(IAU, European Regional Astronomy Meeting, 11th, La Laguna, Spain, July 3-8, 1989) Astrophysics and Space Science (ISSN 0004-640X), vol. 171, no. 1-2, Sept. 1990, p. 97-104.
de Diego, Jose Antonio; Kidger, Mark
A periodic signal of high nominal significance (99.95 percent) is found in the light curve of OJ 287 in observations taken with the Prime Focus Camera Unit on the 2.5 m Isaac Newton Telescope on two nights in March-April 1987. No such periodicity is seen in the light curve of the simultaneously observed reference star. A null test involving observations taken with an identical method on the same telescope in January 1989 suggests strongly that alternative explanations such as instrumental stability or observational effects are not the cause. On the first night, periodicity of different amplitudes is seen in B, V, R, and I. On the second night of monitoring, the periodicity was still present in Gunn-Z but, had disappeared in B. This provides strong evidence that such periodicities are ephemeral phenomena.