{"paper":{"title":"JWST COMPASS Program: The 3--5$\\mu$m transmission spectrum of LTT 1445 A b","license":"http://creativecommons.org/licenses/by/4.0/","headline":"The JWST 3-5 micron transmission spectrum of LTT 1445 A b shows no detectable atmospheric features, limiting metallicity to at least 350 times solar under grey cloud models.","cross_cats":[],"primary_cat":"astro-ph.EP","authors_text":"Angie Wolfgang, Annabella Meech, Anna Gagnebin, Artyom Aguichine, Hannah R. Wakeford, Jea Adams Redai, Jeff Valenti, Johanna Teske, Katherine A. Bennett, Lili Alderson, Mercedes L\\'opez-Morales, Munazza K. Alam, Natalie M. Batalha, Natasha E. Batalha, Nicholas F. Wogan, Nicole Wallack, Peter Gao, Sarah E. Moran, Tyler Gordon","submitted_at":"2026-05-14T16:05:17Z","abstract_excerpt":"The search for an atmosphere on the closest rocky M dwarf planet, LTT 1445 A b, has been the subject of intense investigation from both the ground and space. Here, we present the first JWST transmission spectrum of LTT 1445 A b using a single visit spanning 3-5~$\\mu$m using NIRSpec/G395H. We conduct two independent reductions of the data using both the Eureka! and ExoTiC-JEDI pipelines. Overall, we measure the NRS1 transit depths to a median precision of $\\sim23$~ppm in 41 spectroscopic channels with uniform widths of 30 pixels ($\\sim$ 0.02 $\\mu$m), and the NRS2 transit depths to $\\sim36$~ppm "},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"We rule out any statistically significant spectral features at this precision and place limits on atmospheric metallicity using a grid of chemical equilibrium models with grey opaque clouds. Using NIRSpec/G395H alone, we can place limits on the atmospheric metallicity of ≳350× Solar when the opaque pressure level is greater than 0.01 bars.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The assumption that grey opaque clouds and chemical equilibrium accurately represent all plausible atmospheres on this planet, such that a non-detection truly rules out lower metallicities rather than reflecting model incompleteness or unaccounted systematics in the single-visit data.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"JWST NIRSpec observations of LTT 1445 A b yield a featureless 3-5μm transmission spectrum, limiting atmospheric metallicity to ≳350× solar under grey-cloud models.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"The JWST 3-5 micron transmission spectrum of LTT 1445 A b shows no detectable atmospheric features, limiting metallicity to at least 350 times solar under grey cloud models.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"74d2208eb4dad725f7d7a1bf7e18d441af331319ae93ef3f2ea3b220395b12b9"},"source":{"id":"2605.15003","kind":"arxiv","version":1},"verdict":{"id":"09192998-2a5a-402e-b695-80597d711438","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-15T03:11:47.084160Z","strongest_claim":"We rule out any statistically significant spectral features at this precision and place limits on atmospheric metallicity using a grid of chemical equilibrium models with grey opaque clouds. Using NIRSpec/G395H alone, we can place limits on the atmospheric metallicity of ≳350× Solar when the opaque pressure level is greater than 0.01 bars.","one_line_summary":"JWST NIRSpec observations of LTT 1445 A b yield a featureless 3-5μm transmission spectrum, limiting atmospheric metallicity to ≳350× solar under grey-cloud models.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The assumption that grey opaque clouds and chemical equilibrium accurately represent all plausible atmospheres on this planet, such that a non-detection truly rules out lower metallicities rather than reflecting model incompleteness or unaccounted systematics in the single-visit data.","pith_extraction_headline":"The JWST 3-5 micron transmission spectrum of LTT 1445 A b shows no detectable atmospheric features, limiting metallicity to at least 350 times solar under grey cloud models."},"references":{"count":96,"sample":[{"doi":"10.3847/1538-3881/adee92","year":2025,"title":"Adams Redai, J., Wogan, N., Wallack, N. L., et al. 2025, AJ, 170, 219, doi: 10.3847/1538-3881/adee92","work_id":"41c4ee83-f125-47e3-85a3-bcd42f38cf17","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.3847/1538-3881/ad8eb5","year":2025,"title":"K., Gao, P., Adams Redai, J., et al","work_id":"c3b026e5-251c-41b3-9938-eb9e2e1d6b9e","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.5281/zenodo.7185855","year":2022,"title":"2022, Exo-TiC/ExoTiC-JEDI: v0.1-beta-release, v0.1, Zenodo, Zenodo, doi: 10.5281/zenodo.7185855","work_id":"323f6c5d-016f-4f66-95b4-8818e39aa98e","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.1038/s41586-022-05591-3","year":2023,"title":"Alderson, L., Wakeford, H. R., Alam, M. K., et al. 2023, Nature, 614, 664, doi: 10.1038/s41586-022-05591-3","work_id":"e3ac108e-d949-474a-b1c0-a8927dcb6054","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.3847/1538-3881/ad32c9","year":2024,"title":"Alderson, L., Batalha, N. E., Wakeford, H. R., et al. 2024, AJ, 167, 216, doi: 10.3847/1538-3881/ad32c9","work_id":"5dac14df-c1dc-462b-871a-24a604ec288e","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":96,"snapshot_sha256":"7136a370d7ecb07bc9faba558f293f0e3d7dcec2269e0375c9dfc5a914efdf1d","internal_anchors":0},"formal_canon":{"evidence_count":1,"snapshot_sha256":"521783d1a6cc5bf6692ab3cc33bbb1c97caa3ee3ec46a402033cdaf62773c584"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}