The Na-O anticorrelation in horizontal branch stars - V. NGC 6723 R. G. Gratton, S. Lucatello, A. Sollima, E. Carretta, A. Bragaglia, Y. Momany, V. D’Orazi, M. Salaris, S. Cassisi and P. B. Stetson A&A, 573 (2015) A92 Published online: 23 December 2014 DOI: 10.1051/0004-6361/201424393