Do the Pulsation Properties of Red Giants Vary around their Long Secondary Period Cycle?

TL;DR

This study investigates whether the pulsation periods and amplitudes of certain red giants change during their long secondary period cycles, finding no significant variations and suggesting the LSPs do not alter the stars' observable physical properties.

Contribution

It provides observational evidence that the pulsation properties of red giants remain stable across their long secondary period cycles, challenging some theories about LSP effects.

Findings

No significant changes in pulsation period during LSP cycles

No significant changes in pulsation amplitude during LSP cycles

LSPs do not significantly affect the stars' visible physical properties

Abstract

We have used visual and Johnson V observations from the American Association of Variable Star Observers (AAVSO) International Database, and the AAVSO VSTAR time-series package, and (O-C) analysis to investigate possible changes in the pulsation period and amplitude of the pulsating red giants U Del, EU Del, X Her, and Y Lyn around the cycle of their long secondary periods (LSPs). We find no such changes in period or amplitude. This suggests (weakly) that the process -- whatever it is -- that causes the LSPs does not significantly change the physical properties of the visible hemisphere of the stars as the LSP cycle proceeds.