Transit spectroscopy with James Webb Space Telescope: systematics, starspots and stitching

Barstow, Joanna K.; Aigrain, S.; Irwin, Patrick; Kendrew, Sarah; Fletcher, Leigh N.

doi:10.1093/mnras/stv186

Cited by 129 publications

(114 citation statements)

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“…Nonetheless, the modeling efforts of the telescope performance in conjunction with models of exoplanet atmospheres have already been started and include Deming et al (2009), Batalha et al (2015), Mordasini et al (2016). Studies which additionally look into the question of retrievability of the atmospheric properties as a function of the planet-star parameters can be found Barstow et al (2015), Greene et al (2016), Barstow & Irwin (2016). Barstow et al (2015) also included time-dependent astrophysical noise (starspots) for stitched observations.…”

Section: While the Question Of The Origins Of Clouds Is Fundamentalmentioning

confidence: 99%

“…Studies which additionally look into the question of retrievability of the atmospheric properties as a function of the planet-star parameters can be found Barstow et al (2015), Greene et al (2016), Barstow & Irwin (2016). Barstow et al (2015) also included time-dependent astrophysical noise (starspots) for stitched observations.…”

Section: While the Question Of The Origins Of Clouds Is Fundamentalmentioning

confidence: 99%

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Observing transiting planets with JWST

Mollière

Boekel

Bouwman

et al. 2017

A&A

185

250

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Context. The James Webb Space Telescope will enable astronomers to obtain exoplanet spectra of unprecedented precision. The MIRI instrument especially may shed light on the nature of the cloud particles obscuring planetary transmission spectra in the optical and near-infrared. Aims. We provide self-consistent atmospheric models and synthetic JWST observations for prime exoplanet targets in order to identify spectral regions of interest and estimate the number of transits needed to distinguish between model setups. Methods. We select targets that span a wide range of planetary temperatures and surface gravities, ranging from super-Earths to giant planets, that have a high expected signal-to-noise ratio. For all targets, we vary the enrichment, C/O ratio, presence of optical absorbers (TiO/VO), and cloud treatment. We calculate atmospheric structures, emission, and transmission spectra for all targets and use a radiometric model to obtain simulated observations. Further, we analyze JWST's ability to distinguish between various scenarios. Results. We find that in very cloudy planets, such as GJ 1214b, less than ten transits with NIRSpec may be enough to reveal molecular features. Furthermore, the presence of small silicate grains in atmospheres of hot Jupiters may be detectable with a single JWST MIRI transit. For a more detailed characterization of such particles less than ten transits are necessary. Finally, we find that some of the hottest hot Jupiters are well fitted by models which neglect the redistribution of the insolation and harbor inversions, and that 1-4 eclipse measurements with NIRSpec are needed to distinguish between the inversion models.Conclusions. Wet thus demonstrate the capabilities of JWST for solving some of the most intriguing puzzles in current exoplanet atmospheric research. Further, by publishing all models calculated for this study we enable the community to carry out similar studies, as well as retrieval analyses for all planets included in our target list.

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Section: While the Question Of The Origins Of Clouds Is Fundamentalmentioning

confidence: 99%

Section: While the Question Of The Origins Of Clouds Is Fundamentalmentioning

confidence: 99%

Observing transiting planets with JWST

Mollière

Boekel

Bouwman

et al. 2017

A&A

185

250

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“…Stellar variability, in the form of starspots and faculae, can affect the measured transit depth of an exoplanet and hence its spectrum and retrieved physical properties (Pont et al 2008;Silva-Valio 2008;Czesla et al 2009;Wolter et al 2009;Agol et al 2010;Berta et al 2011;Carter et al 2011;Désert et al 2011;Sing et al 2011;Fraine et al 2014;McCullough et al 2014;Oshagh et al 2014;Barstow et al 2015;Damasso et al 2015;Zellem et al 2015;Rackham et al 2017). As a worst-case scenario for very active stars, unocculted spots can cause an underestimation of the planet-to-star radius ratio of up to 4% at near-infrared wavelengths and up to 10% at visible wavelengths, while faculae can cause an overestimation of the planet-to-star radius ratio of up to ∼0.2% at near-infrared wavelengths and up to ∼3% at visible wavelengths (Oshagh et al 2014).…”

