{"paper":{"title":"Toward a New Geometric Distance to the Active Galaxy NGC4258: I. VLBI Monitoring of Water Maser Emission","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"A. L. Argon, E. M. L. Humphreys (Harvard-Smithsonian Center for Astrophysics), J. M. Moran, L. J. Greenhill, M. J. Reid","submitted_at":"2007-01-12T22:52:31Z","abstract_excerpt":"We report a three year, 18 epoch, VLBI monitoring study of H2O masers in the sub-parsec, warped, accretion disk within the NGC4258 AGN. Our immediate goals are to trace the geometry of the underlying disk, track rotation via measurement of proper motion, and ascertain the radii of masers for which centripetal acceleration may be measured separately. The monitoring includes ~ 4 times as many epochs, ~ 3 times denser sampling, and tighter control over sources of systematic error than earlier VLBI investigations. Coverage of a ~ 2400 km/s bandwidth has also enabled mapping of molecular material ~"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/0701396","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"}