NICMOS and VLA observations of the gravitationally lensed ultraluminous BAL quasar APM 08279+5255:: Detection of a third image

We present a suite of observations of the recently identified ultraluminous BAL quasar APM 08279 + 5255, taken both in the infrared with the NICMOS high-resolution camera on board the Hubble Space Telescope and at 3.5 cm with the Very Large Array. With an inferred luminosity of similar to 5 x 10(15) L., APM 08279+5255 is apparently the most luminous system known. Extant ground-based images show that APM 08279+5255 is not pointlike, but is instead separated into two components, indicative of gravitational lensing. The much higher resolution images presented here also reveal two point sources, A and B, of almost equal brightness (f(B)/f(A) = 0.782 +/- 0.010), separated by 0." 378 +/- 0." 001, as well as a third, previously unknown, fainter image, C, seen between the brighter images. While the nature of C is not fully determined, several lines of evidence point to it being a third gravitationally lensed image of the quasar, rather than being the lensing galaxy. Simple models that recover the relative image configuration and brightnesses are presented. While proving to be substantially amplified, APM 08279 + 5255 possesses an intrinsic bolometric luminosity of similar to 10(14) --> 10(15) L. and remains amongst the most luminous objects known.