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J.R. Percy, J.B. Wilson (U. Toronto), G.W. Henry (Tennessee State U.)
We report up to 5000 days of VRI photometry, from a robotic photometric telescope, of 37 pulsating red giants, namely: TV Psc, EG And, Z Psc, RZ And, 4 Ori, RX Lep, \eta Gem, \mu Gem, UW Lyn, \psi1 Aur, V523 Mon, V614 Mon, HD 52690, Y Lyn, BC CMi, X Cnc, UX Lyn, RS Cnc, VY UMa, ST UMa, TU CVn, FS Com, 35 Com, SW Vir, 30 Her, \alpha1 Her, V642 Her, R Lyr, HD 174621, V450 Aql, V1293 Aql, \delta Sge, EU Del, V1070 Cyg, W Cyg, \mu Cep, and \nu Cep. V, R, and I variations are generally in phase. The length and density of the data enable us to look for variations on time scales ranging from days to years. We use both power-spectrum (Fourier) analysis, and autocorrelation analysis, as well as light-curve analysis; these three approaches are complementary. The variations range from regular to irregular but, in most of the stars, we find a period in the range of 20 to 200 days which is probably due to low-order radial pulsation. In many of the stars, we also find a period which is an order of magnitude longer. It may be due to rotation, or it may be due to a new kind of convectively-induced oscillatory thermal mode, recently proposed by Peter Wood.
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Supported by NASA, NSF, and NSERC Canada.