Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Periodic optical variability of AGN   Here we present the evidence for periodicity of an optical emission detected
in several AGN. Significant periodicity is found in light curves and radial
velocity curves. We discuss possible mechanisms that could produce such
periodic variability and their implications. The results are consistent with
possible detection of the orbital motion in proximity of the AGN central
supermassive black holes.

1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an