Detection of Absorption Features in the X-ray Spectrum of the Narrow-line Quasar Pg 1404+226: Possible Evidence for Accretion Disc Winds

We present the results of an analysis of data from XMM-Newton and CHANDRA observations of the high luminosity narrow-line quasar PG 1404+226. We confirm a strong soft X-ray excess in the X-ray spectrum and we find rapid variability (a factor of two in about 5000 s) in both XMMNewton and CHANDRA data. When the X-ray spectrum is fit with a two component model which includes a power-law (Γ ∼ 1.6) and a blackbody component (kT ∼ 114 eV), we find that low energy absorption lines are required to fit the data. If we interpret these lines as due to highly ionized species of heavy elements in an outflowing accretion disc wind, an outflow velocity of ∼ 23000 km s could be derived. One interesting feature of the present observation is the possible detection of variability in the absorption features: the absorption lines are visible only when the source is bright. From the upper limits to the equivalent widths of the absorption lines during the low flux states and also from the model independent pulse height ratios, we argue that the strength of absorption is lower during the low flux states. This gives a constraint for the physical size of the absorbing medium to be within 100 Schwartzschild radius of the putative supermassive black hole. We also find a marginal evidence for a correlation between the strength of the absorption line and the X-ray luminosity. Subject headings: galaxies: active – galaxies: individual: PG 1404+226 – galaxies: QSO – X-rays: galaxies