1994A&A...291..135D

Ultraviolet and optical data are used to look at surface inhomogeneities on the active close binary system SZ Piscium. Lower chromospheric emission lines such as Mg II h&k, and to a lesser extend the upper chromospheric/lower transition region lines of O I 1305A and C II 1335A show a pronounced decrease when the F star is eclipsing the K sub-giant. However, higher temperature lines such as the resonance line of C IV 1550A do not show any change in flux. This suggests the presence of a plage with a high contrast at lower temperatures with a Mg II plage-to-K-star ratio of 5. Alternative explanations are explored. Monitoring of this system in the optical U-band and the ultraviolet lines such as C IV 1550A, indicates frequent high energy (10³⁵-10³⁶erg) flares.