{"paper":{"title":"Spectroscopic Observations and Analysis of the Peculiar SN 1999aa","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"A. Amadon, A. Conley, A. G. Kim, A. Goobar, A. L. Spadafora, A. Mourao, B. C. Lee, B. E. Schaefer, B. Frye, B. Goldman, C. Balland, C. Lidman, D. A. Howell, D. E. Groom, D. Hardin, D. Kasen, E. L. Gates, E. Smith, G. Aldering, G. Blanc, G. Folatelli, G. Garavini, G. Goldhaber, G. J. Miller, G. Sainton, G. T. Richards, H. Newberg, I. M. Hook, J. Haissinski, J. Mendez, J. Raux, J. Rich, K. Schahmaneche, L. Wang, M. Moniez, M. S. Burns, N. A. Walton, N. Regnault, O. Perdereau, P. Astier, P. E. Nugent, P. Ruiz-Lapuente, R. A. Knop, R. Amanullah, R. Ellis, R. Gibbons, R. Pain, R. Quimby, S. E. Deustua, S. Fabbro, S. Kent, S. Nobili, S. Perlmutter, T. Dahlen, V. Prasad, V. Stanishev, W. M. Wood-Vasey (The Supernova Cosmology Project), X. Fan","submitted_at":"2004-04-20T19:35:12Z","abstract_excerpt":"We present an extensive new time-series of spectroscopic data of the peculiar SN 1999aa in NGC 2595. Our data set includes 25 optical spectra between -11 and +58 days with respect to B-band maximum light, providing an unusually complete time history. The early spectra resemble those of a SN 1991T-like object but with a relatively strong Ca H&K absorption feature. The first clear sign of Si II 6355, characteristic of Type Ia supernovae, is found at day -7 and its velocity remains constant up to at least the first month after B-band maximum light. The transition to normal-looking spectra is foun"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/0404393","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"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"}