KMT-2021-BLG-0240: Microlensing event with a deformed planetary signal

The light curve of the microlensing event KMT-2021-BLG-0240 exhibits a short-lasting anomaly with complex features near peak at 0.1~mag level from single-lens single-source model. We conducted modeling lensing under various interpretations to reveal nature anomaly. It is found that cannot be explained usual model based on binary-lens (2L1S) or binary-source (1L2S) interpretation. However, 2L1S planet companion can describe part anomaly, suggesting may deformed by tertiary lens component close source. From additional modeling, we find all either triple-lens (3L1S) (2L2S) obtained 3L1S it difficult validate 2L2S because does not exhibit signatures induced source orbital motion and ellipsoidal variations expected separation between stars according We, therefore, conclude two distinguished available data, correct. According solution, planetary system sub-Jovian-mass planets in which have masses 0.32--0.47~$M_{\rm J}$ 0.44--0.93~$M_{\rm J}$, they orbit an M dwarf host. other hand, single mass $\sim 0.21~M_{\rm orbiting late K-dwarf host, binary composed primary subgiant turnoff star secondary G dwarf. distance varies depending solution: 7.0$~kpc solution 6.6$~kpc solution.