摘要：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 of ${M}_{\mathrm{planet}}={3.96}_{-2.66}^{+5.88}{M}_{\oplus }$.The host star has a mass of ${M}_{\mathrm{host}}={0.12}_{-0.08}^{+0.14}\,{M}_{\odot }$.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 ${\rm{\Delta }}{\chi }^{2}={\chi }^{2}(1{\rm{L}}1{\rm{S}})-{\chi }^{2}(2{\rm{L}}1{\rm{S}})=46$, this is by far the lowest Δχ2 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.".
