Physical and geometrical parameters of CVBS XIV: The two nearby systems HIP 19206 and HIP 84425

TL;DR

This paper determines the fundamental parameters of two nearby binary star systems using Gaia data, combining orbital and physical analysis methods to improve understanding of their formation and evolution.

Contribution

It introduces a combined approach using dynamical and atmospheric modeling methods to accurately estimate parameters of CVBMSs, including a new dynamical parallax.

Findings

The new dynamical parallax for HIP 19205 aligns with Gaia DR3 measurements.

All components are identified as solar-type main sequence stars.

Discrepancies between Gaia and Hipparcos parallaxes are addressed with a new parallax estimate.

Abstract

The data release DR2 of Gaia mission was of great help in precise determination of fundamental parameters of Close Visual Binary and Multiple Systems (CVBMSs), especially masses of their components, which are crucial parameters in understating formation and and evolution of stars and galaxies. This article presents the complete set of fundamental parameters of two nearby (CVBSs), these are HIP 19206 and HIP 84425. We used a combination of two methods; the first one is Tokovinin's dynamical method to solve the orbit of the system and to estimate orbital elements and the dynamical mass sum, and the second one is Al-Wardat's method for analyzing CVBMSs to estimate the physical parameters of the individual components. The latest method employs grids of Kurucz line-blanketed plane parallel model atmospheres to build synthetic Spectral Energy Distributions (SED) of the individual components. Trigonometric parallax measurements given by Gaia DR2 and Hipparcos catalogues are used to analyse the two systems. The difference in these measurements yielded slight discrepancies in the fundamental parameters of the individual components especially masses. So, a new dynamical parallax is suggested in this work based on the most convenient mass sum as given by each of the two methods. The new dynamical parallax for the system Hip 19205 as $22.97\pm 0.95$ mas coincides well with the trigonometric one given recently (in December 2020) by Gaia DR3 as $22.3689\pm 0.4056$ mas. The positions of the components of the two systems on the evolutionary tracks and isochrones are plotted, which suggest that all components are solar-type main sequence stars. Their most probable formation and evolution scenarios are also discussed.