OGLE-2017-BLG-0482Lb: A Microlensing Super-Earth Orbiting a Low-mass Host Star
2018
We report the discovery of a
planetary systemin which a
super-earthorbits a late M-dwarf host. The
planetary systemwas found from the analysis of the microlensing event OGLE-2017-BLG-0482, wherein the
planetsignal appears as a short-term anomaly to the smooth lensing
light curveproduced by the host. Despite its weak signal and short duration, the planetary signal was firmly detected from the dense and continuous coverage by three microlensing surveys. We find a
planet/host mass ratio of $q\sim 1.4\times 10^{-4}$. We measure the
microlens
parallax$\pi_{\rm E}$ from the long-term deviation in the observed lensing
light curve, but the angular
Einstein radius$\theta_{\rm E}$ cannot be measured because the source trajectory did not cross the
planet-induced caustic. Using the measured event timescale and the
microlens
parallax, we find that the masses of the
planetand the host are $M_{\rm p}=9.0_{-4.5}^{+9.0}\ M_\oplus$ and $M_{\rm host}=0.20_{-0.10}^{+0.20}\ M_\odot$, respectively, and the projected separation between them is $a_\perp=1.8_{-0.7}^{+0.6}$ au. The estimated distance to the lens is $D_{\rm L}=5.8_{-2.1}^{+1.8}$ kpc. The discovery of the
planetary systemdemonstrates that microlensing provides an important method to detect
low-mass
planetsorbiting
low-massstars.
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