{"paper":{"title":"Optical studies of the ultraluminous X-ray source NGC1313 X-2","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"CfA), Jifeng Liu (Harvard-Smithsonian, Joel Bregman (U. of Michigan), Jon Miller (U. of Michigan), Philip Kaaret (U. of Iowa)","submitted_at":"2007-03-27T19:56:18Z","abstract_excerpt":"NGC1313 X-2 was among the first ultraluminous X-ray sources discovered, and has been a frequent target of X-ray and optical observations. Using the HST/ACS multi-band observations, this source is identified with a unique counterpart within an error circle of $0\\farcs2$. The counterpart is a blue star on the edge of a young cluster of $\\le10^7$ years amid a dominant old stellar population. Its spectral energy distribution is consistent with that for a Z=0.004 star with 8.5 $M_\\odot$ about $5\\times10^6$ years old, or for an O7 V star at solar metallicity. The counterpart exhibited significant va"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/0703697","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}