{"paper":{"title":"When A Standard Candle Flickers","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.HE","authors_text":"Andreas von Kienlin, Ascension Camero-Arranz (NSSTC), Charles A. Meegan (USRA), Chryssa Kouveliotou (NASA/MSFC), Colleen A. Wilson-Hodge (NASA/MSFC), Doug Swartz (USRA), Erik Kuulkers (ESA/ESAC), Gary L. Case (LSU), Gerald K. Skinner (UMD/CRESST/NASA/GSFC), Hans A. Krimm (CRESST/NASA/GSFC/USRA), James C. Rodi (LSU), Jochen Greiner (MPE), Keith Jahoda (NASA/GSFC), Lorenzo Natalucci (INAF-IASF), Mark H. Finger (USRA), Michael L. Cherry (LSU), Michael S. Briggs (UAH), Neil Gehrels (NASA/GSFC), Nikolai Shaposhnikov, Peter Jenke (NPP/NASA/MSFC), P. Narayana Bhat, R. Marc Kippen (LANL), Robert Preece (UAH), Roland Diehl, Valerie Connaughton (UAH), Vandiver Chaplin, Wayne H. Baumgartner (NASA/CRESST) Elif Beklen (METU/SDU), William S. Paciesas, Xiao-Ling Zhang (MPE)","submitted_at":"2010-10-13T15:04:07Z","abstract_excerpt":"The Crab Nebula is the only hard X-ray source in the sky that is both bright enough and steady enough to be easily used as a standard candle. As a result, it has been used as a normalization standard by most X-ray/gamma ray telescopes. Although small-scale variations in the nebula are well-known, since the start of science operations of the Fermi Gamma-ray Burst Monitor (GBM) in August 2008, a ~ 7% (70 mcrab) decline has been observed in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline is independently confirmed with three other "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1010.2679","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":""},"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"}