ABSTRACT

Rapid optical variations have been detected for the Seyfert 1 galaxy Akn 120 with time scales shorter than an hour. These variations are the most rapid which have been detected for any Seyfert galaxy, and, for the first time, clearly demonstrate that radio-quiet AGNs exhibit the phenomenon of microvariability. This result suggests that these variations are indepentent of the radio properties of these objects and are thus unlikely to be associated with any disturbance in a relativistic jet.

INTRODUCTION

Akn 120 was first identified as a Seyfert galaxy by Arakelian (1975) in a survey of high surface brightness galaxies. It has long been known to exhibit optical variations with time scales ranging from years to days (Miller 1979). In this paper, we report the first results of a program to determine if radio-quiet AGNs exhibit optical variations on time scales much shorter than a day.

OBSERVATIONS

The high time resolution optical observations of Akn 120 reported here were obtained with the 42-inch telescope at Lowell Observatory equipped with a direct CCD camera and an autoguider. The observations were made through a V filter with an RCA CCD. Repeated exposures of 60 seconds were obtained for the star field containing Akn 120 and several comparison stars. These standard stars, located on the same CCD frame as Akn 120 provide comparison stars for use in the data reduction process. The observations were reduced using the method described in Carini and Miller (1992).