2001ApJ...555....1M

We present results from X-ray observations of the quadruply lensed quasar RX J0911.4+0551 using data obtained with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory. The 29 ks observation detects a total of ∼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 optical measurements. When compared with contemporaneous optical data, one of the lensed images (component A3) is dimmer by a factor of ∼6 in X-rays with respect to the two brighter images (components A1 and A2). Spectral fitting for the combined images shows significant intrinsic absorption in the soft (0.2-2.4 keV) energy band, consistent with the mini-broad absorption line (BAL) nature of this quasar, while a comparison with ROSAT Position Sensitive Proportional Counter observations from 1990 shows a drop of ∼6.5 in the total soft bandpass flux. The observations also detect ∼157 X-ray photons arising from extended emission of the nearby cluster (peaked ∼42" southwest of RX J0911.4+0551) responsible for the large external shear present in the system. The Chandra observation reveals the cluster emission to be complex and nonspherical, and yields a cluster temperature of kT=2.3^+1.8_–0.8 keV and a 2.0 to 10 keV cluster luminosity within a 1 Mpc radius of L_X=7.6^+0.6_–0.2x10⁴³ ergs.s^–1 (error bars denote 90% confidence limits). Our mass estimate of the cluster within its virial radius is 2.3^+1.8_–0.7x10¹⁴ M_☉ and is a factor of 2 smaller than, although consistent with, previous mass estimates based on the observed cluster velocity dispersion.