2025ApJ...986..141P

We present the multiband photometric and low-resolution spectroscopic analysis of four W Ursae Majoris eclipsing binaries (EWs)-J080510.1+141528 (hereinafter as J0805a), J080516.3+143138 (hereinafter as J0805b), J143358.7+053953 (hereinafter as J1433), and J143458.4+054143 (hereinafter as J1434). The multiband ground based photometric data are collected using the 1.3 m Devasthal Fast Optical Telescope, while we also make use of Transiting Exoplanet Survey Satellite (TESS) photometric observations. The spectroscopic analysis is based on the low-resolution observations by the 4 m Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The ephemerides of these systems are updated using the photometric data from TESS and other photometric surveys. The system J0805b shows a secular change in the orbital period with a period change rate of 4.2 (±0.1) × 10^–7 days per year, while the orbital period change rate for J1433 is calculated as -1.1 (±0.1) × 10^–6 days per year. The mass-transfer rate for J0805b is found to be dM₁/dt = -1.56(±0.07) × 10^–6M_⊙ yr^–1 and dM₁/dt = -7.95(±0.87) × 10^–7M_⊙ yr^–1 for J1433. All the systems have inclination > 79^∘except J1433, which has an inclination of 72$\mathop{.}\limits^{\unicode{x000b0}}$8. The mass ratios (less massive to more massive component) for these targets are <0.5. All the systems except J0805b are A-subtype contact binaries. The absolute parameters of the systems are determined using Gaia DR3 parallax and reddening information. The LAMOST spectra are analyzed using the spectral subtraction technique. A small excess emission is detected for J1433 in H_α and H_β region. The systems are plotted on a Hertzsprung-Russell diagram and compared with previously studied systems. The mass ratio versus radius ratio relation is also investigated for these systems.