We present the 0.1–200 keV BeppoSAX spectrum of MR 2251-178 observed at two epochs in 1998 separated by 5 months .
Both epochs show identical spectral shape and X-ray flux .
Analysis of the combined spectra allow us to confirm the presence of the ionized Fe K \alpha line detected by ASCA and to test the presence of reflection from ionized material .
The best self-consistent spectral fit is obtained when including a contribution from a mildly ionized reflector ( \xi _ { 0.01 - 100 } \sim 1625 erg cm s ^ { -1 } , i.e .
U _ { 0.1 - 10 } \sim 0.14 ) with a reflection fraction R _ { ion } \sim 0.11 .
An exponential cut-off to the direct power-law continuum is then required at { E } \sim 100 keV .
The low energy spectrum is absorbed by ionized matter with a column density N _ { W } = ( 8.1 _ { -1.2 } ^ { +2.1 } ) \times 10 ^ { 21 } cm ^ { -2 } and an X-ray ionization parameter U _ { 0.1 - 10 } = 0.06 \pm 0.01 .
The warm absorber column is slightly lower than that measured with ASCA .
This change could be caused by bulk motion .
The BeppoSAX absorber ionization parameter globally agrees with the “ U versus Flux ” correlation found for MR 2251-178 with EXOSAT , Ginga and ASCA .
This suggests that the absorber is in a state of instantaneous ionization equilibrium .