A direct view of the AGN powering IRAS12393+3520

We report the first direct X-ray evidence that an AGN is hidden in the cent er of IRAS 12393+3520. An ASCA observation of this target unveiled a bright (0.5-10 keV luminosity 3.9 x 10(42) erg s(-1)) and variable source, with m inimum observed doubling/halving time scale comprised in the range 30-75 ks . A model composed by a simple power-law, with photon index similar or equa l to 1.8 and an absorption edge, whose threshold energy is consistent with K-shell photoionization of OvII, provides an adequate fit of the spectrum. This suggests that we are observing the emission from the nuclear region th rough a warm absorber of NH a few 10(21) cm(-2). If it has internal dust wi th Galactic gas-to-dust ratio, it could explain the lack of broad H-beta em ission, even in the episodic presence of a broad H-alpha emission line. Opt ical spectra obtained over several years show indeed variations in the stre ngth of this broad H-alpha component. A distribution of dusty, optically th ick matter on spatial scales a few hundreds parsec, which does not intercep t the line of sight towards the nucleus, is probably required to account si multaneously for the relative [OIII] luminosity deficit in comparison to th e X-rays. The high IR to X-ray luminosity ratio is most likely due to inten se star formation in the circumnuclear region. IRAS 12393+3520 might thus e xhibit simultaneously nuclear activity and remarkable star formation.