{"paper":{"title":"Deep Adaptive Optics Imaging Rules Out a Helium Star Companion to PSR J1928+1815","license":"http://creativecommons.org/licenses/by/4.0/","headline":"Deep adaptive optics imaging rules out a helium star companion to PSR J1928+1815.","cross_cats":["astro-ph.HE"],"primary_cat":"astro-ph.SR","authors_text":"Jim Fuller, Kareem El-Badry, Pranav Nagarajan, Thomas M. Tauris, Yunlang Guo","submitted_at":"2026-04-03T18:28:26Z","abstract_excerpt":"PSR J1928+1815 is a 10.55 ms millisecond pulsar in a 3.6 hr orbit with a massive ($1.0$-$1.6\\,M_{\\odot}$) companion that produces extended radio eclipses. The companion, proposed to be a stripped helium star, is undetected in optical and infrared surveys. We present deep near-infrared imaging using Keck/NIRC2 with laser guide star adaptive optics. No source is detected at the pulsar position down to a $5\\sigma$ limit of $K_s \\approx 21.3$. Using stripped-star atmosphere models and conservative extinction estimates, we show that any plausible helium star companion would have been detected, ruli"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"No source is detected at the pulsar position down to a 5σ limit of Ks ≈ 21.3. Using stripped-star atmosphere models and conservative extinction estimates, we show that any plausible helium star companion would have been detected, ruling out this interpretation.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The stripped-star atmosphere models accurately predict the near-infrared brightness for companions in the 1.0–1.6 M⊙ range, and the adopted extinction values are sufficiently conservative; if either is inaccurate, the non-detection would not fully exclude a helium star.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Deep Keck/NIRC2 adaptive optics imaging rules out a helium star companion to PSR J1928+1815, supporting a massive white dwarf with possible wind-driven eclipses.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Deep adaptive optics imaging rules out a helium star companion to PSR J1928+1815.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"610ffb5d9d65f1771121a68ba1ba6a17e96b7db92307b419e867d493f0833a60"},"source":{"id":"2604.03385","kind":"arxiv","version":2},"verdict":{"id":"2a0affe5-4303-4483-8754-2dd8adab0b3e","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-13T18:04:44.235340Z","strongest_claim":"No source is detected at the pulsar position down to a 5σ limit of Ks ≈ 21.3. Using stripped-star atmosphere models and conservative extinction estimates, we show that any plausible helium star companion would have been detected, ruling out this interpretation.","one_line_summary":"Deep Keck/NIRC2 adaptive optics imaging rules out a helium star companion to PSR J1928+1815, supporting a massive white dwarf with possible wind-driven eclipses.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The stripped-star atmosphere models accurately predict the near-infrared brightness for companions in the 1.0–1.6 M⊙ range, and the adopted extinction values are sufficiently conservative; if either is inaccurate, the non-detection would not fully exclude a helium star.","pith_extraction_headline":"Deep adaptive optics imaging rules out a helium star companion to PSR J1928+1815."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2604.03385/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":2,"snapshot_sha256":"29c3fa45fc9e4090910caf40a4856c5a398924a6831b75f8923e6d8576700219"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}