Long-term photoelectric V photometry of 13 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 (APT) and from the photoelectric photometry program of the American Association of Variable Star Observers has been merged to form data sets that are significantly longer and denser than the subsets, and have been analyzed using Fourier and self-correlation techniques. Improved values of the pulsation periods, and especially of the enigmatic long secondary periods (LSPs), have been determined. Most of the stars also show very slow, small variations in amplitude and mean magnitude on timescales of thousands of days. The amplitude variability has also been studied, using both least-squares and wavelet analysis; the dominant amplitude variability is on a timescale of years. The period of EU Del shows neither long-term secular changes nor random cycle-to-cycle fluctuations. APT VRI photometry for 16 stars has been analyzed: for both the pulsation periods and for the long secondary periods (with one notable exception—EG And), the amplitude decreases with increasing wavelength.
John R. Percy et al 2008 PASP 120 523
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