Ighina, L.L.IghinaBelladitta, S.S.BelladittaCACCIANIGA, AlessandroAlessandroCACCIANIGABroderick, J. W.J. W.BroderickDrouart, G.G.DrouartMORETTI, AlbertoAlbertoMORETTISeymour, N.N.Seymour2021-09-272021-09-2720210004-6361http://hdl.handle.net/20.500.12386/31049We report the 888 MHz radio detection in the Rapid ASKAP Continuum Survey (RACS) of VIK J2318−3113, a z = 6.44 quasar. Its radio luminosity (1.2 × 10^26 W Hz^−1 at 5 GHz) compared to the optical luminosity (1.8 × 10^24 W Hz^−1 at 4400 Å) makes it the most distant radio-loud quasar observed so far, with a radio loudness R ∼ 70 (R = L_5 GHz/L4400 Å). Moreover, the high bolometric luminosity of the source (L_bol = 7.4 × 10^46 erg s^−1) suggests the presence of a supermassive black hole with a high mass (≳6 × 10^8 M⊙) at a time when the Universe was younger than a billion years. Combining the new radio data from RACS with previous ASKAP observations at the same frequency, we found that the flux density of the source may have varied by a factor of ∼2, which could suggest the presence of a relativistic jet oriented towards the line of sight, that is, a blazar nature. However, currently available radio data do not allow us to firmly characterise the orientation of the source. Further radio and X-ray observations are needed.STAMPAenArticle10.1051/0004-6361/2021403622-s2.0-85103078693WOS:000631888900001https://www.aanda.org/articles/aa/full_html/2021/03/aa40362-21/aa40362-21.html2021A&A...647L..11IFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_10 High energy and particle astronomy – X-rays, cosmic rays, gamma rays, neutrinos