Binary Orbit Determination by Using a Variety of Observational Data

Abstract

The binary orbit determination is a basic research area in astronomy, its main products are the kinematical parameters of binary, which contain the kinematical parameters of the mass center and the orbital parameters. These parameters are the necessary constituents of the astronomical reference frame with high precision and high density, and at the same time they provide a necessary kinematic basis to the studies of various observed phenomena of binaries. On the other hand, because the binary orbit determination is the only direct route to obtain the stellar masses, which is one of the most fundamental parameters in astronomy, it has received great attention from astronomers for a long time.

Present researches mainly focus on the orbit determination of binary by combining a variety of observational data.

First, by fitting the revised Hipparcos Intermediate Astrometric Data (HIAD), we determine the full orbits of the double-lined spectroscopic binary systems. By using a variety of tests, we obtain the reliable full orbital solutions and the component masses of 13 systems. For 7 of them, i.e., HIP 9121, 17732, 32040, 57029, 76006, 102431, and 116360, the full orbital solutions are determined here for the first time. In the fitting process, the efficiency is improved by developing a modified grid optimization method, which reduces the number of non-linear model parameters to one, and allows all parameters to be adjustable within a region centered at each grid point.

Second, photocentric orbital solutions of 51 single-lined spectroscopic binary systems are determined by fitting the revised HIAD. Then the full orbital solutions and the component masses are estimated by using the mass luminosity relation for the systems with the main sequence primary. Moreover, the observable ephemerides are further provided for the systems with the magnitude difference less than 5 mag.

Third, Gaia mission will bring us a large amount of astrometric data with high precision. This will promote the developing of the binary orbit determination. So, we carry out the pre-researches on the following two aspects. One is to discuss the role of the long term ground-based positional data in the orbit determination of the Gaia astrometric binaries. Simulations show that these positional data can significantly improve the efficiency of the orbit determination, especially for those binaries with periods from 8 to 25 years. Another is to discuss the role of the Gaia astrometric data in the orbit determination of the spectroscopic binaries. Analyses prove that full orbital solutions for over 80% of double-lined spectroscopic binaries with reliable spectroscopic orbits can be obtained by fitting the Gaia astrometric data. But for those single-lined, only photocentric orbital solutions can be obtained. In order to obtain their full orbital solutions, future ground-based observations are needed.