{"paper":{"title":"REM observations of GRB 060418 and GRB 060607A: the onset of the afterglow and the initial fireball Lorentz factor determination","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"A. Monfardini, A. Pizarro, D. Guetta, D. Malesani, D. Rizzuto, E.J.A. Meurs, E. Molinari, E. Palazzi, E. Pian, F. D'Alessio, F.M. Zerbi, F. Vitali, G. Chincarini, G. Ihle, G. Malaspina, G. Tagliaferri, G. Tosti, J. Valenzuela, L.A. Antonelli, L. Gonzalez, L. Nicastro, L. Norci, L. Stella, M. Stefanon, N. Masetti, P.A. Ward, P. Conconi, P. D'Avanzo, P. Goldoni, P. Sinclair, S. Campana, S. Covino, S.D. Vergani, S. Piranomonte, V. Testa","submitted_at":"2006-12-20T21:00:03Z","abstract_excerpt":"Gamma-ray burst (GRB) emission is believed to originate in highly relativistic fireballs. Currently, only lower limits were securely set to the initial fireball Lorentz factor Gamma_0. We aim to provide a direct measure of Gamma_0. The early-time afterglow light curve carries information about Gamma_0, which determines the time of the afterglow peak. We have obtained early observations of the near-infrared afterglows of GRB 060418 and GRB 060607A with the REM robotic telescope. For both events, the afterglow peak could be clearly singled out, allowing a firm determination of the fireball Loren"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/0612607","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/astro-ph/0612607/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"}