A ground-based transmission spectrum of the super-Earth exoplanet GJ 1214b

Bean, Jacob L.; Kempton, Eliza M.-R.; Homeier, D.

doi:10.1038/nature09596

Cited by 374 publications

(459 citation statements)

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“…This framework is empirically motivated, as the data show that simply dividing the target light curve by the sum of the comparison light curves removes most of the variations in the out-of-transit flux from the target, leaving only a smoothly varying long-term trend. Like Bean et al (2010), we find that this trend can be modeled well as a second order polynomial function of time, and attribute it to the color difference between this very red target star and the available comparison stars in the field. In this framework, the target light curve can be expressed as…”

Section: Polynomial-based Modeling Frameworkmentioning

confidence: 99%

“…Starting with the first results provided by Bean et al (2010), observations of GJ1214b in the optical and near-infrared have found a featureless spectrum Crossfield et al 2011;Désert et al 2011;Berta et al 2012;Murgas et al 2012;Colón & Gaidos 2013;de Mooij et al 2013;Fraine et al 2013;Teske et al 2013;Cáceres et al 2014;Gillon et al 2014;Wilson et al 2014;Nascimbeni et al 2015). Reported spectral features in the near-infrared (Croll et al 2011;de Mooij et al 2012) have not been reproduced by follow-up measurements in the same bandpasses (Narita et al 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Since its discovery, many groups have published measurements of GJ1214bʼs transmission spectrum in the optical and nearinfrared (Bean et al 2010Croll et al 2011;Crossfield et al 2011;Désert et al 2011;Berta et al 2012;de Mooij et al 2012de Mooij et al , 2013Murgas et al 2012;Colón & Gaidos 2013;Fraine et al 2013;Narita et al 2013;Teske et al 2013;Cáceres et al 2014;Gillon et al 2014;Kreidberg et al 2014;Wilson et al 2014;Nascimbeni et al 2015). A total of 58 measurements have been published for bandpasses with central wavelengths shorter than 9260Å, the longest wavelength in our Magellan/ IMACS spectrum.…”

Section: Previous Measurementsmentioning

confidence: 99%

“…We also modeled the observed target light curve following the procedure employed by Bean et al (2010) in their successful VLT/FORS observations of GJ1214b. This framework is empirically motivated, as the data show that simply dividing the target light curve by the sum of the comparison light curves removes most of the variations in the out-of-transit flux from the target, leaving only a smoothly varying long-term trend.…”

Section: Polynomial-based Modeling Frameworkmentioning

confidence: 99%

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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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Section: Polynomial-based Modeling Frameworkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Previous Measurementsmentioning

confidence: 99%

Section: Polynomial-based Modeling Frameworkmentioning

confidence: 99%

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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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“…This technique was pioneered by Bean, Miller-Ricci Kempton & Homeier (2010), using the VLT to produce a transmission spectrum of the super-Earth GJ 1214b. Such observations have benefited not only from advances in observing strategy, but also from the availability of new bright targets with nearby comparison stars.…”

Section: Introductionmentioning

confidence: 99%

A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720 nm

Gibson¹,

Aigrain²,

Barstow³

et al. 2012

Monthly Notices of the Royal Astronomical Society

137

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We report Gemini-South GMOS observations of the exoplanet system WASP-29 during primary transit as a test case for differential spectrophotometry. We use the multi-object spectrograph to observe the target star and a comparison star simultaneously to produce multiple light curves at varying wavelengths. The 'white' light curve and fifteen 'spectral' light curves are analysed to refine the system parameters and produce a transmission spectrum from ∼515 to 720 nm. All light curves exhibit time-correlated noise, which we model using a variety of techniques. These include a simple noise rescaling, a Gaussian process model, and a wavelet based method. These methods all produce consistent results, although with different uncertainties. The precision of the transmission spectrum is improved by subtracting a common signal from all the spectral light curves, reaching a typical precision of ∼1×10 −4 in transit depth. The transmission spectrum is free of spectral features, and given the non-detection of a pressure broadened Na feature, we can rule out the presence of a Na rich atmosphere free of clouds or hazes, although we cannot rule out a narrow Na core. This indicates that Na is not present in the atmosphere, and/or that clouds/hazes play a significant role in the atmosphere and mask the broad wings of the Na feature, although the former is a more likely explanation given WASP-29b's equilibrium temperature of ∼970 K, at which Na can form various compounds. We also briefly discuss the use of Gaussian process and wavelet methods to account for time correlated noise in transit light curves.

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Illusion and reality in the atmospheres of exoplanets

2017

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The atmospheres of exoplanets reveal all their properties beyond mass, radius, and orbit. Based on bulk densities, we know that exoplanets larger than 1.5 Earth radii must have gaseous envelopes and, hence, atmospheres. We discuss contemporary techniques for characterization of exoplanetary atmospheres. The measurements are difficult, because—even in current favorable cases—the signals can be as small as 0.001% of the host star's flux. Consequently, some early results have been illusory and not confirmed by subsequent investigations. Prominent illusions to date include polarized scattered light, temperature inversions, and the existence of carbon planets. The field moves from the first tentative and often incorrect conclusions, converging to the reality of exoplanetary atmospheres. That reality is revealed using transits for close‐in exoplanets and direct imaging for young or massive exoplanets in distant orbits. Several atomic and molecular constituents have now been robustly detected in exoplanets as small as Neptune. In our current observations, the effects of clouds and haze appear ubiquitous. Topics at the current frontier include the measurement of heavy element abundances in giant planets, detection of carbon‐based molecules, measurement of atmospheric temperature profiles, definition of heat circulation efficiencies for tidally locked planets, and the push to detect and characterize the atmospheres of super‐Earths. Future observatories for this quest include the James Webb Space Telescope and the new generation of extremely large telescopes on the ground. On a more distant horizon, NASA's study concepts for the Habitable Exoplanet Imaging Mission (HabEx) and the Large UV/Optical/Infrared Surveyor (LUVOIR) missions could extend the study of exoplanetary atmospheres to true twins of Earth.

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A ground-based transmission spectrum of the super-Earth exoplanet GJ 1214b

Cited by 374 publications

References 22 publications

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

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

A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720 nm

Illusion and reality in the atmospheres of exoplanets

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