J/AJ/169/38 HD 189733b NIRCam transmission & emission spectra (Zhang+, 2025)
Retrievals on NIRCam transmission and emission spectra of HD 189733b with
PLATON 6, a GPU code for the JWST era.
Zhang M., Paragas K., Bean J.L., Yeung J., Chachan Y., Greene T.P.,
Lunine J., Deming D.
<Astron. J., 169, 38 (2025)>
=2025AJ....169...38Z 2025AJ....169...38Z
ADC_Keywords: Exoplanets; Spectra, infrared
Keywords: Exoplanet atmospheres ; James Webb Space Telescope ;
Exoplanet atmospheric composition
Abstract:
We present the 2.4-5.0um JWST/NIRCam emission spectrum of HD
189733b, along with an independent re-reduction of the previously
published transmission spectrum at the same wavelengths. We use an
upgraded version of PLanetary Atmospheric Tool for Observer Noobs
(PLATON) to retrieve atmospheric parameters from both geometries. In
transit, we obtain [M/H]=0.53-0.12+0.13 and C/O=0.41-0.12+0.13,
assuming a power-law haze and equilibrium chemistry with methane
depletion. In eclipse, we obtain [M/H]=0.68-0.11+0.15 and
C/O=0.43-0.05+0.06, assuming a clear atmosphere and equilibrium
chemistry without methane depletion. These results are consistent with
each other, and with a rerun of our previously published joint
retrieval of Hubble Space Telescope and Spitzer transmission and
emission spectra. Accounting for methane depletion decreases the C/O
ratio by 0.14/0.04 (transmission/emission), but changing the limb
cloud parameterization does not affect the C/O ratio by more than
0.06. We detect H2O, CO2, CO, and H2S in both the NIRCam
transmission and emission spectra, find that methane is depleted on
the terminator, and confirm with VULCAN that photochemistry is a
potential cause of this depletion. We also find tentative (1.8σ)
evidence of a dayside thermal inversion at millibar pressures.
Finally, we take this opportunity to introduce a new version of
PLATON. PLATON 6 supports GPU computation, speeding up the code up to
10x. It also supports free retrievals using both volume mixing ratio
and centered-log ratio priors; emission from planetary surfaces of
different compositions; updated opacities at improved resolution; and
Pareto smoothed importance sampling leave-one-out cross-validation.
Description:
The JWST/NIRCam Grism Time Series observations we analyze consist of one
transit and one eclipse in each of the F322W2 (2.4-3.95um) and
F444W (3.90-5.00um) bandpasses, for a total of four visits. Note
the small 0.05um overlap between our conservatively defined
bandpasses. The observations come from three programs: GO 1633 (PI:
Drake Deming), which observed both transits; GTO 1274 (PI: Jonathan
Lunine), which observed the F322W2 eclipse; and GTO 1185 (PI: Thomas
Greene), which observed the F444W eclipse. The transits have been
previously published in Fu+(2024Natur.632..752F 2024Natur.632..752F).
The transit/eclipse duration is 1.84±0.04hr
(Addison+, 2019PASP..131k5003A 2019PASP..131k5003A), so all observations have ample
baseline on both sides. All observations were taken within a month of
each other, and all except the F444W eclipse were taken within 4 days.
The gap between the two transits (4.4 days, or 2 orbital periods) is
37% of the stellar rotation period (Henry+2008, J/AJ/135/68), meaning
that the side of the star facing the Earth, and therefore the pattern
of spots and faculae, is expected to be very different.
The filter, date, and duration of each observation for transit and
eclipse are as follows: Transit with F322W2 on 2022 Aug 28 for 5.9h,
Transit with F444W on 2022 Aug 25 for 6hr, Eclipse with F322W2 on 2022
Aug 26 for 5.6 hr, and Eclipse with F444W on 2022 Sep 28 for 5.6hr.
Objects:
---------------------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------------------
20 00 43.71 +22 42 39.0 HD 189733b = HD 189733b (ok)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig7.dat 48 106 Best-fit transmission and emission spectra of
HD 189733b (data behind Figure 7)
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See also:
J/AJ/135/68 : HD 189733 differential light curve (Henry+, 2008)
J/ApJ/795/166 : Extrasolar planet HD 189733b whitelight curve (Crouzet+, 2014)
J/ApJ/791/55 : HD 189733b in transit light curve (McCullough+, 2014)
J/A+A/573/A90 : STAGGER-grid of 3D stellar models. IV. (Magic+, 2015)
J/A+A/589/A21 : K-H2 line shapes for cool brown dwarfs spectra (Allard+, 2016)
J/A+A/619/A96 : HD189733 spectral variability (Kohl+, 2018)
J/ApJS/260/3 : 25 hot-Jupiter properties from HST & Spitzer (Changeat+, 2022)
J/ApJ/940/L35 : HAT-P-18b JWST NIRISS transmission spectrum (Fu+, 2022)
J/MNRAS/510/903 : ExoMol molecular line lists. XLIV. SiO (Yurchenko+, 2022)
J/AJ/165/5 : SDSS ugri photometry of HD 189733 (Gardner-Watkins+, 2023)
J/AJ/165/104 : Emergent spectral IR fluxes of 122 hot Jupiters (Deming+, 2023)
Byte-by-byte Description of file: fig7.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Type Spectrum type (1)
14- 17 F4.2 um MinWave [2.4/4.95] Minimum wavelength of the bin
19- 22 F4.2 um MaxWave [2.45/5] Maximum wavelength of the bin
24- 32 E9.3 --- Depth [4.2e-4/2.5e-2] Median depth in wavelength bin
34- 40 E7.1 --- e_Depth [2e-5/5.3e-5] Lower uncertainty in Depth
42- 48 E7.1 --- E_Depth [2e-5/5.1e-5] Upper uncertainty in Depth
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Note (1): Types as follows:
Transmission = 53 occurrences
Emission = 53 occurrences
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History:
From electronic version of the journal
(End) Prepared by [AAS], Robin Leichtnam [CDS] 12-Nov-2025