Magnetic Activity on Four Short-period Contact Binaries: V0576 Peg, KW Psc, V0873 Per, and FY Boo

Abstract

We presented new photometry for four short-period late-type binaries, observed by three small telescopes in China from 2020 September to 2021 December. Seven sets of light curves (including the TESS data for FY Boo) were analyzed by using the W-D method. Three binaries (V0576 Peg, V0873 Per, and FY Boo) are W-type binaries with q ≃ 2.5, while KW Psc is an A-type binary with q ≃ 0.43. Max.I−Max.II is up to 10% of variable light amplitude for the asymmetric light curves, which are modeled by a dark spot on the surface of the more massive component. Photometric results imply the existence of movement and evolution of the cool spot. From the temperature−luminosity and mass–luminosity diagrams, the more massive components are a bit evolved main-sequence stars, while the less massive ones are oversized and overluminous owing to energy exchange. Orbital period analyses indicate that the cyclic oscillations occur in the (O − C) curves. Their modulated periods approach 11 yr, which may preferably result from the magnetic activity cycle for four late-type contact binaries. With angular momentum loss through magnetic braking, these short-period contact binaries may evolve into deep-contact configurations.