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Observational studies of Cepheids. II - BVRI photometry of 112 Cepheids
Over 4000 differentially determined photoelectric BVRI observations andthe resulting light curves are presented for 112 Cepheids accessiblefrom Northern Hemisphere observatories. The internal precision of thesedata is better than + or - 0.01 mag, and the accuracy of transformationto the Johnson BVRI system is nearly as good.
| TU Cassiopeiae periods and amplitudes
Light-curve observations of the double-mode Cepheid TU Cas obtained by10 different groups of observers on several photometric systems over atime span of 67 years have been carefully studied to determine thefundamental and first-overtone periods and their amplitudes on the Vmagnitude scale. The presence of a second-overtone radial pulsation isdiscussed, and it is concluded that a previous detection of this modewas spurious because of the lack of a proper zero-point correction fortwo groups of observations. It is possible that the amplitude of one ofthe two modes varies during the entire observing period, with thefundamental-mode amplitude constant at 0.69 plus or minus 0.03 and theovertone amplitude decreasing from 0.4 to 0.25 mag. If this Cepheiddisplays the two pulsation modes because it is mode switching, thisswitching time scale may be less than a few hundred years.
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