Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b

Edwards, Billy; Changeat, Quentin; Mori, M.; Anisman, Lara; Morvan, Mario; Yip, Kai Hou; Tsiaras, Angelos; Al-Refaie, Ahmed; Waldmann, I. P.; Tinetti, Giovanna

doi:10.3847/1538-3881/abc6a5

Cited by 83 publications

(63 citation statements)

References 84 publications

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“…For TRAPPIST-1, the combined spectrum of planets b-g shows an inverted water absorption signature that is consistent with H2O features in stellar faculae. The transmission spectrum of LHS 1140 b also has a marginally significant (2.65σ), noninverted water feature, but this too is consistent with expectations for stellar contamination (Edwards et al 2021). For planets around the coolest stars, H2O contamination from an imhomogeneous photosphere may be the norm and should be taken into account in the analysis of the spectra (Iyer & Line 2020).…”

Section: Planets With M-dwarf Host Starssupporting

confidence: 73%

Atmospheres of Rocky Exoplanets

Wordsworth,

Kreidberg

2021

Preprint

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Rocky planets are common around other stars, but their atmospheric properties remain largely unconstrained. Thanks to a wealth of recent planet discoveries and upcoming advances in observing capability, we are poised to characterize the atmospheres of dozens of rocky exoplanets in this decade. Theoretical understanding of rocky exoplanet atmospheres has advanced considerably in the last few years, yielding testable predictions of their evolution, chemistry, dynamics and even possible biosignatures. Here we review key progress in this field to date and discuss future objectives. Our major conclusions are:• Many rocky planets may form with initial H2 -He envelopes that are later lost to space, likely due to a combination of stellar UV/Xray irradiation and internal heating. • After the early stages of evolution, a wide diversity of atmospheric compositions is expected, due to variations in host star flux, atmospheric escape rates, interior exchange and other factors. • Observations have ruled out the presence of hydrogen-dominated atmospheres on several nearby rocky exoplanets, and the presence of any thick atmosphere on one target. More detailed atmospheric characterization of these planets and others will become possible in the near future. • Exoplanet biosphere searches are an exciting future goal. However, reliable detections for a representative sample of planets will require further advances in observing capability and improvements in our understanding of abiotic planetary processes.

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Section: Planets With M-dwarf Host Starssupporting

confidence: 73%

Atmospheres of Rocky Exoplanets

Wordsworth,

Kreidberg

2021

Preprint

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“…Theoretical studies and observational works based on data from HST have explored the atmospheric compositions for gas dwarf atmospheres (e.g., Elkins-Tanton & Seager 2008;Miller-Ricci et al 2008;Seager & Deming 2010;Benneke & Seager 2012). Recently, HST observations showed that water vapor was present in the atmosphere, which indicates a thick hydrogen-rich gas envelope for K2-18 b (Benneke et al 2019b;Madhusudhan et al 2020), and evidence of a thick atmosphere for LHS 1140 b (Edwards et al 2021).…”

Section: Varying Atmospheric Compositionmentioning

confidence: 99%

Detecting Biosignatures in the Atmospheres of Gas Dwarf Planets with the James Webb Space Telescope

Phillips

Kendrew

et al. 2021

ApJ

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Exoplanets with radii between those of Earth and Neptune have stronger surface gravity than Earth, and can retain a sizable hydrogen-dominated atmosphere. In contrast to gas giant planets, we call these planets gas dwarf planets. The James Webb Space Telescope (JWST) will offer unprecedented insight into these planets. Here, we investigate the detectability of ammonia (NH3, a potential biosignature) in the atmospheres of seven temperate gas dwarf planets using various JWST instruments. We use petitRadTRANS and PandExo to model planet atmospheres and simulate JWST observations under different scenarios by varying cloud conditions, mean molecular weights (MMWs), and NH3 mixing ratios. A metric is defined to quantify detection significance and provide a ranked list for JWST observations in search of biosignatures in gas dwarf planets. It is very challenging to search for the 10.3–10.8 μm NH3 feature using eclipse spectroscopy with the Mid-Infrared Instrument (MIRI) in the presence of photon and a systemic noise floor of 12.6 ppm for 10 eclipses. NIRISS, NIRSpec, and MIRI are feasible for transmission spectroscopy to detect NH3 features from 1.5–6.1 μm under optimal conditions such as a clear atmosphere and low MMWs for a number of gas dwarf planets. We provide examples of retrieval analyses to further support the detection metric that we use. Our study shows that searching for potential biosignatures such as NH3 is feasible with a reasonable investment of JWST time for gas dwarf planets given optimal atmospheric conditions.

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“…An emerging trend in the haziness of cooler planets (see Crossfield & Kreidberg 2017;Libby-Roberts et al 2020;Yu et al 2021;Dymont et al 2021) hints that planets with T eq < 300 K may have clear atmospheres, as possibly shown by K2-18 b (T eq =282 K; Benneke et al 2019;Tsiaras et al 2019) and LHS 1140 b (T eq =229 K; Edwards et al 2021). Following Dymont et al (2021), we compute the 1.4 µm H 2 O feature amplitude (A H ) and add HIP 41378 f to the sample of cooler (T eq < 1000 K) planets with measured WFC3 transmission spectra (Figure 3).…”

Section: Placing Hip 41378 F In Contextmentioning

confidence: 99%

The First Near-Infrared Transmission Spectrum of HIP 41378 f, a Low-Mass Temperate Jovian World in a Multi-Planet System

Alam,

Kirk,

Dressing

et al. 2022

Preprint

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We present a near-infrared transmission spectrum of the long period (P=542 days), temperate (T eq =294 K) giant planet HIP 41378 f obtained with the Wide-Field Camera 3 (WFC3) instrument aboard the Hubble Space Telescope (HST). With a measured mass of 12 ± 3 M ⊕ and a radius of 9.2 ± 0.1 R ⊕ , HIP 41378 f has an extremely low bulk density (0.09 ± 0.02 g cm −3 ). We measure the transit depth with a median precision of 84 ppm in 30 spectrophotometric channels with uniformlysized widths of 0.018 µm. Within this level of precision, the spectrum shows no evidence of absorption from gaseous molecular features between 1.1-1.7 µm. Comparing the observed transmission spectrum to a suite of 1D radiative-convective-thermochemical-equilibrium forward models, we rule out clear, low-metallicity atmospheres and find that the data prefer high-metallicity atmospheres or models with an additional opacity source, such as high-altitude hazes and/or circumplanetary rings. We explore the ringed scenario for HIP 41378 f further by jointly fitting the K2 and HST light curves to constrain the properties of putative rings. We also assess the possibility of distinguishing between hazy, ringed, and high-metallicity scenarios at longer wavelengths with JWST. HIP 41378 f provides a rare opportunity to probe the atmospheric composition of a cool giant planet spanning the gap in temperature, orbital separation, and stellar irradiation between the Solar System giants, directly imaged planets, and the highly-irradiated hot Jupiters traditionally studied via transit spectroscopy.

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Hubble WFC3 Spectroscopy of the Habitable-zone Super-Earth LHS 1140 b

Cited by 83 publications

References 84 publications

Atmospheres of Rocky Exoplanets

Atmospheres of Rocky Exoplanets

Detecting Biosignatures in the Atmospheres of Gas Dwarf Planets with the James Webb Space Telescope

The First Near-Infrared Transmission Spectrum of HIP 41378 f, a Low-Mass Temperate Jovian World in a Multi-Planet System

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