Chandra X-ray observations of the quadruply lensed quasar RX J0911.4+0551

We present results from X-ray observations of the quadruply lensed quasar R X J0911.4+0551 using data obtained with the Advanced CCD Imaging Spectromet er on board the Chandra X-Ray Observatory. The 29 ks observation detects a total of similar to 404 X-ray photons (0.3 to 7.0 keV) from the four images of the lensed quasar. Deconvolution of the aspect-corrected data resolves all four lensed images, with relative positions in good agreement with opti cal measurements. When compared with contemporaneous optical data, one of t he lensed images (component A3) is dimmer by a factor of similar to6 in X-r ays with respect to the two brighter images (components A1 and A2). Spectra l fitting for the combined images shows significant intrinsic absorption in the soft (0.2-2.4 keV) energy band, consistent with the mini- broad absorp tion line (BAL) nature of this quasar, while a comparison with ROSAT Positi on Sensitive Proportional Counter observations from 1990 shows a drop of si milar to6.5 in the total soft bandpass flux. The observations also detect s imilar to 157 X-ray photons arising from extended emission of the nearby cl uster (peaked similar to 42" southwest of RX J0911.4+0551) responsible for the large external shear present in the system. The Chandra observation rev eals the cluster emission to be complex and nonspherical, and yields a clus ter temperature of kT = 2.3(-0.8)(+1.8) keV and a 2.0 to 10 keV cluster lum inosity within a 1 Mpc radius of L-X = 7.6(-0.2)(+0.6) x 10(43) ergs s(-1) (error bars denote 90% confidence limits). Our mass estimate of the cluster within its virial radius is 2.3(-0.7)(+1.8) x 10(14) M-. and is a factor o f 2 smaller than, although consistent with, previous mass estimates based o n the observed cluster velocity dispersion.