{"paper":{"title":"Formation of black hole stars via star--black hole collisions","arxiv_id":"2608.27596","primary_cat":"astro-ph.HE","submitted_at":"2026-08-27T18:28:50+00:00","version_compiled":"v1"},"notice":"Every quoted sentence is the authors' text from the arXiv listing abstract. Labels and probabilities are the outputs of classifier-1.13.0 on the question bank abstract-p1-20260923, exactly as returned. No sentence in this record was written by a language model.","schema":"pith.compiled-record/v0","status":"compiled","abstract":{"source":"arXiv listing abstract v1","sentences":[{"i":0,"p":1.0,"id":"s0","own":false,"role":"background","text":"In dense stellar environments such as globular clusters and active galactic nucleus (AGN) disks, stellar-mass black holes (sBHs) may frequently collide with massive stars.","hedge":{"p":1.0,"label":"hedged_possibility"},"own_p":0.06,"main_claim_p":0.02,"quantitative":false,"quantitative_p":0.06,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.0,"background":1.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":1,"p":0.7,"id":"s1","own":true,"role":"method","text":"We investigate this process using semi-analytic models, three-dimensional hydrodynamical simulations, and one-dimensional stellar evolution calculations, focusing on collisions between sBHs and a $100\\,M_\\odot$ main-sequence star.","hedge":{"p":0.89,"label":"asserted"},"own_p":0.93,"main_claim_p":0.03,"quantitative":true,"quantitative_p":0.93,"role_probabilities":{"gap":0.0,"method":0.7,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.3,"interpretation":0.0}},{"i":2,"p":1.0,"id":"s2","own":true,"role":"result","text":"We find that gas drag retains the BH within the stellar envelope unless the impact velocity exceeds $\\sim2\\sqrt{G(M_\\star+M_\\bullet)/R_\\star}$.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.9,"main_claim_p":0.07,"quantitative":true,"quantitative_p":0.94,"role_probabilities":{"gap":0.0,"method":0.0,"result":1.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":3,"p":0.97,"id":"s3","own":true,"role":"result","text":"The post-collision outcome depends primarily on the BH-to-star mass ratio.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.8,"main_claim_p":0.18,"quantitative":false,"quantitative_p":0.05,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.97,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.03}},{"i":4,"p":1.0,"id":"s4","own":true,"role":"result","text":"For $M_\\bullet\\gtrsim30\\,M_\\odot$, the retained envelope is either quasi-spherical or disc-like, but remains dynamically unstable because of shock heating.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.94,"main_claim_p":0.09,"quantitative":true,"quantitative_p":0.99,"role_probabilities":{"gap":0.0,"method":0.0,"result":1.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":5,"p":1.0,"id":"s5","own":true,"role":"result","text":"In contrast, for $M_\\bullet\\lesssim10\\,M_\\odot$, the collision forms a ``black hole star'' (BH*): a quasi-hydrostatic, extended stellar envelope surrounding the embedded BH.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.94,"main_claim_p":0.54,"quantitative":true,"quantitative_p":0.95,"role_probabilities":{"gap":0.0,"method":0.0,"result":1.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.0}},{"i":6,"p":0.69,"id":"s6","own":true,"role":"result","text":"These results agree with our analytic prediction that BH* formation necessarily requires $M_\\bullet\\lesssim0.2\\,M_\\star$.","hedge":{"p":0.98,"label":"asserted"},"own_p":0.91,"main_claim_p":0.26,"quantitative":true,"quantitative_p":0.99,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.69,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":0.31}},{"i":7,"p":0.98,"id":"s7","own":true,"role":"result","text":"Follow-up \\texttt{MESA} calculations further show that, for these low-mass BHs, the shock-heated remnant thermally relaxes without triggering runaway expansion.","hedge":{"p":1.0,"label":"asserted"},"own_p":0.96,"main_claim_p":0.07,"quantitative":false,"quantitative_p":0.1,"role_probabilities":{"gap":0.0,"method":0.01,"result":0.98,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.01,"interpretation":0.0}},{"i":8,"p":0.98,"id":"s8","own":true,"role":"interpretation","text":"We discuss several astrophysical implications of BH*s, including their evolution, the possibility of gravitational-wave events from BH binaries assembled within a stellar envelope, and repeated star--sBH collisions as a pathway for rapid BH growth in dense stellar systems.","hedge":{"p":0.49,"label":"asserted"},"own_p":0.52,"main_claim_p":0.08,"quantitative":false,"quantitative_p":0.04,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.01,"contribution":0.01,"interpretation":0.98}},{"i":9,"p":1.0,"id":"s9","own":false,"role":"interpretation","text":"This mechanism may contribute to the formation of massive BHs in high-redshift nuclear star clusters and may be relevant to the origin of the ``little red dots'' discovered by JWST.","hedge":{"p":1.0,"label":"hedged_possibility"},"own_p":0.21,"main_claim_p":0.07,"quantitative":false,"quantitative_p":0.06,"role_probabilities":{"gap":0.0,"method":0.0,"result":0.0,"background":0.0,"limitation":0.0,"future_work":0.0,"contribution":0.0,"interpretation":1.0}}]},"compiled":{"main_claim":{"p":0.89,"text":"In contrast, for $M_\\bullet\\lesssim10\\,M_\\odot$, the collision forms a ``black hole star'' (BH*): a quasi-hydrostatic, extended stellar envelope surrounding the embedded BH.","location":"abstract s5","hedge_strength":{"p":1.0,"label":"asserted"}},"provenance":{"route":{"via":"TypeSafe API","model":"classifier-1.13.0","endpoint":"https://api.typesafe.ai/v1/systemone","provider":"TypeSafe"},"packing":"one request per 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