{"paper":{"title":"X-shooter observations of main sequence stars in the globular cluster NGC 2808: first chemical tagging of a He-normal and a He-rich dwarf","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.GA","authors_text":"(2) INAF-Oss. Astr. Padova, (3) Univ. Padova, (4) INAF-Oss. Astr. Collurania, (5) Dept. Astronomy, A. Bragaglia (1), A. Milone (3), C. Sneden (5), E. Carretta (1), G. Piotto (3), L.R. Bedin (6) ((1) INAF-Oss. Astr. Bologna, McDonald Obs. (6) STScI), R.G. Gratton (2), S. Cassisi (4), S. Lucatello (2), V. D'Orazi (2)","submitted_at":"2010-07-29T19:14:32Z","abstract_excerpt":"We present the first chemical composition study of two unevolved stars in the globular cluster NGC 2808, obtained with the spectrograph X-shooter@VLT. NGC 2808 shows three discrete, well separated main sequences. The most accepted explanation for this phenomenon is that their stars have different helium contents. We observed one star on the bluest main sequence, (bMS, claimed to have high helium content, Y~0.4), and one on the reddest main sequence (rMS, consistent with a canonical helium content, Y=0.245). We analyzed features of NH, CH, Na, Mg, Al, and Fe. While Fe, Ca, and other elements ha"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1007.5299","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"}