Radio Detection Of Vik J2318-3113, The Most Distant Radio-Loud Quasar (Z=6.44)

We 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 (1.2x10(26) W Hz(-1) at 5 GHz) compared to the optical luminosity (1.8x10(24) W Hz(-1) at 4400 angstrom) makes it the most distant radio-loud quasar observed so far, with a radio loudness R similar to 70 (R = L-5GHz/L-4400 angstrom). Moreover, the high bolometric luminosity of the source (L-bol=7.4x10(46) erg s(-1)) suggests the presence of a supermassive black hole with a high mass (greater than or similar to 6x10(8) M-circle dot) 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 similar to 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.