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SRGE J170245.3+130104 was discovered by the eROSITA telescope aboard the SRG space observatory on March 13-15, 2020 during the first half-year scan of its all-sky X-ray survey. The optical counterpart of the X-ray source was photometrically identified as a distant quasar candidate at $zapprox5.5$. Follow-up spectroscopic observations, done in August/September 2020 with the SCORPIO-II instrument at the BTA 6-m telescope, confirmed that SRGE J170245.3+130104 is a distant quasar at redshift z=5.466. The X-ray luminosity of the quasar during the first half-year scan of the eROSITA all-sky survey was $3.6^{+2.1}_{-1.5}times 10^{46}$ erg/s (in the 2-10 keV energy range), whereas its X-ray spectrum could be described by a power law with a slope of $Gamma=1.8^{+0.9}_{-0.8}$. Six months later (September 13-14, 2020), during the second half-year scan of the eROSITA all-sky survey, the quasar was detected again and its X-ray luminosity had decreased by a factor of 2 (at the $approx 1.9sigma$ confidence level). The SRGE J170245.3+130104 proves to be the most X-ray luminous among all known X-ray quasars at $z>5$. It is also one of the radio-loudest distant quasars (with radio-loudness $Rsim10^3$), which may imply that it is a blazar. In the Appendix, we present the list of all $z>5$ quasars detected in X-rays to date.
We present results from a 20 ks XMM-Newton DDT observation of the radio-load quasar CFHQS J142952+544717 at z=6.18, whose extreme X-ray luminosity was recently revealed by the SRG/eROSITA telescope in the course of its first all-sky survey. The quasa
We report the discovery of X-ray emission from CFHQS J142952+544717, the most distant known radio-loud quasar at z=6.18, on Dec. 10--11, 2019 with the eROSITA telescope on board the SRG satellite during its ongoing all-sky survey. The object was iden
We present new X-ray observations of luminous heavily dust-reddened quasars (HRQs) selected from infrared sky surveys. HRQs appear to be a dominant population at high redshifts and the highest luminosities, and may be associated with a transitional b
The intergalactic medium was not completely reionized until approximately a billion years after the Big Bang, as revealed by observations of quasars with redshifts of less than 6.5. It has been difficult to probe to higher redshifts, however, because
We report on the second installment of an X-ray monitoring project of seven luminous radio-quiet quasars (RQQs). New {sl Chandra} observations of four of these, at $4.10leq zleq4.35$, yield a total of six X-ray epochs, per source, with temporal basel