Long-Term Photometric Variability of 13 Bright Pulsating Red Giants (Abstract)

Volume 36 number 1 (2008)

John R. Percy

Cristina O. Nasui

Gregory W. Henry

Abstract

(Abstract only) Red giant stars cooler than 4000 K are unstable to pulsation; pulsating red giants make up ten per cent of all the bright stars. We have merged long-term (typically twenty years or more) photoelectric V photometry of thirteen bright pulsating red giants (TV Psc, EG And, RZ Ari, η Gem, V614 Mon, RS Cnc, VY UMa, FS Com, SW Vir, R Lyr, EU Del, V1070 Cyg, and W Cyg), from a robotic telescope, and from the photoelectric photometry program of the American Association of Variable Star Observers (AAVSO), and analyzed each merged dataset using Fourier and self-correlation techniques. Several of the stars show two or more pulsation periods, and we have derived improved values of these. We have also derived improved values of the enigmatic long secondary periods which are present in several of the stars, and whose cause is unknown. Most of the stars also show very slow, small variations in amplitude and mean magnitude on time scales of thousands of days, whose cause is also unknown. We will also discuss, briefly, the nature and value of this project as an undergraduate research experience.