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Table 1:   Target stars. Columns: name - star name; l, b - Galactic coordinates (from SIMBAD); ,  - trigonometric parallax and its error (Hipparcos); K,  - the equivalent width of the Ca II K line and its error; H,  - the equivalent width of the Ca II H line and its error; ,  - Ca II column density and its error; as, as ref: association membership and reference: H stands for Humphreys (1978), GS for Garmany and Stencel (1992), Z for de Zeeuw et al. (1999).  - association distance (in parsecs) from Humphreys (1978);  - association distance from Garmany & Stencel (1992);  - association membership and distance from de Zeeuw et al. (1999); ,  - distance estimated from formula (3), and its formal error.