Analysis of Gravitational Microlensing Event: OGLE-2018-BLG-0380

Sarang Shah  ✧  India Thirty Meter Telescope (TMT), India

We present the analysis of the microlensing event OGLE-2018-BLG-0380, which was observed towards the galactic bulge in the microlensing season of 2018. The light curve of this event had two prominent peaks and a third bump towards the decreasing side of the light curve. The \(t_\mathsf{E}\) of this event is \(\sim9\) days indicating a low mass lens if we assume the statistics of lens mass and \(t_\mathsf{E}\). The conventional modeling failed to give any solutions that could explain the light curve. So, we performed a heuristic analysis of the light curve and found that the binary lens orbital motion explains the third perturbation. This event peaked close to the vernal equinox of 2018. So, we also detect orbital parallax and orbiting binary ecliptic degeneracy in this event. Other cases like close-wide degeneracy and binary-lens-binary-source model are disfavoured by the likelihood values. The only acceptable model is a close binary lens with orbital motion. The source is a red giant in the bulge. Detecting finite source effects and significant orbital parallax allows us to characterize the lens mass and distance. Assuming the source to be at 8.2 Kpc, the distance to the lens is \(1.46 \pm 0.08\)kpc, and the lens is comprised of two super-Jupiter mass objects with \(m_1 = 6.44 \pm 1.42 M_\mathsf{Jupiter}\) and \(m_2 = 1.88 \pm 0.32 M_\mathsf{Jupiter}\). Are they a pair of freely floating planets or scaled-down versions of brown dwarfs?