Period Changes of 14,127 Contact Eclipsing Binaries in the Galactic Bulge

TL;DR

This study analyzes orbital period variations in over 14,000 contact eclipsing binaries in the Galactic bulge using OGLE data, classifying their period changes and identifying significant rates of increase and decrease.

Contribution

It provides a comprehensive classification and analysis of period changes in a large sample of contact eclipsing binaries, including new period measurements and statistical inference methods.

Findings

Most binaries show near-zero secular period change rates.

Identified binaries with the highest increasing and decreasing period rates.

Period distributions range from 0.235 to 0.990 days for inner binaries.

Abstract

We present the orbital period variations of 14,127 contact eclipsing binaries (CEBs) based on the OGLE-III\&IV observations in the Galactic bulge. New times of minimum lights for the CEBs were derived by binary modeling for the full seasonal light curves, which were made from survey observations at an interval of 1 year. The orbital period changes of the systems were classified based on the statistical inference, multiple-hypothesis testing error measure, and visual inspection of the eclipse timing diagrams. As the results, we identified 13,716 CEBs with a parabola, 307 CEBs with a sinusoid, and 104 CEBs with the two variations. The period distributions of the inner close binaries and the outer companions were in the ranges of $0.235-0.990$ days and $5.0-14.0$ years, respectively. In our sample of 13,820 CEBs showing a parabolic variation, the highest decreasing and increasing period rates were determined to be $\dot P=-1.38\pm0.06\times10^{-5}$ day year$^{-1}$ for OGLE-BLG-ECL-169991 and $\dot P=+8.99\pm0.44\times10^{-6}$ day year$^{-1}$ for OGLE-BLG-ECL-189805, respectively. The secular period change rates were distributed almost symmetrically around zero, and most of them lie within $\dot P=\pm5.0\times10^{-6}$ day year$^{-1}$.