The broad iron K emission line in the Seyfert 2 galaxy IRAS 18325-5926

We report the detection of a very broad iron K alpha emission line in the ASCA X-ray spectrum of the Seyfert 2 galaxy IRAS 18325 - 5926. The line is strong, with an equivalent width EW = 500-800 eV, and its profile is peaked at 6.9 keV and skewed down to 4 keV. The energy of the blue peak of the line is significantly higher than the rest-energy of 6.4 keV seen in many active galaxies, which is expected from an iron K alpha line arising in cold matter. If the breadth and shift of the line energy are caused by Doppler and relativistic effects in a cold accretion disc about a black hole, then the disc has an intermediate inclination, i = 40 degrees-50 degrees. A plausible interpretation for the large equivalent width is a supersolar abundance of iron; this also accounts for the lack of a significant reflection hump. The line profile can also be explained by emission from highly ionized matter very close to the central object. However, the lack of a deep iron K absorption edge in the Ginga spectrum is inconsistent with this interpretation. We verify that fast X-ray variability on a time-scale of 10(4) s is common in this object, using ASCA and ROSAT observations which are partially simultaneous. A study of spectral variability using combined ASCA and ROSAT PSPC data reveals that the X-ray flux change occurred mainly above 1 keV, and suggests a stable, or at least less-variable, component below 1 keV. It should lie outside the nuclear obscuration region.