Contents

Astronomy Letters

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Vol. 47, No. 3, 2021

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Discovery of the Most X-ray Luminous Quasar SRGE J170245.3+130104 at Redshift $\boldsymbol{z\approx 5.5}$

G. A. Khorunzhev, A. V. Meshcheryakov, P. S. Medvedev, V. D. Borisov, R. A. Burenin, R. A. Krivonos, R. I. Uklein, E. S. Shablovinskaya, V. L. Afanasiev, S. N. Dodonov, R. A. Sunyaev, S. Yu. Sazonov, and M. R. Gilfanov p. 123  abstract

Spectroscopic Redshift Measurements for Galaxy Clusters from the Lockman Hole Survey with the eROSITA Telescope Onboard the SRG Observatory

I. A. Zaznobin, R. A. Burenin, A. R. Lyapin, G. A. Khorunzhev, V. L. Afanasiev, A. A. Grokhovskaya, S. N. Dodonov, M. V. Eselevich, R. I. Uklein, I. F. Bikmaev, I. M. Khamitov, M. R. Gilfanov, N. S. Lyskova, P. S. Medvedev, and R. A. Sunyaev p. 141  abstract

Extended Emission of Cosmic Gamma-Ray Bursts Detected in the SPI-ACS/INTEGRAL Experiment

G. Yu. Mozgunov, P. Yu. Minaev, and A. S. Pozanenko p. 150  abstract

To the Globular Cluster Classification Problem. Calculating the Concentration of Stars for 26 Clusters

S. N. Nuritdinov, I. U. Tatjibaev, and A. S. Rastorguev p. 163  abstract

The Dichotomy of the Mass-radius Relation and the Number of Globular Clusters*

Ahmed H. Abdullah and Pavel Kroupa p. 170  abstract

Activity of the Star AB Pic with an Exoplanet from the Young Tuc–Hor Association

I. S. Savanov p. 175  abstract

Study of Close Stellar Encounters with the Solar System Based on Data from the Gaia EDR3 Catalogue

V. V. Bobylev and A. T. Bajkova p. 180  abstract

Analysis of Optimal Flight Trajectories to the Trans-Neptunian Object (90377) Sedna

V. A. Zubko, A. A. Sukhanov, K. S. Fedyaev, V. V. Koryanov, and A. A. Belyaev p. 188  abstract

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