{"paper":{"title":"Tracing the kinematic perturbations of the Milky Way spiral arms with APOGEE DR17 and Gaia DR3","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"A revised model including both sine and cosine radial-velocity terms reproduces Milky Way stellar streaming motions to within 2 percent, constraining spiral pitch angle to about 10 degrees.","cross_cats":[],"primary_cat":"astro-ph.GA","authors_text":"Hao Tian, Iulia T. Simion, Shuting Fan, Xi-Can Tang, Zhijian Luo, Zhi Li, Zi-Qi Li","submitted_at":"2026-05-11T07:10:42Z","abstract_excerpt":"Aims. We constrain the dynamical perturbations of the spiral arms in the Milky Way disk, based on the non-axisymmetric streaming motions of RGB stars revealed by APOGEE and \\textit{Gaia}.\n  Methods. We develop a revised steady-state radial-velocity response model that incorporates both the \\(V_{R,\\sin}\\) and the dynamically important \\(V_{R,\\cos}\\) components for a two-armed logarithmic spiral potential. The model is validated using orbit integrations with \\texttt{AGAMA} and Bayesian parameter recovery with \\texttt{dynesty}, and is applied to the smoothed two-dimensional radial-velocity field "},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"The revised model reproduces the phase and amplitude of the mock radial-velocity field to the ~2% level, substantially improving upon earlier V_R,sin-only formulations. Applied to the observational data, it yields a robust pitch angle of p ≃ 10° and a local surface density contrast of ξ ≃ 5--18% at the solar radius. The observed kinematics constrain the spiral pattern speed to Ω_p ≈ 10--20 km s^{-1} kpc^{-1}.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The assumption that the observed velocity field is dominated by the steady-state response to a two-armed logarithmic spiral potential, with resonances properly accounted for and no major contributions from other non-axisymmetric perturbations or time-dependent effects.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"A revised steady-state radial-velocity response model with both V_R,sin and V_R,cos terms constrains the Milky Way's two-armed spiral to a pitch angle of ~10° and local density contrast of 5-18% at the solar radius.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"A revised model including both sine and cosine radial-velocity terms reproduces Milky Way stellar streaming motions to within 2 percent, constraining spiral pitch angle to about 10 degrees.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"6fb1c09d01816f617c003d2c99d974e13cb2874dd5f51fc8b22f68e2325d8da2"},"source":{"id":"2605.10092","kind":"arxiv","version":2},"verdict":{"id":"e8523356-3310-4594-880b-da4414381274","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-12T02:50:28.490734Z","strongest_claim":"The revised model reproduces the phase and amplitude of the mock radial-velocity field to the ~2% level, substantially improving upon earlier V_R,sin-only formulations. Applied to the observational data, it yields a robust pitch angle of p ≃ 10° and a local surface density contrast of ξ ≃ 5--18% at the solar radius. The observed kinematics constrain the spiral pattern speed to Ω_p ≈ 10--20 km s^{-1} kpc^{-1}.","one_line_summary":"A revised steady-state radial-velocity response model with both V_R,sin and V_R,cos terms constrains the Milky Way's two-armed spiral to a pitch angle of ~10° and local density contrast of 5-18% at the solar radius.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The assumption that the observed velocity field is dominated by the steady-state response to a two-armed logarithmic spiral potential, with resonances properly accounted for and no major contributions from other non-axisymmetric perturbations or time-dependent effects.","pith_extraction_headline":"A revised model including both sine and cosine radial-velocity terms reproduces Milky Way stellar streaming motions to within 2 percent, constraining spiral pitch angle to about 10 degrees."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2605.10092/integrity.json","findings":[],"available":true,"detectors_run":[{"name":"claim_evidence","ran_at":"2026-05-20T06:42:01.049305Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"ai_meta_artifact","ran_at":"2026-05-19T15:41:05.788028Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"doi_title_agreement","ran_at":"2026-05-19T12:01:17.826932Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"doi_compliance","ran_at":"2026-05-19T09:41:36.448230Z","status":"completed","version":"1.0.0","findings_count":0}],"snapshot_sha256":"37077c0f2d4017d882c302b9c0cbcc6c52fb1294a5348a6caf945a0903d152e7"},"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"}