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2025
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| Online Access: | https://doi.org/10.5281/zenodo.17459254 |
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| _version_ | 1866901307362639872 |
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| author | Nawaz, Ali |
| author_facet | Nawaz, Ali |
| contents | <p>Ligand field theory (LFT) was applied to publicly available HST WFC3 transmission spectra of<br>K2-18b to examine whether visible-band d–d orbital transitions might indicate metal-bearing species.<br>Within current sensitivity limits, no statistically significant absorption features attributable to Fe3+<br>(e.g., [Fe(H2O)6]3+ near 510 nm) or TiO were identified in the 550–650 nm range after multi-HDU<br>stacking, smoothing, and Gaussian fitting. The visible spectrum appears broadly consistent with<br>a scattering continuum, suggestive of high-altitude haze. This non-detection is consistent with a<br>hydrogen-rich, possibly Hycean-like atmosphere inferred from recent JWST studies (e.g., Madhusudhan et al. 2023; Arney et al. 2023), and highlight the need for future coordinated multi-wavelength<br>observations to constrain metal transitions and photochemical pathways in sub-Neptune atmospheres.</p> |
| format | Recurso digital |
| id | zenodo_https___doi_org_10_5281_zenodo_17459254 |
| institution | Zenodo |
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| publishDate | 2025 |
| publisher | Zenodo |
| record_format | zenodo |
| spellingShingle | A Ligand Field Perspective on the Visible Spectrum of K2-18b: Search for Fe3+ and TiO Signatures Nawaz, Ali <p>Ligand field theory (LFT) was applied to publicly available HST WFC3 transmission spectra of<br>K2-18b to examine whether visible-band d–d orbital transitions might indicate metal-bearing species.<br>Within current sensitivity limits, no statistically significant absorption features attributable to Fe3+<br>(e.g., [Fe(H2O)6]3+ near 510 nm) or TiO were identified in the 550–650 nm range after multi-HDU<br>stacking, smoothing, and Gaussian fitting. The visible spectrum appears broadly consistent with<br>a scattering continuum, suggestive of high-altitude haze. This non-detection is consistent with a<br>hydrogen-rich, possibly Hycean-like atmosphere inferred from recent JWST studies (e.g., Madhusudhan et al. 2023; Arney et al. 2023), and highlight the need for future coordinated multi-wavelength<br>observations to constrain metal transitions and photochemical pathways in sub-Neptune atmospheres.</p> |
| title | A Ligand Field Perspective on the Visible Spectrum of K2-18b: Search for Fe3+ and TiO Signatures |
| url | https://doi.org/10.5281/zenodo.17459254 |