Very long baseline interferometry observations of the high-redshift X-ray-bright blazar SRGE J170245.3+130104

The X-ray luminous and radio-loud active galactic nucleus (AGN) SRGE J170245.3+130104 discovered at $z 5.5$ provides unique chances to probe the growth and evolution of a supermassice black hole (SMBH) with powerful jets in the early Universe. We present $1.35-5.1$ GHz Very Long Baseline Array (VLBA) results regarding the radio continuum emission and a spectral analysis of this quasar in a low-flux-density state. This source is unresolved at three frequencies, with total flux densities of $8.35 mJy \ mJy \ $, and $6.57 mJy \ $ at 1.73 GHz, 2.26 GHz, and 4.87 GHz, respectively. Meanwhile, the brightness temperature is higher than $10^9$ K. Compared with previous radio observations with arcsecond-scale resolution, nearly all the radio emission from this source is concentrated in the very central milliarcsecond (mas) scale area. We confirm this source is a bright blazar at $z>5$. This young AGN provides a great opportunity to understand the mechanisms behind the generation of strong jets in the early Universe.