{"paper":{"title":"SN 2021foa: The \"Flip-Flop\" Type IIn / Ibn supernova","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.HE","authors_text":"A. Dhara, A. Gagliano, A. Rest, A. Sarangi, C.-C. Lin, C. D. Kilpatrick, C. Gall, C. L. Ransome, C. R. Angus, D. A. Coulter, D. Farias, D. O. Jones, E. Ramirez-Ruiz, G. Narayan, H. Gao, H .M. L. Perkins, J. Hjorth, J. J. Swift, K. Auchettl, K. E. Clever, K. Taggart, K. W. Davis, L. Izzo, M. R. Siebert, N. Khetan, P. Wrubel, R. Foley, R. Yarza, S. Rest, S. Tinyanont, T. J. L. de Boer, V. A. Villar","submitted_at":"2024-09-02T16:24:22Z","abstract_excerpt":"We present a comprehensive analysis of the photometric and spectroscopic evolution of SN~2021foa, unique among the class of transitional supernovae for repeatedly changing its spectroscopic appearance from hydrogen-to-helium-to-hydrogen-dominated (IIn-to-Ibn-to-IIn) within 50 days past peak brightness. The spectra exhibit multiple narrow ($\\approx$ 300--600~km~s$^{-1}$) absorption lines of hydrogen, helium, calcium and iron together with broad helium emission lines with a full-width-at-half-maximum (FWHM) of $\\sim 6000$~km~s$^{-1}$. For a steady, wind-mass loss regime, light curve modeling res"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2409.01359","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2409.01359/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}