Timescales of the Optical Variability of the BL Lacertae Galaxy PKS 2201+044

Summary

Introduction

BL Lacertae objects have been characterized by rapid and large amplitude optical variability, by a highly variable and polarized optical continuum which is featureless, or one in which any discrete features are found only in low contrast to the continuum. In the present investigation, the BL Lacertae object with the most significant galaxy component detected to date, PKS 2201+044, has been studied. The purpose of the investigation is to present the results of eighteen years of photometric monitoring of this BL Lacertae galaxy.

Observations

The observations of PKS 2201+044 were obtained with the 0.9 m and 1.3 m telescopes at KPNO and the 42-in. telescope at Lowell Observatory Observatory, all of which were equipped with a direct CCD camera. The details of the observations, data reduction, and analysis are the same as those described by Noble and Miller (this volume).

Discussion

Multiple aperture photoelectric and CCD observations were obtained on several nights. These were used to derive an aperture correction using the method outlined by Sandage (1973), which was applied to all the observations to derive V^*, the V-magnitude in a standard aperture of 15.42 arcseconds. Over the eighteen-year period of the observations, we see a general increase in brightness reaching a maximum in 1987, followed by a decline until the fall, 1991. A major exception to this is the observation of 1981 June 7 when the object was observed at V = 16.31. PKS 2201+044 was also observed at a similar brightness of V = 16.43 on 1987 November 9.