Spectroscopic analysis of the two subgiant branches of the globular cluster NGC 1851 R. G. Gratton, S. Villanova, S. Lucatello, A. Sollima, D. Geisler, E. Carretta, S. Cassisi and A. Bragaglia A&A, 544 (2012) A12 Published online: 19 July 2012 DOI: 10.1051/0004-6361/201219276