RW per: Nodal motion changes its amplitude by 1.4 mag

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RW Per was found to have large secular changes in its eclipse amplitude. In blue light for example, the amplitude was 3.2 mag in the early 1900's, 2.2 mag in the late 1960's, and 1.75 mag in 1990. Through-out this time, the brightness at maximum was constant in all colors. We show that the only possible explanation is nodal motion, where the inclination varies with a period of roughly 105 yr. The nodal motion is caused by a third star, for which the light curve, the colors, and the O - C curve already provides evidence. Thus, RW Per is only the fourth known star with large changes of eclipse amplitude and is only the second example of nodal motion.

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Astronomical Journal

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