Periodic Variability on Time-scales of Decades to Centuries in Magnetic Ap Stars: Challenges and Strategies

Abstract

Recent studies have revealed the existence of a significant population of Ap stars with extremely long rotation periods, and the frequent occurrence of Ap stars in wide binaries. Those results represent new constraints on the understanding of the origin and evolution of Ap stars, and (by extension) of all upper-main-sequence stars. Current knowledge of Ap stars with the longest rotation and orbital periods remains incomplete, on the one hand because in many cases the periods of interest are longer than the time-spans over which relevant observations have been obtained, and on the other hand because some important subsets of Ap stars have been omitted from the studies that have been carried out until now. Additional observations over time-scales of decades to centuries are needed to complement the current incomplete picture. Securing them with the required accuracy and time coverage, and ensuring that their full exploitation will ultimately be possible, represents a unique challenge in time-domain astronomy.

Photometric variability of the LAMOST sample of magnetic chemically peculiar stars as seen by TESS

“…Several stars are clearly variable but have periods too long to be resolved with the rather short time baseline of the employed TESS data. That is expected, as ACV variables can have periods of up to decades or even longer (Mathys 2019;Mathys et al 2019Mathys et al , 2020aMathys et al ,b, 2022. These objects are identified by the remark 'long-period var.'…”