The First Orbits of Six Wide Double Stars in the Solar Neighborhood Based on Gaia DR2 Observations
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First Orbits of Six Wide Double Stars in the Solar Neighborhood Based on Gaia DR2 Observations O. V. Kiyaeva1* and L. G. Romanenko1 1
Pulkovo Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65, St. Petersburg, 196140 Russia Received May 13, 2020; revised May 30, 2020; accepted June 1, 2020
Abstract—The apparent motion parameter (AMP) method is designed to determine the orbits of wide pairs of double stars with orbital periods of hundreds and thousands of years. This is a dynamical method using all that is known about the star at one moment to reconstruct its complete orbit within the two-body problem. The Gaia DR2 catalog contains all of the data for epoch 2015.5 that are needed to use the AMP method if the relative motion reflects an unperturbed orbital motion. We demonstrate the possibilities of the method to determine the orbits of individual stars. Six stars have been investigated. For the triple star ADS 7034 we have determined the orbit of the inner pair, the set of orbits of the outer pair, and the stability region of the triple system for the first time. Using the double star ADS 9357 as an example, we show that for the determination of the orbits of individual stars the AMP method has an advantage over the geometrical methods using the Thiele–Innes equations on short arcs covered by observations. The orbits with periods more than 1000 years have been determined for the first time for three stars: ADS 7588, ADS 8561, and ADS 9048. For WDS 14051+4913 it is impossible to determine a reliable orbit, a preliminary family of orbits has been obtained, and a companion is suspected. We give a list of problem stars for which the orbits have not been determined, but the presence of a companion is possible. DOI: 10.1134/S1063773720070063 Keywords: double stars, orbits from short arcs.
INTRODUCTION Wide, slowly revolving double and multiple stars are deprived of the attention of researchers, because a short orbital arc has been covered by observations since their discovery until now. At the Pulkovo Observatory we attempted to compensate for this shortcoming by carrying out homogeneous observations with one telescope (26-inch refractor) for many years and the apparent motion parameter (AMP) method was specially proposed to determine the orbits (see Kiselev and Kiyaeva 1980), which was used previously to determine the orbit of an artificial Earth satellite from one photograph with many exposures (Kiselev and Bykov 1973). Laplace’s idea underlies all of the dynamical methods. Its essence is as follows: if for a body moving under the action of a central force the position, velocity, and acceleration of its apparent motion are known at some moment, then, given the position and motion of the observer, the spatial position and velocity vectors and, consequently, the orbit can be determined. In the 20th century this idea was implemented in various *
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modifications to determine the orbits of double stars from short arcs (see, e.g., Hopmann 1960; Hauser and Marcy 1999). One of the modifi
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