Photonic Transmission Spectroscopy of WASP-39b with JWST

1. Scientific Context (Photonics)

Transmission spectroscopy measures wavelength-dependent photon attenuation during planetary transit.

• Photon–molecule interaction
• Absorption cross-sections σ(λ)
• Instrument-limited spectral resolution

2. Target Properties

• Mass: 0.28 M_J
• Radius: 1.27 R_J
• g ≈ 8.5 m s⁻²
• T_eq ≈ 1100 K

Low gravity results in a large atmospheric scale height, enhancing photonic detectability.

3. JWST Observations

• NIRISS SOSS: 0.6–2.8 μm
• NIRSpec PRISM: 0.6–5.0 μm

Data correspond to binned transmission spectra from public JWST ERS releases, shown with 1σ uncertainties.

4. Transmission Spectrum

Distinct absorption bands correspond to molecular opacities and Rayleigh scattering.

5. Forward Atmospheric Model

Isothermal hydrostatic atmosphere: H = k_BT / (μg)

• Molecular opacity: H₂O, CO₂
• Rayleigh scattering ∝ λ⁻⁴
• Grey cloud deck (P_cloud)

6. Residuals & Fit Quality

7. Instrument Consistency

Independent instruments show consistent photonic signatures, validating calibration.

8. Photonic Interpretation

• Absorption depth ∝ effective optical depth
• CO₂ at 4.3 μm detected at high significance
• Photon noise dominates outside bands

9. Conclusions

• JWST enables molecular-scale photonic sensing
• WASP-39b shows clear H₂O and CO₂ absorption
• Simple forward models reproduce observables