New Orbit and Estimate of the Mass of the Star 61 Cygni Based on Observations of it in 1819-2019

This paper is a continuation of our earlier work devoted to determining the orbit and mass of the star 61 Cyg and the changes in the photometric characteristics of its components. The purpose of this work has been to refine the orbital elements, estimate the masses, and search for possible manifestations of periodic components in deviations from the orbital motion. Observations on two instruments at the Pulkovo Observatory have been used in this work: the normal astrograph during 1895-1919 and the 26-inch refractor during 1957-2019, as well as the earliest micrometric measurements by V. Ya. (F.G.W.) Struve during 1819-1837. Relative positions of the components determined from observations with the normal astrograph during 1895-1999 are published for the first time. Because of its closeness to the Sun and the spectral class of the components K5V and K7V, 61 Cyg is regarded as a probable candidate parent star of an exoplanet. Because of the combined observations with the 26-inch refractor and the transformation of all the data to a unified system, a gap in the observations from the beginning of the twentieth century has been filled. The modern astrophysical parameters of this star together with data published in the Gaia DR2 survey have been used. To check the orbit, the radial orbital acceleration W has been calculated from our data and found to be in good agreement with the acceleration derived by other authors from spectral observations. Possible periodic deviations from the orbital motion of the star are also discussed.