  Using new XMM-Newton observations we detect hard X-ray time lags in the rapid
variability of the Compton-thin Seyfert 2 galaxy IRAS 18325-5926. The
higher-energy X-ray variations lag behind correlated lower-energy variations by
up to ~3ks and the magnitude of the lag increases clearly with energy
separation between the energy bands. We find that the lag-energy spectrum has a
relatively simple log(E) shape. This is quite different in both shape and
magnitude from the lags predicted by simple reflection models, but very similar
to the hard X-ray lags often seen in black hole X-ray binaries. We apply
several spectral models to the lag-energy spectrum and rule out simple
reflection as an origin for the hard lags. We find that both propagating
fluctuations embedded in the accretion flow and electron scattering from
material embedded in or behind a cold absorbing medium offer equally good fits
to the observed low-frequency hard X-ray lags and are both consistent with the
time-averaged spectrum. Such models will likely look very different outside of
XMM-Newton's observable bandpass, paving the way for future studies with
NuSTAR.
