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Register a new userKMT-2016-BLG-1836Lb: A Super-Jovian Planet From A High-Cadence Microlensing Field
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We report the discovery of a super-Jovian planet in the microlensing event KMT-2016-BLG-1836, which was found by the Korea Microlensing Telescope Networks high-cadence observations (Gamma ~ 4~{hr}^{-1}). The planet-host mass ratio q ~ 0.004. A Bayesian analysis indicates that the planetary system is composed of a super-Jovian M_{planet} = 2.2_{-1.1}^{+1.9} M_{J} planet orbiting an M or K dwarf M_{rm host} = 0.49_{-0.25}^{+0.38} M_{Sun}, at a distance of D_{L} = 7.1_{-2.4}^{+0.8} kpc. The projected planet-host separation is 3.5^{+1.1}_{-0.9} AU, implying that the planet is located beyond the snowline of the host star. Future high-resolution images can potentially strongly constrain the lens brightness and thus the mass and distance of the planetary system. Without considering detailed detection efficiency, selection or publication biases, we find a potential mass ratio desert at -3.7 lesssim log q lesssim -3.0 for the 31 published KMTNet planets.
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KMT-2016-BLG-2605, with planet-host mass ratio $q=0.012pm 0.001$, has the shortest Einstein timescale, $t_e = 3.41pm 0.13,$days, of any planetary microlensing event to date. This prompts us to examine the full sample of 7 short ($t_e<7,$day) planetary events with good $q$ measurements. We find that six have clustered Einstein radii $theta_e = 115pm 20,muas$ and lens-source relative proper motions $mu_relsimeq 9.5pm 2.5,masyr$. For the seventh, these two quantities could not be measured. These distributions are consistent with a Galactic-bulge population of very low-mass (VLM) hosts near the hydrogen-burning limit. This conjecture could be verified by imaging at first adaptive-optics light on next-generation (30m) telescopes. Based on a preliminary assessment of the sample, planetary companions (i.e., below the deuterium-burning limit) are divided into genuine planets, formed in their disks by core accretion, and very low-mass brown dwarfs, which form like stars. We discuss techniques for expanding the sample, which include taking account of the peculiar anomaly dominated morphology of the KMT-2016-BLG-2605 light curve.
We report the discovery of KMT-2018-BLG-1292Lb, a super-Jovian $M_{rm planet} = 4.5pm 1.3,M_J$ planet orbiting an F or G dwarf $M_{rm host} = 1.5pm 0.4,M_odot$, which lies physically within ${cal O}(10,pc)$ of the Galactic plane. The source star is a heavily extincted $A_Isim 5.2$ luminous giant that has the lowest Galactic latitude, $b=-0.28^circ$, of any planetary microlensing event. The relatively blue blended light is almost certainly either the host or its binary companion, with the first explanation being substantially more likely. This blend dominates the light at $I$ band and completely dominates at $R$ and $V$ bands. Hence, the lens system can be probed by follow-up observations immediately, i.e., long before the lens system and the source separate due to their relative proper motion. The system is well characterized despite the low cadence $Gamma=0.15$--$0.20,{rm hr^{-1}}$ of observations and short viewing windows near the end of the bulge season. This suggests that optical microlensing planet searches can be extended to the Galactic plane at relatively modest cost.
We aim to find missing microlensing planets hidden in the unanalyzed lensing events of previous survey data. For this purpose, we conduct a systematic inspection of high-magnification microlensing events, with peak magnifications $A_{rm peak}gtrsim 30$, in the data collected from high-cadence surveys in and before the 2018 season. From this investigation, we identify an anomaly in the lensing light curve of the event KMT-2018-BLG-1025. The analysis of the light curve indicates that the anomaly is caused by a very low mass-ratio companion to the lens. We identify three degenerate solutions, in which the ambiguity between a pair of solutions (solutions B) is caused by the previously known close--wide degeneracy, and the degeneracy between these and the other solution (solution A) is a new type that has not been reported before. The estimated mass ratio between the planet and host is $qsim 0.8times 10^{-4}$ for the solution A and $qsim 1.6times 10^{-4}$ for the solutions B. From the Bayesian analysis conducted with measured observables, we estimate that the masses of the planet and host and the distance to the lens are $(M_{rm p}, M_{rm h}, D_{rm L})sim (6.1~M_oplus, 0.22~M_odot, 6.7~{rm kpc})$ for the solution A and $sim (4.4~M_oplus, 0.08~M_odot, 7.5~{rm kpc})$ for the solutions B. The planet mass is in the category of a super-Earth regardless of the solutions, making the planet the eleventh super-Earth planet, with masses lying between those of Earth and the Solar systems ice giants, discovered by microlensing.
We report the discovery of an extrasolar planet detected from the combined data of a microlensing event OGLE-2015-BLG-0051/KMT-2015-BLG-0048 acquired by two microlensing surveys. Despite that the short planetary signal occurred in the very early Bulge season during which the lensing event could be seen for just about an hour, the signal was continuously and densely covered. From the Bayesian analysis using models of the mass function, matter and velocity distributions combined with the information of the angular Einstein radius, it is found that the host of the planet is located in the Galactic bulge. The planet has a mass $0.72_{-0.07}^{+0.65} M_{rm J}$ and it is orbiting a low-mass M-dwarf host with a projected separation $d_perp=0.73 pm 0.08$ AU. The discovery of the planet demonstrates the capability of the current high-cadence microlensing lensing surveys in detecting and characterizing planets.
We show that microlensing event KMT-2016-BLG-1107 displays a new type of degeneracy between wide-binary and close-binary Hollywood events in which a giant-star source envelops the planetary caustic. The planetary anomaly takes the form of a smooth, two-day bump far out on the falling wing of the light curve, which can be interpreted either as the source completely enveloping a minor-image caustic due to a close companion with mass ratio $q=0.036$, or partially enveloping a major-image caustic due to a wide companion with $q=0.004$. The best estimates of the companion masses are both in the planetary regime ($3.3^{+3.5}_{-1.8},M_{rm jup}$ and $0.090^{+0.096}_{-0.037},M_{rm jup}$) but differ by an even larger factor than the mass ratios due to different inferred host masses. We show that the two solutions can be distinguished by high-resolution imaging at first light on next-generation (30m) telescopes. We provide analytic guidance to understand the conditions under which this new type of degeneracy can appear.
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