Chromospherically active stars. XVIII. Sorting out the variability of HD 95559 and Gliese 410=DS Leonis

We have obtained spectroscopy and photometry of HD 95559 and photometry of Gliese 410 = DS Leonis. HD 95559 consists of a pair of essentially identica l K1 V stars, whose orbital period we refine to 1,52599775 +/- 0.00000104 d ays. The system is photometrically variable with a mean period of 1.5264 +/ - 0.0003 days. Despite minimum masses greater than 0.8 M-. for each compone nt, a search for eclipses proved negative. The lithium abundances of the co mponents of HD 95559 indicate that the system is younger than the Hyades cl uster, and its components may even have just arrived on the zero-age main s equence. Gl 410 = DS Leo is also a photometric variable, but we conclude th at the photometric period originally ascribed to this star is an alias of t he period for HD 95559. We find periods of 13.99 and 15.71 days for the fir st and second seasons of observation, respectively. Both HD 95559 and Gl 41 0 are BY Draconis variables, with variability resulting from the rotational modulation of starspots. We also find HR 4269, the check star for our phot ometry of HD 95559 and Gl 410, to be a variable K4 III with a photometric p eriod of 26.4 days in the first season of observation and periods of 13.96 and 83 days in the second. We suggest that its variability mechanism is rad ial pulsation, the same as that for M giant semiregular variables.