arXiv subjects

Karel Píška

Publications and source records attributed to Karel Píška.

4 recordsLinked to original sources

arXiv2025

Kinematics of the Milky way from the statistical analysis of the Gaia Data Release 3

The aim of the analysis of data from the Gaia Space Observatory is to obtain kinematic parameters of the collective motion of stars in a part of our galaxy. This research is based on a statistical analysis of the motion of {$55,038,539$} stars selected in different directions from the Sun up to a distance of 3--6 kpc. We developed statistical methods for the analysis working with input data represented by the full astrometric solution (five parameters). Using the proposed statistical methods, we obtained the local velocity of the Sun $\left( U_{\odot}% ,V_{\odot},W_{\odot}\right) =(9.58,16.25,7.33)\pm(0.05,0.04,0.02)_{stat}% \pm(0.7,0.9,0.1)_{syst}$ km/s and the rotation velocity of the galaxy at different radii. For the Sun's orbit radius, we obtained the velocity of the galaxy rotation$\ V_{c}\approx234\pm4$ km/s. Collective rotation slows down in the region under study linearly with distance from the disk plane: $ΔV/ΔZ\cong33.5~\mathrm{km\,s}^{-1}\mathrm{kpc}^{-1}$. We showed that the different kinematic characteristics and distributions, which depend on the position in the galaxy, can be well described in the studied 3D region by a simple Monte Carlo simulation model, representing an axisymmetric approximation of the galaxy kinematics. The optimal values of the six free parameters were tuned by comparison with the data.

astro-ph.GA↗

arXiv2021

Catalogue of wide binary, trinary and quaternary candidates from the Gaia data release 2 (region $\left\vert b\right\vert >25\,°$)

The occurrence of multiple stars, dominantly binaries, is studied using the \textit{Gaia}-ESA DR2 catalogue. We apply the optimized statistical method that we previously developed for the analysis of 2D patterns. The field of stars is divided into a mosaic of small pieces, which represent a statistical set for analysis. Specifically, data input is represented by a grid of circles (events) with radius $0.02\,°$ covering the sky in the field of galactic latitude $\left\vert b\right\vert >25\,°$. The criteria for selecting candidates for multiple stars are based on two parameters: angular separation and collinearity of proper motion. Radial separation, due to limited accuracy, is used only as a weaker supplementary constraint. Due attention is paid to the accurate calculation of the background, which is a necessary input for evaluating the quality of the candidates. Our selection algorithm generates the catalogue of candidates: $900,842$ binaries, $5,282$ trinaries and $30$ quaternaries.

astro-ph.GA↗

arXiv2019

Statistical analysis of binary stars from the Gaia catalogue DR2

We have developed a general statistical procedure for analysis of 2D and 3D finite patterns, which is applied to the data from recently released Gaia-ESA catalogue DR2. The 2D analysis clearly confirms our former results on the presence of binaries in the former DR1 catalogue. Our main objective is the statistical 3D analysis of DR2. For this, it is essential that the DR2 catalogue includes parallaxes and data on the proper motion. The analysis allows us to determine for each pair of stars the probability that it is the binary star. This probability is represented by the function \b{eta}(Δ) depending on the separation. Further, a combined analysis of the separation with proper motion provides a clear picture of binaries with two components of the motion: parallel and orbital. The result of this analysis is an estimate of the average orbital period and mass of the binary system. The catalogue we have created involves 80560 binary candidates.

astro-ph.IM↗

arXiv2018

A statistical analysis of two-dimensional patterns and its application to astrometry

Here we develop a general statistical procedure for the analysis of finite two-dimensional (2D) patterns inspired by the analysis of heavy-ion data. The method is used in the study of publicly available data obtained by the Gaia-ESA mission. We prove that the procedure can be sensitive to the limits of accuracy of measurement, and can also clearly identify the real physical effects on the large background of random distributions. As an example, the method confirms the presence of binary and ternary star systems in the studied data. At the same time, the possibility of the statistical detection of the gravitational microlensing effect is discussed.

astro-ph.IM↗