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We present a spectral study of the single magnetically active K giant OP Andin the period 1979 -- 2018, monitoring the variability of the activityindicator line H${\alpha}$. Original data obtained in the period 2015 -- 2018with the echelle spectrograph ESpeRo at the 2m telescope of the NationalAstronomical Observatory Rozhen in Bulgaria, previously unpublished originaldata obtained in the period 1997 -- 2007 and on one night in 2013 with theCoude spectrograph at the same telescope, as well as data from the literatureare presented in this study. The variability of the H${\alpha}$ line revealsthat the activity level of OP And is higher in the period 1993 -- 2000, whileduring the period 2008 -- 2010 it is lower, possibly close to a minimum. Also,our data for the period 2015 -- 2018 show that the activity level is increasingagain. Spectral observations of the activity indicators CaII H&K lines and CaIIIR triplet are sparse during the studied period. We use such ones when possibleto confirm the detection of some flare events. The structure of H${\alpha}$changes with the activity level: when the activity is higher, we observe ablue-shifted component of this line, interpreted as an expanding area above thephotosphere, but during a lower activity period it is almost absent. Ourresults are in a good agreement with the idea that the magnetic field controlsthe mass outflow in this giant. More years of observations are necessary todetermine the eventual activity cycle of OP And.

A Long-Term Spectral Study of the Single Active Giant OP Andromedae