NuSTAR DETECTION OF THE BLAZAR B2 1023+25 AT REDSHIFT 5.3
Sbarrato, T. ; Tagliaferri, G. ; Ghisellini, G. ; ...Giommi, P. ; et al.
Nov - 2013
DOI: 10.1088/0004-637X/777/2/147
ISSN : 0004-637X ;
journal : The Astrophysical Journal

Volume : 777 ; Issue : 2
type: Article Journal

Abstract
B2 1023+25 is an extremely radio-loud quasar at z = 5.3 that was first identified as a likely high-redshift blazar candidate in the SDSS+FIRST quasar catalog. Here, we use the Nuclear Spectroscopic Telescope Array (NuSTAR) to investigate its non-thermal jet emission, whose high-energy component we detected in the hard X-ray energy band. The X-ray flux is (5-10?keV) and the photon spectral index is ?X 1.3-1.6. Modeling the full spectral energy distribution, we find that the jet is oriented close to the line of sight, with a viewing angle of 3?, and has significant Doppler boosting, with a large bulk Lorentz factor 13, which confirms the identification of B2 1023+25 as a blazar. B2 1023+25 is the first object at redshift larger than 5 detected by NuSTAR, demonstrating the ability of NuSTAR to investigate the early X-ray universe and to study extremely active supermassive black holes located at very high redshift.

keywords : High Energy Astrophysics,NuSTAR,X-rays: general,galaxies: active,quasars: general,quasars: individual (B2 1023+25)