Periodicity of OJ287 in multisite multifrequency fast photometry?... Now you see it and now you don't

Kidger, Mark; de Diego, Jose A.; Takalo, Leo; Nilsson, Kari; Tornikoski, Merja; Sillanpaa, Aimo; Zerbi, Filippo
Bibliographical reference

American Astronomical Society, 181st AAS Meeting, #11.02; Bulletin of the American Astronomical Society, Vol. 24, p.1134

Advertised on:
12
1992
Number of authors
7
IAC number of authors
2
Citations
1
Refereed citations
1
Description
We report the results of a multisite observing campaign of observations of OJ287 in the visible, near infrared and submillimetric in Winter 1989-90. Simultaneous UBVRIK and white light data were obtained with three telescopes in Tenerife and La Palma on three nights in December-January, supported by follow-up observations in January and March 1990. Each telescope used a different instrument and observing method to take photometry with a resolution from one to a few minutes. The results show widely differing behavior at different frequencies and on different nights, in particular, a number of high amplitude sinusoidal oscillations were seen on December 31 in K and in V, R & I, but were not seen in simultaneous U and B observations. Similar oscillations were also seen in K in mid-January. Periodicity searches of the data show that two characteristic periods are repeated in different data sets, with different instruments, at different frequencies and at different epochs, these being of approximately 23 and 44 minutes period respectively. Confirmatory submillimetric observations at 90GHz carried out in March 1990 also show both of these periods. However, these variations do not show the standard characteristics of a periodicity (e.g.: constant period and amplitude) and are not even always present in the light curve, even in our data. We suggest that talk of "periodic" behavior in this object is specious, at best there may be pseudo-periodicity similar to some classes of semi-regular variable stars. The fact that the light curves in different colors, even of similar wavelength such as B and V show considerable differences, indicates that at least a two-component model and probably one with three or more components is required. The variations show significant time delays of around one third of a period even between V and R.