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We present the analysis of a new broad‐band X‐ray spectrum (0.6–180.0 keV) of the radio‐quiet quasar MR 2251−178 which uses both  Suzaku  and  Swift /Burst Alert Telescope data. In accordance with previous observations, we find that the general continuum can be well described by a power law with Γ= 1.6 and an apparent soft excess below 1 keV. Warm absorption is clearly present, and absorption lines due to the Fe unresolved transition array, Fe L (Fe  xxiii–xxiv ), S  xv  and S  xvi  are detected below 3 keV. At higher energies, Fe K absorption from Fe  xxv–xxvi  is detected and a relatively weak ( EW = 25 +12  −8   eV) narrow Fe Kα emission line is observed ( E = 6.44 ± 0.04 keV) which is well modelled by the presence of a mildly ionized ( ξ≲ 30 ) reflection component with a low reflection fraction ( R  &lt; 0.2). At least five ionized absorption components with  10 20 ≲ N  H ≲ 10 23   cm −2  and 0 ≲ log ξ/erg cm s −1 ≲ 4 are required to achieve an adequate spectral fit. Alternatively, we show that the continuum can also be fit if a Γ∼ 2.0 power law is absorbed by a column of  N  H ∼ 10 23  cm −2  which covers ∼30 per cent of the source flux. Independent of which continuum model is adopted, the Fe L and Fe  xxv  Heα lines are well fit by a single absorber outflowing with  v  out ∼ 0.14 c . Such an outflow/disc‐wind is likely to be substantially clumped ( b ∼ 10 −3 ) in order to not vastly exceed the likely accretion rate of the source.

A broad‐band X‐ray view of the warm absorber in radio‐quiet quasar MR 2251−178