins, measured with Magellan/IMACS repeatedly over three transits. We measure a mean planet-to-star radius ratio of ( ) in the spectral bins. The optical transit depths are shallower on average than observed in the near-infrared. We present a model for jointly incorporating the effects of a composite photosphere and atmospheric transmission through the exoplanetʼs limb (the CPAT model), and use it to examine the cases of absorber and temperature heterogeneities in the stellar photosphere. We find the optical and near-infrared measurements are best explained by the combination of (1) photochemical haze in the exoplanetary atmosphere with a mode particle size r=0.1μm and haze-forming efficiency = f 10% haze and (2) faculae in the unocculted stellar disk with a temperature contrast D = -+ T 354 46 46 K, assuming 3.2% surface coverage. The CPAT model can be used to assess potential contributions of heterogeneous stellar photospheres to observations of exoplanet transmission spectra, which will be important for searches for spectral features in the optical.

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“…The Na i line cores, in particular, can trace the temperature profile up to the planet thermosphere, which has been measured effectively with the HARPS spectrograph on HD 189733b Heng et al 2015). Sodium is arguably the easiest species to detect in a hot exoplanet atmosphere, and ground-based detections have been achieved for several gas giants (Redfield et al 2008;Snellen et al 2008;Wood et al 2011;Jensen et al 2011;Zhou & Bayliss 2012;Murgas et al 2014;Burton et al 2015;Khalafinejad et al 2016;Nikolov et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

Wyttenbach

Lovis

Ehrenreich

et al. 2017

A&A

117

151

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High-resolution optical spectroscopy during the transit of HD 189733b, a prototypical hot Jupiter, allowed the resolution of the Na i D sodium lines in the planet, giving access to the extreme conditions of the planet upper atmosphere. We have undertaken HEARTS, a spectroscopic survey of exoplanet upper atmospheres, to perform a comparative study of hot gas giants and determine how stellar irradiation affect them. Here, we report on the first HEARTS observations of the hot Saturn-mass planet WASP-49b. We observed the planet with the HARPS high-resolution spectrograph at ESO 3.6m telescope. We collected 126 spectra of WASP-49, covering three transits of WASP-49b. We analyzed and modeled the planet transit spectrum, while paying particular attention to the treatment of potentially spurious signals of stellar origin. We spectrally resolve the Na i D lines in the planet atmosphere and show that these signatures are unlikely to arise from stellar contamination. The large contrasts of 2.0 ± 0.5% (D 2 ) and 1.8 ± 0.7% (D 1 ) require the presence of hot neutral sodium (2, 950 +400 −500 K) at high altitudes (∼1.5 planet radius or ∼45,000 km). From estimating the cloudiness index of WASP-49b, we determine its atmosphere to be cloud free at the altitudes probed by the sodium lines. WASP-49b is close to the border of the evaporation desert and exhibits an enhanced thermospheric signature with respect to a farther-away planet such as HD 189733b.

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Detection of sodium absorption in WASP-17b with Magellan

Cited by 42 publications

References 34 publications

Spectrally resolved detection of sodium in the atmosphere of HD 189733b with the HARPS spectrograph

Spectrally resolved detection of sodium in the atmosphere of HD 189733b with the HARPS spectrograph

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

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