Section: Introductionmentioning

confidence: 99%

“…Unocculted spots can also mimic a Rayleigh scattering slope indicative of haze; for example, the visible and near-IR slope of the exoplanet HD 189733b's transit absorption spectrum, interpreted as Rayleigh scattering by haze particles (Pont et al 2008(Pont et al , 2013Sing et al 2011Sing et al , 2016, has also been interpreted as unocculted starspots on its active K0 host star (McCullough et al 2014). Unocculted spots can also introduce false molecular spectral modulation into an exoplanet's spectrum, such as H 2 O if the spots are sufficiently cool (Fraine et al 2014;Barstow et al 2015). Stellar faculae, which are brighter than the stellar photosphere, decrease the transit depth at optical wavelengths (Rackham et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Forecasting the Impact of Stellar Activity on Transiting Exoplanet Spectra

Zellem

Swain

Roudier

et al. 2017

ApJ

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Exoplanet host star activity, in the form of unocculted starspots or faculae, alters the observed transmission and emission spectra of the exoplanet. This effect can be exacerbated when combining data from different epochs if the stellar photosphere varies between observations due to activity. Here, we present a method to characterize and correct for relative changes due to stellar activity by exploiting multi-epoch (2 visits/transits) observations to place them in a consistent reference frame. Using measurements from portions of the planet's orbit where negligible planet transmission or emission can be assumed, we determine changes to the stellar spectral amplitude. With the analytical methods described here, we predict the impact of stellar variability on transit observations. Supplementing these forecasts with Kepler-measured stellar variabilities for F-, G-, K-, and M-dwarfs, and predicted transit precisions by the James Webb Space Telescope's (JWST) NIRISS, NIRCam, and MIRI, we conclude that stellar activity does not impact infrared transiting exoplanet observations of most presently known or predicted TESS targets by current or near-future platforms, such as JWST, as activity-induced spectral changes are below the measurement precision.

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“…Several studies have recently simulated JW ST spectra of a variety of planet types and have assessed what can be learned from these data from direct examination of spectra (Deming et al 2009;Mollière et al 2017) or statistical Bayesian retrieval techniques (Barstow et al 2015;Greene et al 2016;Rocchetto et al 2016;Batalha and Line 2017;Howe et al 2017). We now draw from these works to discuss the expected data quality and molecular features that may be detectable in JW ST spectra of several different types of exoplanet atmospheres.…”

Section: Observations Of Archetypal Transiting Systemsmentioning

confidence: 98%

Observing Exoplanets with the James Webb Space Telescope

Beichman

Greene

2017

Handbook of Exoplanets

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The census of exoplanets has revealed an enormous variety of planets orbiting stars of all ages and spectral types: planets in orbits of less than a day to frigid worlds in orbits over 100 AU; planets with masses 10 times that of Jupiter to planets with masses less than that of Earth; searingly hot planets to temperate planets in the Habitable Zone. The challenge of the coming decade is to move from demography to physical characterization. The James Webb Space Telescope (JWST) is poised to open a revolutionary new phase in our understanding of exoplanets with transit spectroscopy of relatively short period planets and coronagraphic imaging of ones with wide separations from their host stars. This article discusses the wide variety of exoplanet opportunities enabled by JWST's sensitivity and stability, its high angular resolution, and its suite of powerful instruments. These capabilities will advance our understanding of planet formation, brown dwarfs, and the atmospheres of young to mature planets.

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Transit spectroscopy with James Webb Space Telescope: systematics, starspots and stitching

Cited by 129 publications

References 50 publications

Observing transiting planets with JWST

Observing transiting planets with JWST

Forecasting the Impact of Stellar Activity on Transiting Exoplanet Spectra

Observing Exoplanets with the James Webb Space Telescope

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