CHARACTERIZING TRANSITING EXOPLANET ATMOSPHERES WITH JWST

By T. Greene, M. Line, C. Montero, Jon Fortney, J. Lustig-Yaeger, Kyle L. Luther. 2015

263 citations recorded by the source corpus.

We explore how well spectra from the James Webb Space Telescope (JWST) will likely constrain bulk atmospheric properties of transiting exoplanets. We start by modeling the atmospheres of archetypal hot Jupiter, warm Neptune, warm sub-Neptune, and cool super-Earth planets with atmospheres that are clear, cloudy, or of high mean molecular weight (HMMW). Next we simulate the λ = 1–11 μm transmission and emission spectra of these systems for several JWST instrument modes for single-transit or single-eclipse events. We then perform retrievals to determine how well temperatures and molecular mixing ratios (CH4, CO, CO2, H2O, NH3) can be constrained. We find that λ = 1–2.5 μm transmission spectra will often constrain the major molecular constituents of clear solar-composition atmospheres well. Cloudy or HMMW atmospheres will often require full 1–11 μm spectra for good constraints, and emission data may be more useful in cases of sufficiently high Fp and high Fp/F*. Strong temperature inversions in the solar-composition hot-Jupiter atmosphere should be detectable with 1–2.5+ μm emission spectra, and 1–5+ μm emission spectra will constrain the temperature–pressure profiles of warm planets. Transmission spectra over 1–5+ μm will constrain [Fe/H] values to better than 0.5 dex for the clear atmospheres of the hot and warm planets studied. Carbon-to-oxygen ratios can be constrained to better than a factor of 2 in some systems. We expect that these results will provide useful predictions of the scientific value of single-event JWST spectra until its on-orbit performance is known.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b2902eab3f9e65a4e4e60c8c6ed716f430822772

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Citations in the corpus

Pale Orange Dots: The Impact of Organic Haze on the Habitability and Detectability of Earthlike Exoplanets (2016, background): “However, if the JWST systematic noise represents a floor at the > 10 ppm level, as proposed by Greene et al. (2016), then characterizing the hazy exoEarths presented here becomes extremely difficult, and the error bars on our simulated JWST measurements will become much larger.”
The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint (2017, background): “Given that significant O and C could be locked up in other species such as condensates (Greene et al. 2016), the inclusion of optical data may also prove useful to identify potential biases when estimating the C/O ratio solely from the major molecular components.”
The Detectability and Characterization of the TRAPPIST-1 Exoplanet Atmospheres with JWST (2019, methodology): “…atmospheres (e.g., Belu et al. 2011), we agree with previous works that transmission spectroscopy is more viable (e.g., Hedelt et al. 2013; Barstow & Irwin 2016; Barstow et al. 2016; Greene et al. 2016), particularly for temperate and cool planets that emit considerably less thermal flux.”
Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST (2017, background): “While atmospheres of Neptune-sized and giant planets will be detectable around sunlike stars with the upcoming James Webb Space Telescope (JWST) (e.g., Greene et al. 2016), the atmospheres of planets around the size of Earth will not be.”
Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs (2017, background): “Assuming that JWST encounters no systematic noise floor (which is unlikely), we can calculate how many observing hours would be needed to obtain sub-10 ppm precision.”
An Accurate, Extensive, and Practical Line List of Methane for the HITEMP Database (2020, unknown): “3500) spectroscopy (Greene et al. 2016).”
The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets (2017, methodology): “This is similar to the noise floors for James Webb Space Telescope (JWST ) instruments adopted by Greene et al. (2016) for wavelength ranges of interest in this study: 20 ppm for NIRISS SOSS (λ = 1–2.5 µm) and 30 ppm for NIRCam grism (λ = 2.5–5.0 µm).”
Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects (2019, background): “While various surveys from space and ground are expected to detect numerous more exoplanets orbiting nearby stars, the imminent launch of JWST along with large groundbased facilities are expected to revolutionise exoplanetary spectroscopy.”