OGLE-2016-BLG-0263L\lowercase{b}: Microlensing Detection of a Very Low-mass Binary Companion Through a Repeating Event Channel

TL;DR

This paper reports the discovery of a very low-mass planetary companion via a unique repeating microlensing event, highlighting the effectiveness of high-cadence surveys in detecting such distant, low-mass objects beyond the snow line.

Contribution

It introduces a novel detection channel for low-mass companions through repeating microlensing events, expanding the potential for future discoveries.

Findings

Detected a planet-mass companion with ~4.1 M_J via repeating microlensing.

Projected separation of the companion is about 6.5 au, beyond Neptune.

Highlights the role of high-cadence surveys in low-mass microlensing detections.

Abstract

We report the discovery of a planet-mass companion to the microlens OGLE-2016-BLG-0263L. Unlike most low-mass companions that were detected through perturbations to the smooth and symmetric light curves produced by the primary, the companion was discovered through the channel of a repeating event, in which the companion itself produced its own single-mass light curve after the event produced by the primary had ended. Thanks to the continuous coverage of the second peak by high-cadence surveys, the possibility of the repeating nature due to source binarity is excluded with a $96\%$ confidence level. The mass of the companion estimated by a Bayesian analysis is $M_{\rm p}=4.1_{-2.5}^{+6.5}\ M_{\rm J}$. The projected primary-companion separation is $a_\perp = 6.5^{+1.3}_{-1.9}$ au. The ratio of the separation to the snow-line distance of $a_\perp/a_{\rm sl}\sim 15.4$ corresponds to the region beyond Neptune, the outermost planet of the solar system. We discuss the importance of high-cadence surveys in expanding the range of microlensing detections of low-mass companions and future space-based microlensing surveys.