Second Parameter Effects in and between M3 and Palomar 3

Abstract

We study the globular clusters M3 and Palomar 3 as a "second parameter (2ndP) pair," showing that: i) M3 has a surprisingly strong *internal* 2ndP; ii) The dispersion in mass on the Pal 3 horizontal branch (HB) is intrinsically very small, leading to the most apparent differences in HB morphology between M3 and Pal 3; iii) Ignoring the difference in HB mass dispersion between M3 and Pal 3, their relative HB types can be accounted for by a fairly small difference in age, of order 0.5-1 Gyr.