Spectroscopic and photometric confirmation of chromospheric activity in four stars

摘要: We present analysis of medium resolution optical spectra and long term V band photometry four cool stars, BD+13 5000, BD+11 3024, TYC 3557-919-1 5163-1764-1. Our spectroscopic reveals that the stars are giant or sub-giant from K0 K1 spectral type, all them exhibit emission features in their Ca ii H& K lines. These appear to be modulated with rotation stars. Except we observe radial velocities target not stable, which suggests each might a member binary system. Global photometric data indicates clear cyclic variation for 5000 5163-1764-1 period 8.0$\pm$0.3 5.04$\pm$0.04 year, respectively. Besides that, dramatic increase ($\sim$0\fm7) mean brightness accompanied 2.87$\pm$0.12 variation, embedded into global brightening trend, possible multiple cycles on this star.