2000A&A...355..113G

We report the first direct X-ray evidence that an AGN is hidden in the center of IRAS 12393+3520. An ASCA observation of this target unveiled a bright (0.5-10keV luminosity 3.9x10⁴²erg/s) and variable source, with minimum observed doubling/halving time scale comprised in the range 30-75ks. A model composed by a simple power-law, with photon index ≃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 through a warm absorber of N_H≃ a few 10²¹cm^–2. If it has internal dust with Galactic gas-to-dust ratio, it could explain the lack of broad H_β emission, even in the episodic presence of a broad H_α emission line. Optical spectra obtained over several years show indeed variations in the strength of this broad H_α component. A distribution of dusty, optically thick matter on spatial scales a few hundreds parsec, which does not intercept the line of sight towards the nucleus, is probably required to account simultaneously for the relative [OIII] luminosity deficit in comparison to the X-rays. The high IR to X-ray luminosity ratio is most likely due to intense star formation in the circumnuclear region. IRAS 12393+3520 might thus exhibit simultaneously nuclear activity and remarkable star formation.