Chromospheric activity on the RS Canum Venaticorum binary SZ Piscium

Abstract

Aims. We present the new high-resolution echelle spectra of SZ Psc, obtained in Nov. 2004 and Sep.- Dec. 2006, and study its chromospheric activity. Methods. By means of the spectral subtraction technique, we analyze our spectroscopic observations including several optical chromospheric activity indicators (the He I D(3), Na I D(1), D(2), H alpha, and Ca II infrared triplet lines). Results. All indicators show that the chromospheric activity of the system is associated with the cooler component. We find that the values of EW(8542)/EW(8498) are in the range 1-3, which indicates optically thick emission in plage-like regions. The 2006 data suggest the presence of active longitude phenomena. For the Ca II 8542 and 8662 and the Ha lines, it seems that the excess emission is stronger near the two quadratures of system. This may be anti-correlated with the behavior of the Na I D(1) line. The absorption features are detected in the subtracted Ha lines, which could be explained by prominence-like extended material seen on the stellar disk or by mass transfer from the cooler component to the hotter one.