Estimating masses of selected stars in the Pulkovo program by means of astrometry methods

Abstract

Stars of Pulkovo observatory program are observed on 65-cm refractor during many years for study their positions and movement. We represent example of two visual binary stars, for which orbits and masses of components were determined, and two astrometric stars, for which masses of their unseen companions have been estimated. The first stars are: ADS 14636 (61 Cygni) and ADS 7251 and others are: Gliese 623 and ADS 8035 (Alpha UMa). The direct astrometric methods were used for estimation of mass-ratio and masses. ADS 7251 INTRODUCTIONThe mass of the star is one of its most important characteristics. Amount of matter in a star determines its temperature and pressure in the center, and also determines other characteristics of the star and then its evolutionary path. Direct estimates of the mass of the star are made on the basis of the law of universal gravitation.The study of binary stars has allowed to establish the unity of Newton's laws in the Universe and to obtain the fundamental knowledge about the masses of stars on the basis of observations. The determination of the masses of the stars by classic way is done by means of positional astrometric observations of double stars with the high-precision instruments for a long time. Observations should cover a long time interval, or the period of revolution of a double star must be sufficiently short compared to the total observation period. We also need the exact value of the distances for stars and that means -the exact parallax for stars in the solar neighborhood. Other methods to calculate the mass are considered to be indirect, they are not built on the law of gravity, but on the analysis of the stellar properties (luminosity, temperature, radius) which are somehow connected with the mass.

Preface: Stars and interstellar medium

“…Photographic astrometry is discussed by Shakht et al (2018). They use plates taken with the Pulkovo 65cm (F = 10.4 m) refractor in 1958-2006. In this paper, the authors consider two visual binaries, for which Pulkovo observations made it possible to derive accurate orbits and component masses, and two astrometric binaries, where they were able to estimate masses of their unseen components.…”