{"paper":{"title":"A New Approach to the Low Frequency Stochastic Gravitational Wave Background: Constraints from Quasars and the Astrometric Hellings-Downs Curve","license":"http://creativecommons.org/licenses/by/4.0/","headline":"","cross_cats":["gr-qc"],"primary_cat":"astro-ph.CO","authors_text":"Jeremy Darling","submitted_at":"2024-12-11T18:27:15Z","abstract_excerpt":"We present new astrometric constraints on the stochastic gravitational wave background and construct the first astrometric Hellings-Downs curve using quasar proper motions. From quadrupolar vector spherical harmonic fits to the Gaia proper motions of 1,108,858 quasars, we obtain a frequency-integrated upper limit on the gravitational wave energy density, $h_{70}^2\\Omega_{GW} \\leq 0.023$ (95% confidence limit), for frequencies between 11.2 nHz and $3.1\\times10^{-9}$ nHz ($1.33/t_0$). However, from the astrometric Hellings-Downs curve that describes the correlated proper motions between 2,104,60"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2412.08605","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/2412.08605/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"}