Reexamining the beat Cepheid TU CAS - No second overtone, no mode switching
Jaymie M. Matthews, W. Gieren, J. D. Fernie, N. Dinshaw · The Astronomical Journal · 1992
Simultaneous photometry and radial-velocity measurements of the double-mode Cepheid TU Cas were obtained in 1987, to check on the mode behavior of this star after a decade-long gap in the observing record. Least-squares fits of these data are performed to isolate the primary (2.14 d) and secondary (1.52 d) variations. The residuals of the present solution rule out the existence of any tertiary mode with V and velocity amplitudes greater than 0.004 mag and 0.7 km/s, respectively, contradicting Faulkner's (1977) report of such a mode with amplitude 0.05 mag. Nor is a significant change detected in the relative amplitudes of the modes compared to previous data, cited as evidence for mode switching in this star by earlier investigators.