Orbits of visual double stars discovered by Otto Struve at Pulkovo

Abstract

Orbits of 17 visual double stars discovered by Otto Struve at Pulkovo STT 28, 75, 119,132, 182, 201, 228, 241, 250, 296, 369, 383, 424, 430, 435, 462, 520 are calculated for the first time. Both visual observations XIX–XX centuries by means of the micrometric technique and modern observations in according with the fourth interferometric catalog are used. All the presented stars had been observing for more than hundred years. But these observations cover arcs only from 10 to 50 degrees for this long-term interval. There are some problems of orbit determinations if a method based on the of short arc observations. The new method improving a method of Hartkopf et al is suggested in this work. The new method is globally converging and uses genetic algorithms for saving of time of calculations. It is possible to use additional data (sum of masses of the components and relative radial velocities) to increase the accuracy of the results. The relative radial velocities are unknown for presented 17 stars; therefore we use only masses of components which are obtained from photometric data of the Tycho catalog. All these stars are located far from the Sun, therefore their orbits can be considered as preliminary ones. With using the radial velocity value only the orbit of STT 547 is calculated. This is the control star, because there are a lot of variants of this orbit which has been obtained by different authors, and the radial velocities of components are well known. We obtained three variants of the orbit for this star. All the orbits fit with each other and the recent observations, and the calculated dynamic masses are in agreement with photometric data. Orientation of the received orbits in a galactic frame is also calculated and for 11 of 18 cases the planes of the orbits are steeply inclined to the Galaxy plane.