2012A&A...544A...2L

We present a detailed analysis of the X-ray emission of HS 1700+6416, a high-redshift (z=2.7348) luminous quasar classified as a narrow absorption line (NAL) quasar on the basis of its SDSS spectrum. The source has been observed nine times by Chandra and once by XMM-Newton from 2000 to 2007. Long-term variability is clearly detected between the observations in the 2-10keV flux, where it varies by a factor of three (∼3-9x10^–14erg/s/cm2), and in the amount of neutral absorption (N_H<10²²cm^–2 in 2000 and 2002 and N_H=4.4±1.2x10²²cm^–2 in 2007). Most interestingly, one broad absorption feature is clearly detected at 10.3±0.7keV (rest frame) in the 2000 Chandra observation, while two similar features at 8.9±0.4 and at 12.5±0.7keV are visible when the eight contiguous Chandra observations of 2007 are stacked together. In the XMM-Newton observation of 2002, which is strongly affected by background flares, there is a hint of a similar feature at 8.0±0.3keV. We interpreted these features as absorption lines from a high-velocity highly ionized (i.e. Fe XXV, FeXXVI) outflowing gas. In this scenario, the outflow velocities inferred are in the range v=0.12-0.59c. To reproduce the observed features, the gas must have a high column density (N_H>3x10²³cm^–2), high ionization parameter (logξ>3.3erg/s/cm) and a wide range of velocities (ΔV∼10⁴km/s). This absorption line quasar is the fourth high-z quasar that displays X-ray signatures of variable high-velocity outflows, and among these, it is the only one that is not lensed. A rough estimate of the minimum kinetic energy carried by the wind of up to 18% L_bol, based on a biconical geometry of the wind, implies that the amount of energy injected into the outflow environment is large enough to produce effective mechanical feedback.