{"paper":{"title":"Radio Emission from Fast Blue Optical Transients Powered by Trans-relativistic Shocks in Confined Circumstellar Material","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"Trans-relativistic shocks crossing a confined circumstellar shell explain the radio diversity of fast blue optical transients.","cross_cats":[],"primary_cat":"astro-ph.HE","authors_text":"Jia-Sen Zhang, Liang-Duan Liu, Yun-Wei Yu, Zhao-Sheng Zhang","submitted_at":"2026-05-17T06:25:44Z","abstract_excerpt":"Fast blue optical transients (FBOTs) are luminous, rapidly evolving explosions whose radio emission provides a sensitive probe of shock interaction and the circumstellar material (CSM) surrounding the progenitor. However, the origin of their diverse radio light-curve morphologies, especially the very steep post-peak declines seen in several well-sampled events, remains unclear. We present a forward-shock synchrotron model in which mildly relativistic ejecta interact with a dense but radially confined CSM. The CSM is described by a broken power-law density profile, and the radio emission is mod"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"their radio diversity can be explained by shock propagation through a finite CSM shell. The early radio evolution is regulated by absorption, while the rapid post-peak fading marks the forward shock's transition from the dense inner CSM into a more tenuous outer environment. The inferred shock velocities are trans-relativistic, v_sh ~0.1--0.5c. The radio-emitting CSM requires high mass-loading rates, M_dot ~10^{-4}--10^{-3} M_sun yr^{-1}, but modest total CSM masses, M_CSM ~10^{-4}--10^{-2} M_sun.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The circumstellar material follows a broken power-law density profile whose break radius and indices are chosen to match the observed radio light-curve shapes, with radio emission arising solely from forward-shock synchrotron radiation subject only to synchrotron self-absorption and external free-free absorption (abstract, paragraphs describing the model framework).","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"A synchrotron forward-shock model with confined broken-power-law CSM explains FBOT radio diversity via shock transition out of the dense shell, yielding trans-relativistic velocities of 0.1-0.5c and high but brief mass-loss rates of 10^{-4} to 10^{-3} solar masses per year.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Trans-relativistic shocks crossing a confined circumstellar shell explain the radio diversity of fast blue optical transients.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"6f7b6dfdf079f0c3b226cd1d143b8b3b9c396572179affefe9b8a90aa0a1f33e"},"source":{"id":"2605.17280","kind":"arxiv","version":1},"verdict":{"id":"51fe41f2-b100-446c-a526-eafc34448982","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-19T23:16:39.873335Z","strongest_claim":"their radio diversity can be explained by shock propagation through a finite CSM shell. The early radio evolution is regulated by absorption, while the rapid post-peak fading marks the forward shock's transition from the dense inner CSM into a more tenuous outer environment. The inferred shock velocities are trans-relativistic, v_sh ~0.1--0.5c. The radio-emitting CSM requires high mass-loading rates, M_dot ~10^{-4}--10^{-3} M_sun yr^{-1}, but modest total CSM masses, M_CSM ~10^{-4}--10^{-2} M_sun.","one_line_summary":"A synchrotron forward-shock model with confined broken-power-law CSM explains FBOT radio diversity via shock transition out of the dense shell, yielding trans-relativistic velocities of 0.1-0.5c and high but brief mass-loss rates of 10^{-4} to 10^{-3} solar masses per year.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The circumstellar material follows a broken power-law density profile whose break radius and indices are chosen to match the observed radio light-curve shapes, with radio emission arising solely from forward-shock synchrotron radiation subject only to synchrotron self-absorption and external free-free absorption (abstract, paragraphs describing the model framework).","pith_extraction_headline":"Trans-relativistic shocks crossing a confined circumstellar shell explain the radio diversity of fast blue optical transients."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2605.17280/integrity.json","findings":[],"available":true,"detectors_run":[{"name":"doi_title_agreement","ran_at":"2026-05-19T23:31:20.188011Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"doi_compliance","ran_at":"2026-05-19T23:31:00.754123Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"claim_evidence","ran_at":"2026-05-19T22:01:57.827385Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"ai_meta_artifact","ran_at":"2026-05-19T21:33:23.772552Z","status":"skipped","version":"1.0.0","findings_count":0}],"snapshot_sha256":"06787ee8929900405803c1f81dd78151a025bb968e18896d2cb00b7e32a9b78f"},"references":{"count":35,"sample":[{"doi":"","year":2021,"title":"F., Bartel, N., Argo, M., et al","work_id":"87732272-7b4e-4756-b5dd-122d4c0e99d9","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2022,"title":"S., Margutti, R., Matthews, D., et al","work_id":"c3c2a93f-4e84-4d96-8f30-dded8dcb28bc","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":1982,"title":"Chevalier, R. 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