Monday, January 14, 2013

1301.2575 (Andrea Kunder et al.)

Theoretical Modeling of the RR Lyrae Variables in NGC 1851    [PDF]

Andrea Kunder, Maurizio Salaris, Santi Cassisi, Roberto de Propris, Alistair Walker, Peter B. Stetson, Marcio Catelan, Pia Amigo
The 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 (Y~0.248-0.270) 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 (Y~0.270-0.280) have longer periods at a given amplitude, as is seen with Oosterhoff II (OoII) RR Lyrae variables, whereas the RR Lyrae variables with Y~0.248-0.270 have shorter periods, exhibiting properties of Oosterhoff I (OoI) variables.
View original:

No comments:

Post a Comment