Evidence of rapid optical variability in selected narrow-line Seyfert 1 galaxies

We present the first results of a search for the presence of rapid optical variability in a sample of five Narrow-Line Seyfert 1 galaxies. We find cle ar evidence of rapid variability for IRAS 13224-3809 with variations occurr ing on time scales of an hour. However, the results are less conclusive for the other four sources in our sample, Markarian 766, PG 1244+026, PG 1404226 and Arakelian 564. While there are several instances among these latter objects where there is a hint that variability may be present, IRAS 13224- 3809 provides the only conclusive evidence of rapid optical variability det ected to date. (C) 2000 Elsevier Science B.V. All rights reserved.