Some Thoughts About the Blazhko Effect for RR Lyrae Variable Pulsations

Abstract

The amplitude variations in a few RR Lyrae stars seem possible as the beating of the main pulsation mode (a radial variation) and a nonradial l = 1 mode of high radial order with a period very close to the main mode. My report of this beating has been given at the Victoria (1992) and Santa Fe (2009) stellar pulsation conferences, with the first of these suggesting the radial (l = 0) and the l = 1 g4 modes occurring and the radial and the g12 modes not actually predicted to be both self excited. Recent studies show that a nonradial mode might depend on the interior structure, both based on the material opacity an its dependence on temperature and density. Current linear theory for pulsation calculations using my much improved pulsation code show that two beating modes (one radial and another nonradial) may exist for an explanation of those few pulsating RR Lyrae, amplitude varying variable stars.