查看“Oosterhoff dichotomy”的源代码

One of the open problems concerning RRLs is the Oosterhoff dichotomy, namely the sub�division of GGCs into two distinct groups according to the av�erage period < Pab > of their fundamental mode RRL variables
(RRab, Oosterhoff 1939). In particular, in some GGCs contain�ing RRLs, < Pab > is about 0.55 days while in others, it is close
to 0.65 days, with a period gap between these two groups, named Oosterhoff I (OoI) and Oosterhoff II (OoII), respectively.