Short-period variables in the Magellanic Clouds

Abstract

Our knowledge of short-period variables in the Magellanic Clouds remains rather meagre despite the considerable effort that has been put into discovering them. Original failures to detect RR Lyrae variables at the expected magnitude of 17 · 5 led to a temporary belief that perhaps the Clouds contained virtually no Population II. However, the Radcliffe discoveries of RR Lyrae variables in the globular clusters NGC 121 (3), 1466 (44), 1978 (2), and 2257 (17 + 8), put the existence of a Population II component in both Clouds beyond doubt. Moreover, the published light curves and periods of variables in NGC 121 (Thackeray 1958) and NGC 2257 (Alexander 1960) showed the typical characteristics of Bailey types a, b, and c. Thus the comparison, so far as it goes, between the Population II of the Magellanic Clouds and the Galaxy shows no outstanding difference.