HD 8357

AR Piscium is a binary star system in the northern constellation of Canes Venatici, abbreviated AR Psc. It has the Henry Draper Catalogue identifier HD 8357; AR Piscium is its variable star designation. The pair have a combined apparent visual magnitude that fluctuates around 7.24, which is too faint to be readily visible to the naked eye. Parallax measurements place it at a distance of 148 light years from the Sun. The motion of this star through the Milky Way suggests it is a member of the intermediate disc population.

Variable X-ray source H0123+075 was identified from the HEAO 1 A-2 experiment and published by F. E. Marshall and associates in 1979. The following year, M. Garcia and associates identified the most probable source star as HD 8357, and determined it to be a RS Canum Venaticorum variable. This has a spectral class of G5 in the Henry Draper Catalogue. Optical observations by D. S. Hall and associates in 1980–1981 confirmed the source star to be optically variable with a period of $20.59$. In 1993, AR Psc was identified as an extreme ultraviolet source by K. A. Pounds and associates using ROSAT.

This is a double-lined spectroscopic binary with an orbital period of 14.3 days and an eccentricity of 0.185. The mass ratio of the two components is $14.302 days$. The primary component is an evolving subgiant star with a stellar classification of Kl IV. It is the chromospherically active member of this system, displaying visual flares. Intense X-ray flares have been detected. The smaller and less massive secondary star is a G-type main-sequence star with a stellar class of G7 V. Based on the significant difference between the orbital and photometric periods, the two stars are in pseudosynchronous rotation.