{"work":{"id":"acd32913-a25f-473c-ab82-6608f54b5c6a","openalex_id":null,"doi":null,"arxiv_id":"2508.21748","raw_key":null,"title":"A direct black hole mass measurement in a Little Red Dot at the Epoch of Reionization","authors":null,"authors_text":"Juodžbalis, I","year":2025,"venue":"astro-ph.GA","abstract":"Recent discoveries of faint active galactic nuclei (AGN) at the redshift frontier have revealed a plethora of broad \\Halpha emitters with optically red continua, named Little Red Dots (LRDs), which comprise 15-30\\% of the high redshift broad line AGN population. Due to their peculiar spectral properties and X-ray weakness, modeling LRDs with standard AGN templates has proven challenging. In particular, the validity of single-epoch virial mass estimates in determining the black hole (BH) masses of LRDs has been called into question, with some models claiming that masses might be overestimated by up to 2 orders of magnitude, and other models claiming that LRDs may be entirely stellar in nature. We report the direct, dynamical BH mass measurement in a strongly lensed LRD at $z = 7.04$. The combination of lensing with deep spectroscopic data reveals a rotation curve that is inconsistent with a nuclear star cluster, yet can be well explained by Keplerian rotation around a point mass of 50 million Solar masses, consistent with virial BH mass estimates from the Balmer lines. The Keplerian rotation leaves little room for any stellar component in a host galaxy, as we conservatively infer $M_{\\rm BH}/M_{*}>2$. Such a ''naked'' black hole, together with its near-pristine environment, indicates that this LRD is a massive black hole seed caught in its earliest accretion phase.","external_url":"https://arxiv.org/abs/2508.21748","cited_by_count":null,"metadata_source":"pith","metadata_fetched_at":"2026-07-01T14:45:50.263803+00:00","pith_arxiv_id":"2508.21748","created_at":"2026-05-09T23:24:43.029746+00:00","updated_at":"2026-07-01T14:45:50.263803+00:00","title_quality_ok":true,"display_title":"arXiv e-prints , keywords =","render_title":"arXiv e-prints , keywords ="},"hub":{"state":{"work_id":"acd32913-a25f-473c-ab82-6608f54b5c6a","tier":"hub","tier_reason":"10+ Pith inbound or 1,000+ external citations","pith_inbound_count":13,"external_cited_by_count":null,"distinct_field_count":3,"first_pith_cited_at":"2026-01-05T18:12:33+00:00","last_pith_cited_at":"2026-06-30T11:29:36+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":"2026-07-02T02:52:14.626777+00:00","tier_text":"hub"},"tier":"hub","role_counts":[{"context_role":"background","n":1}],"polarity_counts":[{"context_polarity":"background","n":1}],"runs":{},"summary":{},"graph":{},"authors":[]}}