1998ApJ...505..529I

We report on the discovery of a highly luminous, broad absorption line quasar at a redshift of z = 3.87, which is positionally coincident, within 1", with the IRAS Faint Source Catalog source F08279+5255. A chance alignment of the quasar and the IRAS source is extremely unlikely, and we argue that the optical and far-infrared flux are different manifestations of the same object. With an R-band magnitude of 15.2 and an IRAS 60 µm flux of 0.51 Jy, APM 08279+5255 is (apparently) easily the most intrinsically luminous object known, with L_Bol ∼ 5x10¹⁵ L_☉. Optical CCD photometry of the system, taken in good seeing, shows evidence that the system is slightly elongated. Although these data are consistent with the superposition of the quasar on a vastly luminous galaxy, we argue that a more likely scenario is that the optical image implies the presence of two unresolved point sources. Such a configuration suggests that gravitational lensing may play a significant role in amplifying the intrinsic properties of the system. Point-spread function fitting of two discrete sources gives a separation of ∼0".4 and an intensity ratio ∼1.1. The optical spectrum of the quasar clearly reveals the presence of three potential lensing galaxies, Mg II absorption systems at z = 1.18 and z = 1.81, and a damped Lyα absorption system at z = 3.07. Additional, as yet unseen, lensing galaxies may also be present. We estimate the total amplification of the optical component to be ~40 but, owing to the larger scale of the emitting region, would expect the infrared amplification to be significantly less. Even making the conservative assumption that all wavelengths are amplified by a factor 40, APM 08279+5255 still possesses a phenomenal luminosity of ≳10¹⁴ L_☉, indicating that it belongs to a small but significant population of high-redshift, hyperluminous objects with copious infrared emission.