{"paper":{"title":"M74 X-1 (CXOU J013651.1+154547): An Extremely Variable Ultraluminous X-Ray Source","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"2), (2) University of Leicester, 3), (3) MIT Kavli Institute for Astrophysics, A.H. Prestwich (1) ((1) Harvard-Smithsonian Center for Astrophysics, M.I. Krauss (1, M.R. Garcia (1), R.E. Kilgard (1, Space Research), T.P. Roberts (2)","submitted_at":"2005-05-12T15:47:50Z","abstract_excerpt":"Ultraluminous X-ray sources (ULXs) have been described variously as the most luminous normal X-ray binaries, as hypernovae, and as \"intermediate-mass\" black holes with masses of hundreds to thousands of solar masses. We present results on M74 X-1 (CXOU J013651.1+154547), a ULX in the nearby spiral galaxy M74 (NGC 628), from observations by Chandra and XMM-Newton. M74 X-1is a persistent source which exhibits extreme variability and changes in spectral state on timescales of several thousand seconds. Its variability timescales and behavior resemble some Galactic microquasars. This suggests that "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/0505260","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":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/astro-ph/0505260/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"}