KMT-2021-BLG-1898: Planetary microlensing event involved with binary source stars

The light curve of the microlensing event KMT-2021-BLG-1898 exhibits a short-term central anomaly with double-bump features that cannot be explained by usual binary-lens or binary-source interpretations. With aim interpreting anomaly, we analyze lensing under various sophisticated models. We find is model, in which both lens and source are binaries (2L2S model). For this interpretation, planetary system planet/host mass ratio $q\sim 1.5\times 10^{-3}$, binary composed turn off subgiant star mid K dwarf. feature can also depicted triple-lens model (3L1S model), containing two planets. Among interpretations, 2L2S favored over 3L1S not only because it yields better fit to data, $\Delta\chi^2=[14.3$--18.5], but Einstein radii derived independently from stars result consistent values. According third occurring on stellar system, following MOA-2010-BLG-117 KMT-2018-BLG-1743. Under identify solutions resulting close-wide degeneracy determining planet-host separation. From Bayesian analysis, estimate planet has $\sim 0.7$--0.8~$M_{\rm J}$, orbits an early M dwarf host 0.5~M_\odot$. projected separation 1.9$~AU 3.0$~AU according close wide solutions, respectively.