\xmmuj is an X-ray source discovered serendipitously by XMM-Newton which was found to be spatially coincident with a pair of galaxies , including a Seyfert 2 galaxy , but presented in 2003 a very sharp persistent flux drop of a factor 6.5 within 1 h. From the analysis of a set of 29 Swift observations conducted from the 6 February to the 23 May 2008 , we discovered twin-peak quasi-periodic oscillations ( QPOs ) with periods of 23.82 \pm 0.07 h and 71.44 \pm 0.57 h. Using a Chandra observation of 2008 , we evaluate more accurately the position of the X-ray source and show that the new source coordinates coincide with the position of the Seyfert 2 galaxy .
We provide a detailed spectral energy distribution of the AGN counterpart using multi-wavelength observations .
The AGN is radio-loud and the broadband SED modelling indicates a black hole with a mass of 9.8 \times 10 ^ { 6 } M _ { \odot } , that accretes at an Eddington ratio of 0.047 .
QPOs for active galaxies have been reported so far in only few cases , the most reliable one being from RE J1034+396 for which a 1 h periodicity has been discovered analysing a ~ { } 91 ks XMM-Newton observation .
Twin peak QPOs with an observed frequency ratio of 3:1 have not been reported so far for any AGN .
From resonance models of the epicyclic frequencies we evaluate the different possible mass-spin relations .
It ’ s still not clear what could have been the origin of the high flux and sharp drop only observed in 2003 .