{"paper":{"title":"On the mass of the neutron star in Cyg X-2","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.GA","authors_text":"G. Israelian, J. Casares, J.I. Gonzalez Hernandez, R. Rebolo","submitted_at":"2009-10-23T12:27:18Z","abstract_excerpt":"We present new high resolution spectroscopy of the low mass X-ray binary Cyg X-2 which enables us to refine the orbital solution and rotational broadening of the donor star. In contrast with Elebert et al (2009) we find a good agreement with results reported in Casares et al. (1998). We measure $P=9.84450\\pm0.00019$ day, $K_2=86.5\\pm1.2$ km s$^{-1}$ and $V \\sin i=33.7\\pm0.9$ km s$^{-1}$. These values imply $q=M_{2}/M_{1}=0.34 \\pm 0.02$ and $M_{1}=1.71\\pm 0.21$ M$_{\\odot}$ (for $i=62.5 \\pm 4^{\\circ}$). Therefore, the neutron star in Cyg X-2 can be more massive than canonical. We also find no ev"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"0910.4496","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"}