SIMBAD references

We present Rossi X-ray Timing Explorer monitoring observations of the type 2 Seyfert galaxy Markarian 3 spanning a 200-d period during which time the source flux varied by a factor of ∼2 in the 4-20keV bandpass. In broad agreement with earlier Ginga results, the average spectrum can be represented in terms of a simple spectral model consisting of a very hard power-law continuum (Γ~1.1) modified below ∼6keV by a high absorbing column (N_H∼6x10²³cm^–2) together with a high equivalent width FeK emission feature at 6.4keV. The abnormally flat spectral index is probably the signature of a strong reflection component and we consider two models incorporating such emission. In the first the reflected signal suffers the same absorption as the intrinsic continuum, whereas in the second the reflection is treated as an unabsorbed spectral component. In the former case, we require a very strong reflection signal (R≲3) in order to match the data; in addition variability of both the intrinsic power-law and the reflection components is required. The unabsorbed reflection model requires a somewhat higher line-of-sight column density to the nuclear source (∼10²⁴cm^–2), but in this case the reflected signal remains constant whilst the level of the intrinsic continuum varies. The latter description is consistent with the reflection originating from the illuminated far inner wall of a molecular torus, the near side of which screens our direct view of the central continuum source.