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We present microlensing planet OGLE-2017-BLG-0173Lb, with planet-host mass ratio either $qsimeq 2.5times 10^{-5}$ or $qsimeq 6.5times 10^{-5}$, the lowest or among the lowest ever detected. The planetary perturbation is strongly detected, $Deltachi^2sim 10,000$, because it arises from a bright (therefore, large) source passing over and enveloping the planetary caustic: a so-called Hollywood event. The factor $sim 2.5$ offset in $q$ arises because of a previously unrecognized discrete degeneracy between Hollywood events in which the caustic is fully enveloped and those in which only one flank is enveloped, which we dub Cannae and von Schlieffen, respectively. This degeneracy is accidental in that it arises from gaps in the data. Nevertheless, the fact that it appears in a $Deltachi^2=10,000$ planetary anomaly is striking. We present a simple formalism to estimate the sensitivity of other Hollywood events to planets and show that they can lead to detections close to, but perhaps not quite reaching, the Earth/Sun mass ratio of $3times 10^{-6}$. This formalism also enables an analytic understanding of the factor $sim 2.5$ offset in $q$ between the Cannae and von Schlieffen solutions. The Bayesian estimates for the host-mass, system distance, and planet-host projected separation are $M=0.39^{+0.40}_{-0.24},M_odot$, $D_L=4.8^{+1.5}_{-1.8},kpc$, and $a_perp=3.8pm 1.6,au$. The two estimates of the planet mass are $m_p=3.3^{+3.8}_{-2.1},M_oplus$ and $m_p=8^{+11}_{-6},M_oplus$. The measured lens-source relative proper motion $mu=6,masyr$ will permit imaging of the lens in about 15 years or at first light on adaptive-optics imagers on next-generation telescopes. These will allow to measure the host mass but probably cannot resolve the planet-host mass-ratio degeneracy.
We report a giant exoplanet discovery in the microlensing event OGLE-2017-BLG-1049, which is a planet-host star mass ratio of $q=9.53pm0.39times10^{-3}$ and has a caustic crossing feature in the Korea Microlensing Telescope Network (KMTNet) observati
We report the discovery of microlensing planet OGLE-2017-BLG-0373Lb. We show that while the planet-host system has an unambiguous microlens topology, there are two geometries within this topology that fit the data equally well, which leads to a facto
We report the analysis of planetary microlensing event OGLE-2018-BLG-1185, which was observed by a large number of ground-based telescopes and by the $Spitzer$ Space Telescope. The ground-based light curve indicates a low planet-host star mass ratio
We report the discovery of a planetary system in which a super-earth orbits a late M-dwarf host. The planetary system was found from the analysis of the microlensing event OGLE-2017-BLG-0482, wherein the planet signal appears as a short-term anomaly
We report the discovery of a cold Super-Earth planet (m_p=4.4 +/- 0.5 M_Earth) orbiting a low-mass (M=0.23 +/- 0.03 M_Sun) M dwarf at projected separation a_perp = 1.18 +/- 0.10 AU, i.e., about 1.9 times the snow line. The system is quite nearby for