PKS 0537-286

PKS 0537-286 (referred to QSO 0537-286), also known as QSO B0537-286, is a quasar located in the constellation Columba. With a redshift of 3.104, the object is located 11.4 billion light years away and belongs to the flat spectrum radio quasar blazar subclass (FSQR). It is one of the most luminous known high-redshift quasars.

Observation history
First detected at radio frequencies in 1975, PKS 0537-286 was observed at X-rays by the Einstein observatory. It was later studied by ASCA, ROSAT, XMM and subsequently Swift. These observations showed PKS 0537-286 as extremely luminous quasar ( Lx=1047 erg s−1 in the 0.1-2 keV range) with a particularly hard spectrum (r = 1 measured by Swift/BAT), which in the γ-ray band, it shows an energy flux of (1.44 ± 0.006) × 10−11 erg cm−2 s−1 in the fourth catalogue of Fermi-LAT active galactic nuclei. A weak iron K emission line and reflection features is also found in PKS 0537-286. Moreover, Sowards-Emmerd et al. (2004) identified the quasar as probable counterpart of the EGRET source 3EG J0531-2940.

Characteristics
PKS 0537-286 is the brightest blazar beyond z = 3.0. It shows characteristic properties of blazars, such as (rapid variability, strong polarization and high brightness) which are widely attributed to a powerful relativistic jet oriented close to the line of sight.

Moreover, in several occasions, γ-ray flares were observed when the daily flux was above 10−6 photon cm−2 s−1. This makes PKS 0537-286 the most distant γ-ray flaring blazar. The broad-band emission from PKS 0537-286 was successfully modelled within a one-zone synchrotron and external inverse Compton scenario where the excess in optical and ultraviolet bands was interpreted as emission from bright thermal accretion disc. Moreover, PKS 0537-286 shows an emission redshift of 3.11, a prominent absorption system at a redshift of 2.976, and a strong discontinuity at the Lyman-continuum edge in the absorption system.