Kunder, A.A.KunderSalaris, M.M.SalarisCASSISI, SantiSantiCASSISIde Propris, R.R.de ProprisWalker, A.A.WalkerStetson, P. B.P. B.StetsonCatelan, M.M.CatelanAmigo, P.P.Amigo2020-04-032020-04-0320150037-8720http://hdl.handle.net/20.500.12386/23818The RR Lyrae instability strip (IS) in NGC 1851 is investigated, and a model is presented which reproduces the pulsational properties of the RR Lyrae population. In our model, a stellar component within the IS that displays minor helium variations (Ỹ0.248-0.270) is able to reproduce the observed periods and amplitudes of the RR Lyrae variables, as well as the frequency of fundamental and first-overtone RR Lyrae variables. The RR Lyrae variables therefore may belong to an He-enriched second generation of stars. The RR Lyrae variables with a slightly enhanced helium (Ỹ0.270-0.280) have longer periods at a given amplitude, as is seen with Oosterhoff II (OoII) RR Lyrae variables, whereas the RR Lyrae variables with Ỹ0.248-0.270 have shorter periods, exhibiting properties of Oosterhoff I (OoI) variables.STAMPAenArticlehttp://sait.oat.ts.astro.it/MSAIt860215/index.html2015MmSAI..86..199KFIS/05 - ASTRONOMIA E ASTROFISICA