A broad-band X-ray view of the warm absorber in radio-quiet quasar MR2251-178

Journal article

We present the analysis of a new broad-band X-ray spectrum (0.6-180.0keV) of the radio-quiet quasar MR2251-178 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 1keV. Warm absorption is clearly present, and absorption lines due to the Feunresolved transition array, FeL (Fexxiii-xxiv), Sxv and Sxvi are detected below 3keV. At higher energies, FeK absorption from Fexxv-xxvi is detected and a relatively weak (EW = 25+12-8eV) narrow FeKα emission line is observed (E= 6.44 ± 0.04keV) which is well modelled by the presence of a mildly ionized (ξ≲ 30) reflection component with a low reflection fraction (R < 0.2). At least five ionized absorption components with 1020≲NH≲ 1023 cm-2 and 0 ≲ logξ/ergcms-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 NH∼ 1023cm-2 which covers ∼30 per cent of the source flux. Independent of which continuum model is adopted, the FeL and Fexxv Heα lines are well fit by a single absorber outflowing with vout∼ 0.14c. 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. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Authors: Gofford, J; Reeves, J; Turner, T; Tombesi, F; Braito, V

• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 414
• Issue: 4
• Pages: 3307-3321
• Publication date: 2011-07-01
• DOI: 10.1111/j.1365-2966.2011.18634.x
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: X-rays: galaxies; Galaxies: active; Galaxies: individual: MR2251-178