Ogle-2018-blg-0677lb: A super earth near the galactic bulge

Abstract

We report the analysis of the microlensing event OGLE-2018-BLG-0677. A small feature in the light curve of the event leads to the discovery that the lens is a star-planet system. Although there are two degenerate solutions that could not be distinguished for this event, both lead to a similar planet-host mass ratio. We perform a Bayesian analysis based on a Galactic model to obtain the properties of the system and find that the planet corresponds to a super-Earth/sub-Neptune with a mass $M_{\mathrm{planet}}={3.96}_{-2.66}^{+5.88}{\mathrm{M}}_{\oplus }$. The host star has a mass $M_{\mathrm{host}}={0.12}_{-0.08}^{+0.14}{\mathrm{M}}_{\odot }$. The projected separation for the inner and outer solutions are ${0.63}_{-0.17}^{+0.20}$~AU and ${0.72}_{-0.19}^{+0.23}$~AU respectively. At $\Delta {\chi }^2={\chi }^2(1L1S)-{\chi }^2(2L1S)=46$, this is by far the lowest $\Delta {\chi }^2$ for any securely-detected microlensing planet to date, a feature that is closely connected to the fact that it is detected primarily via a "dip" rather than a "bump".

15 page, 12 figures, Published in AJ