{"work":{"id":"54fcd5b6-fa18-473e-bab8-5964ede247b6","openalex_id":"https://openalex.org/W6891887076","doi":"10.48550/arxiv.2404.04248","arxiv_id":"2404.04248","raw_key":null,"title":"Observation of Gravitational Waves from the Coalescence of a $2.5\\text{-}4.5~M_\\odot$ Compact Object and a Neutron Star","authors":null,"authors_text":"A","year":2024,"venue":"astro-ph.HE","abstract":"We report the observation of a coalescing compact binary with component masses $2.5\\text{-}4.5~M_\\odot$ and $1.2\\text{-}2.0~M_\\odot$ (all measurements quoted at the 90% credible level). The gravitational-wave signal GW230529_181500 was observed during the fourth observing run of the LIGO-Virgo-KAGRA detector network on 2023 May 29 by the LIGO Livingston Observatory. The primary component of the source has a mass less than $5~M_\\odot$ at 99% credibility. We cannot definitively determine from gravitational-wave data alone whether either component of the source is a neutron star or a black hole. However, given existing estimates of the maximum neutron star mass, we find the most probable interpretation of the source to be the coalescence of a neutron star with a black hole that has a mass between the most massive neutron stars and the least massive black holes observed in the Galaxy. We provisionally estimate a merger rate density of $55^{+127}_{-47}~\\text{Gpc}^{-3}\\,\\text{yr}^{-1}$ for compact binary coalescences with properties similar to the source of GW230529_181500; assuming that the source is a neutron star-black hole merger, GW230529_181500-like sources constitute about 60% of the total merger rate inferred for neutron star-black hole coalescences. The discovery of this system implies an increase in the expected rate of neutron star-black hole mergers with electromagnetic counterparts and provides further evidence for compact objects existing within the purported lower mass gap.","external_url":"https://arxiv.org/abs/2404.04248","cited_by_count":4,"metadata_source":"pith","metadata_fetched_at":"2026-08-05T02:28:24.338817+00:00","pith_arxiv_id":"2404.04248","created_at":"2026-05-08T23:14:24.127652+00:00","updated_at":"2026-08-05T02:28:24.338817+00:00","title_quality_ok":true,"display_title":"Ob- servation of Gravitational Waves from the Coalescence of a 2.5 − 4.5 M⊙ Compact Object and a Neutron Star","render_title":"Ob- servation of Gravitational Waves from the Coalescence of a 2.5 − 4.5 M⊙ Compact Object and a Neutron Star"},"hub":{"state":{"work_id":"54fcd5b6-fa18-473e-bab8-5964ede247b6","tier":"hub","tier_reason":"10+ Pith inbound or 1,000+ external citations","pith_inbound_count":19,"external_cited_by_count":4,"distinct_field_count":5,"first_pith_cited_at":"2024-06-05T18:30:33+00:00","last_pith_cited_at":"2026-07-08T17:23:41+00:00","author_build_status":"not_needed","summary_status":"needed","contexts_status":"needed","graph_status":"needed","ask_index_status":"not_needed","reader_status":"not_needed","recognition_status":"not_needed","updated_at":"2026-08-21T17:49:41.891802+00:00","tier_text":"hub"},"tier":"hub","role_counts":[{"context_role":"background","n":4},{"context_role":"method","n":1}],"polarity_counts":[{"context_polarity":"background","n":4},{"context_polarity":"use_method","n":1}],"runs":{},"summary":{},"graph":{},"authors":[]}}