We have analyzed the timing properties of the Narrow-line Seyfert 1 galaxy Mrk 766 observed with XMM-Newton during the PV phase .
The source intensity changes by a factor of 1.3 over the 29,000 second observation .
If the soft excess is modeled by a black body component , as indicated by the EPIC pn data , the luminosity of the black body component scales with its temperature according to L \sim T ^ { 4 } .
This requires a lower limit ’ black body size ‘ of about 1.3 \cdot 10 ^ { 25 } cm ^ { 2 } .
In addition , we report the detection of a strong periodic signal with 2.4 \cdot 10 ^ { -4 } Hz .
Simulations of light curves with the observed time sequence and phase randomized for a red noise spectrum clearly indicate that the periodicity peak is intrinsic to the distant AGN .
Furthermore , its existence is confirmed by the EPIC MOS and RGS data .
The spectral fitting results show that the black body temperature and the absorption by neutral hydrogen remain constant during the periodic oscillations .
This observational fact tends to rule out models in which the intensity changes are due to hot spots orbiting the central black hole .
Precession according to the Bardeen-Petterson effect or instabilities in the inner accretion disk may provide explanations for the periodic signal .