Heavenly Harmony: Red Giants Pulsating in Many Modes (Abstract)

Volume 31 number 2 (2003)

John R. Percy

Akos G. Bakos

Gurtina Besla

Gregory W. Henry

Vince Velocci

Abstract

(Abstract only) We have analyzed the complex variability of five small-amplitude pulsating red giants — RZ Ari, V523 Mon, BC CMi, UX Lyn, FS Com — using a 5000-day database of V photometry from a robotic telescope. For each of these stars, two or three periods recur in each season, and are present in separate halves of the dataset. The periods and their ratios are consistent with low-order radial pulsation modes; the stars are pulsating in multiple overtones, or harmonics. The amplitudes of the modes rise and fall significantly on time scales of 2000 to 3500 days. In UX Lyn and FS Com, there are long secondary periods which add a bass drone to the wavering chord of the radial modes. Even with all these periods accounted for, there are small residuals, which suggest that the celestial harmony is even more complex than we might think.