J/ApJ/940/L35 HAT-P-18b JWST NIRISS transmission spectrum (Fu+, 2022)
Water and an escaping helium tail detected in the hazy and methane-depleted
atmosphere of HAT-P-18b from JWST NIRISS/SOSS.
Fu G., Espinoza N., Sing D.K., Lothringer J.D., Dos Santos L.A.,
Rustamkulov Z., Deming D., Kempton E.M.-R., Komacek T.D., Knutson H.A.,
Albert L., Pontoppidan K., Volk K., Filippazzo J.
<Astrophys. J., 940, L35 (2022)>
=2022ApJ...940L..35F 2022ApJ...940L..35F
ADC_Keywords: Exoplanets; Spectra, infrared
Keywords: Exoplanet atmospheres ; Exoplanet atmospheric composition ;
Exoplanet astronomy
Abstract:
JWST is here. The early release observation (ERO) program provides us
with the first look at the scientific data and the spectral
capabilities. One of the targets from the ERO is HAT-P-18b, an
inflated Saturn-mass planet with an equilibrium temperature of ∼850K.
We present the NIRISS/SOSS transmission spectrum of HAT-P-18b from
0.6 to 2.8µm and reveal the planet in the infrared beyond 1.6µm
for the first time. From the spectrum, we see clear water and escaping
helium tail features in an otherwise very hazy atmosphere. Our free
chemistry retrievals with ATMO show moderate Bayesian evidence (3.79)
supporting the presence of methane, but the spectrum does not display
any clearly identifiable methane absorption features. The retrieved
methane abundance is ∼2 orders of magnitude lower than that of solar
composition. The methane-depleted atmosphere strongly rejects simple
equilibrium chemistry forward models with solar metallicity and a C/O
ratio and disfavors high metallicity (100 times) and a low C/O ratio
(0.3). This calls for additional physical processes such as vertical
mixing and photochemistry, which can remove methane from the
atmosphere.
Description:
This data set was collected as part of the early release observation
program (program ID: 2734). A transit of HAT-P-18b was observed using
the JWST Near Infrared Imager and Slitless Spectrograph single object
slitless spectroscopy (NIRISS/SOSS), which covers ∼0.6 to 2.8um on
2022 June 13 with the GR700XD grism and the CLEAR filter. A total of
7.15hr of time series observation was taken.
Objects:
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RA (ICRS) DE Designation(s)
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17 05 23.14 +33 00 44.9 HAT-P-18b = TOI-2127.01
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 17 1021 HAT-P-18b transmission spectrum
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See also:
VI/151 : Search for radio emission from giant exoplanets (Griessmeier, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/MNRAS/411/L46 : Exoplanet magnetic fields (Vidotto+, 2011)
J/ApJ/726/52 : HAT-P-18 and HAT-P-19 follow-up (Hartman+, 2011)
J/AJ/144/139 : HAT-P-39, HAT-P-40, and HAT-P-41 follow-up (Hartman+, 2012)
J/A+A/552/A119 : Planet-star and moon-planet interaction (Saur+, 2013)
J/ApJ/764/18 : Frequencies of giant exoplanets (Le Bihan+, 2013)
J/ApJ/766/9 : GALEX observations of exoplanet host stars (Shkolnik, 2013)
J/ApJ/771/107 : Spectroscopy of faint KOI stars (Everett+, 2013)
J/ApJ/796/48 : Exoplanet targets with Palomar/TripleSpec (Zellem+, 2014)
J/A+A/573/A90 : STAGGER-grid of 3D stellar models. IV. (Magic+, 2015)
J/ApJ/831/64 : Mass-metallicities for giant planets (Thorngren+, 2016)
J/ApJ/834/17 : Mass & rad of planets, moons, low mass stars (Chen+, 2017)
J/MNRAS/468/3907 : HAT-P-18b wavelength binned light curves (Kirk+, 2017)
J/ApJS/239/14 : Revised exoplanet radii from Gaia DR2 (Johns+, 2018)
J/A+A/630/A135 : Beyond exoplanet mass-radius relations (Ulmer-Moll+, 2019)
J/ApJ/874/L31 : Giant planet bulk & atm. metallicities (Thorngren+, 2019)
J/ApJ/893/L29 : Hot Jupiter predicted period changes (Bouma+, 2020)
J/AJ/159/41 : ∼550 exoplanet data using a neural network (Tasker+, 2020)
J/AJ/163/228 : TESS exoplanet Limb-darkening coefficients (Patel+, 2022)
J/ApJS/258/40 : ExoClock project. II. Exoplanet ephemerides (Kokori+, 2022)
J/ApJS/265/4 : ExoClock project. III. Exoplanet ephemerides (Kokori+, 2023)
J/AJ/165/104 : Emergent sp. IR fluxes of 122 hot Jupiters (Deming+, 2023)
J/AJ/165/264 : 130 Stellar and planetary parameters (Bennett+, 2023)
J/ApJS/270/14 : Transit times of hot Jupiters from TESS (Wang+, 2024)
J/AJ/167/1 : Transit depth variability with TESS (Wang+, 2024)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 F6.4 um lambda [0.6/2.83] Wavelength mid-point
8- 12 I5 ppm Depth [17411/20807] Transit depth
14- 17 I4 ppm e_Depth [126/1009] Uncertainty in Depth
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Nov-2024