KMT-2022-BLG-0086: Another binary-lens binary-source microlensing event

TL;DR

This paper analyzes a microlensing event that is best explained by a binary-lens binary-source model, providing insights into the lens system's nature and demonstrating the importance of detailed modeling in microlensing events.

Contribution

It presents the first detailed analysis favoring a binary-lens binary-source model over other models for this event, with Bayesian constraints on the lens system.

Findings

The event is best explained by a 2L2S model over a 3L1S model.

The lens system is likely a binary star at ~6 kpc.

Proper motion measurements support the 2L2S interpretation.

Abstract

We present the analysis of a microlensing event KMT-2022-BLG-0086 of which the overall light curve is not described by a binary-lens single-source (2L1S) model, which suggests the existence of an extra lens or an extra source. We found that the event is best explained by the binary-lens binary-source (2L2S) model, but the 2L2S model is only favored over the triple-lens single-source (3L1S) model by $\Delta\chi^{2} \simeq 9$. Although the event has noticeable anomalies around the peak of the light curve, they are not enough covered to constrain the angular Einstein radius $\theta_{\rm E}$, thus we only measure the minimum angular Einstein radius $\theta_{\rm E,min}$. From the Bayesian analysis, it is found that that the binary lens system is a binary star with masses of $(m_1,m_2)=(0.46^{+0.35}_{-0.25}\, M_\odot, 0.75^{+0.67}_{-0.55}\, M_\odot)$ at a distance of $D_{\rm L}=5.87^{+1.21}_{-1.79}$ kpc, while the triple lens system is a brown dwarf or a massive giant planet in a low-mass binary-star system with masses of $(m_1,m_2,m_3)=(0.43^{+0.41}_{-0.35}\, M_\odot, 0.056^{+0.055}_{-0.047}\, M_\odot, 20.84^{+20.20}_{-17.04}\, M_{\rm J})$ at a distance of $D_{\rm L}=4.06^{+1.39}_{-3.28}$ kpc, indicating a disk lens system. The 2L2S model yields the relative lens-source proper motion of $\mu_{\rm rel} \geqslant 4.6\, \rm mas\, yr^{-1}$ that is consistent with the Bayesian result, whereas the 3L1S model yields $\mu_{\rm rel} \geqslant 18.9\, \rm mas\, yr^{-1}$, which is more than three times larger than that of a typical disk object of $\sim 6\, \rm mas\, yr^{-1}$ and thus is not consistent with the Bayesian result. This suggests that the event is likely caused by the binary-lens binary-source model.