Probable brown dwarf companions detected in binary microlensing events during the 2018-2020 seasons of the KMTNet survey

Aims. We inspect the microlensing data of the KMTNet survey collected during the 2018-2020 seasons in order to find lensing events produced by binaries with brown dwarf (BD) companions. Methods. In order to pick out binary-lens events with candidate BD lens companions, we conducted systematic analyses of all anomalous lensing events observed during the seasons from 2018 to 2020. By applying a selection criterion of mass ratio between the lens components of 0.03 less than or similar to q less than or similar to 0.1, we identify four binary-lens events with candidate BD companions, namely KMT-2018-BLG-0321, KMT-2018-BLG-0885, KMT-2019-BLG-0297, and KMT-2019-BLG-0335. For the individual events, we present interpretations of the lens systems and measure the observables that can be used to constrain the physical lens parameters. Results. The masses of the lens companions estimated from the Bayesian analyses based on the measured observables indicate high probabilities that the lens companions are in the BD mass regime; that is, 59%, 68%, 66%, and 66% for the four respective events.

Automated summary

We inspect the microlensing data of the KMTNet survey collected from 2018 to 2020 to find lensing events produced by binaries with brown dwarf companions. By conducting systematic analyses of the anomalous lensing events observed during this period, we identify four binary-lens events with candidate brown dwarf companions. Bayesian analyses based on the measured observables indicate high probabilities (59%, 68%, 66%, and 66%) that the lens companions are in the brown dwarf mass regime.