The Catalog of Resolved Spectroscopic Binaries: Development and Description

Resolved spectroscopic binaries are unique among other types of binaries. They provide the only possibility (aside from trigonometric parallaxes) to accurately determine distances to objects, which is one of the most important characteristics in astronomy. Such binaries are not numerous, but an exhaustive catalog of them still does not exist. The authors have developed a pilot version of a new catalog of resolved spectroscopic binaries. It contains information about orbital elements, component masses, parallaxes, and other parameters for 107 stars. Thus, the catalog represents the most extensive list of resolved spectroscopic binaries known to date. A preliminary analysis of the distributions of the stellar parameters of the objects in the catalog has been carried out, as well as a comparison of the trigonometric parallaxes from Gaia DR3 with the orbital parallaxes. The article is partly based on a report presented at the conference “Modern Stellar Astronomy-2022,” which was held at the Caucasian Mountain Observatory of the Astronomical institute of Lomonosov Moscow State University on November 8–10, 2022.


INTRODUCTION
Resolved spectroscopic binaries (RSBs) are binary systems with solutions of the orbits obtained both from visual and spectroscopic data.A spectroscopic binary, being visually resolved, provides an indispensable opportunity to directly determine (rather than to estimate) the parallaxes and masses of stars.Such objects are relatively few in number, with no more than two hundred of them being known at the moment.An exhaustive catalog of resolved spectroscopic binaries does not currently exist, although there have been attempts to create one.In particular, 40 systems of this type with known orbital elements, component masses, brightness, and spectral classification were collected in [1].Over the following years, a significant number of RSBs have been discovered, with accumulated data presented mainly in scattered publications.
The aim of this study is to create a catalog containing the most complete information on all resolved spectroscopic binaries known at the moment.The following sections describe the preliminary version of the catalog.

THE STRUCTURE OF THE CATALOG
The catalog contains data on 107 resolved spectroscopic binaries collected from various sources.
Most of the objects and data about them were taken from [1,2], which provide the lists of 40 and 69 systems, respectively.These lists overlap significantly, and in such cases more recent data were included in the catalog.In addition, the papers [3][4][5][6] were used, as well as a number of other publications, each of which contains a detailed study of one binary system.In addition to the data from the publications listed above, the catalog includes parallaxes and brightness values from Gaia DR3 [7], as well as some information from the SIMBAD database.
A part of the table (see Table 1) consisting of five catalog entries is presented as an example.It does not provide all the parameters of the catalog stars, but only those that have the most informative significance.In the future, the format of the catalog will be modified.

THE ANALYSIS OF THE DATA
More than a third of the binaries in the catalog have periods shorter than 5 years (Fig. 1, left panel).The maximum period value among the catalog objects is years.We may tell that the stars of the catalog are uniformly distributed according to the values of the orbital elements, in particular, eccentricities (Fig. 1, right panel).
Figure 2 shows the period-eccentricity dependence for the binary systems of the catalog.The region of avoidance in the upper left corner of the plot (the = 318 P e absence of eccentric short-period orbits) is a consequence of the circularization of close systems.However, attention should also be drawn to the area of avoidance in the lower right corner of the plot (the absence of circular long-period orbits).Apparently, this is a manifestation of the selection effect: only when the periastron is sufficiently close to the focus, the velocity of a component at the periastron differs significantly from the average value and becomes detectable through the line shifts in the spectrum.In circular long-period orbits, the velocity is constant and low, and the system is unlikely to be detected spectroscopically.
Through the combination of parameters determined from the radial velocity curve and the orbital inclination obtained from visual observations, it possible to calculate the masses of the components.The distribution of the catalogued systems according to the masses of the components is shown in Fig. 3.
The values of trigonometric parallaxes from Gaia DR3 were compared with the orbital parallaxes to T e assess their agreement.Figure 4 shows that for more distant catalog objects, the discrepancies are minimal.This is due to Gaia's inability to determine binarity at large distances and, accordingly, the high accuracy of parallax determination.For nearby stars, the deviations from the linear dependence mostly correlate with the scale of the errors caused by the orbital motion.In addition, it can be seen that in some cases, the accuracy of determination of the orbital parallax is compa-rable to that of the trigonometric parallax or even exceeds it.We also note that for one of the catalogued stars (GJ 65) only the ground-based trigonometric parallax has been published, while for another one (HD 172865) the trigonometric parallax is unknown.
This section presents some of the distributions and dependences of the catalog object parameters obtained during the preliminary analysis.A pilot version of a new catalog of resolved spectroscopic binaries has been developed.Information about orbital elements, component masses, orbital parallaxes, and other parameters of 107 stars has been collected.The catalog contains the most extensive list of resolved spectroscopic binary systems currently known (presumably, about 75% of the total number of the objects of this type).A preliminary analysis of the distributions of parameters of the catalog objects has been carried out, including a comparison between the Gaia DR3 parallaxes and the orbital parallaxes.
In the future, it is planned to expand the catalog by including new objects and adding missing information about existing objects, as well as perform a more detailed statistical analysis of the data.

Fig. 1 .
Fig. 1.Distribution of catalog stars by periods (in years, to the left) and eccentricity (to the right).

Fig. 3 . 1 Fig. 4 .
Fig. 3.The masses of the components of resolved spectroscopic binaries in solar units.

Table 1 .
Orbital and physical parameters for five objects in the catalog of resolved spectroscopic binaries