OGLE-2018-BLG-0584 and KMT-2018-BLG-2119: two microlensing events with two lens masses and two source stars

TL;DR

This paper reanalyzes two anomalous microlensing events and finds that their light curves are best explained by models involving two sources and two lenses, revealing complex binary systems.

Contribution

It introduces a 2L2S modeling approach to explain anomalous microlensing events that cannot be explained by traditional models, revealing new binary configurations.

Findings

Both events are best explained by 2L2S models with close and wide degeneracies.

OGLE-2018-BLG-0584 involves two K-type sources and two M-dwarf lenses.

KMT-2018-BLG-2119 involves a G and K source and an M dwarf with a brown dwarf lens.

Abstract

We conduct a systematic investigation of the microlensing data collected during the previous observation seasons for the purpose of reanalyzing anomalous lensing events with no suggested plausible models. We find that two anomalous lensing events OGLE-2018-BLG-0584 and KMT-2018-BLG-2119 cannot be explained with the usual models based on either a binary-lens single-source (2L1S) or a single-lens binary-source (1L2S) interpretation. We test the feasibility of explaining the light curves with more sophisticated models by adding an extra lens (3L1S model) or a source (2L2S model) component to the 2L1S lens-system configuration. We find that a 2L2S interpretation well explains the light curves of both events, for each of which there are a pair of solutions resulting from the close and wide degeneracy. For the event OGLE-2018-BLG-0584, the source is a binary composed of two K-type stars, and the lens is a binary composed of two M dwarfs. For KMT-2018-BLG-2119, the source is a binary composed of two dwarfs of G and K spectral types, and the lens is a binary composed of a low-mass M dwarf and a brown dwarf.