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Register a new userOGLE-2018-BLG-0022: First Prediction of an Astrometric Microlensing Signal from a Photometric Microlensing Event
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In this work, we present the analysis of the binary microlensing event OGLE-2018-BLG-0022 that is detected toward the Galactic bulge field. The dense and continuous coverage with the high-quality photometry data from ground-based observations combined with the space-based {it Spitzer} observations of this long time-scale event enables us to uniquely determine the masses $M_1=0.40 pm 0.05~M_odot$ and $M_2=0.13pm 0.01~M_odot$ of the individual lens components. Because the lens-source relative parallax and the vector lens-source relative proper motion are unambiguously determined, we can likewise unambiguously predict the astrometric offset between the light centroid of the magnified images (as observed by the {it Gaia} satellite) and the true position of the source. This prediction can be tested when the individual-epoch {it Gaia} astrometric measurements are released.
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We present the analysis of stellar binary microlensing event OGLE-2015-BLG-0060 based on observations obtained from 13 different telescopes. Intensive coverage of the anomalous parts of the light curve was achieved by automated follow-up observations from the robotic telescopes of the Las Cumbres Observatory. We show that, for the first time, all main features of an anomalous microlensing event are well covered by follow-up data, allowing us to estimate the physical parameters of the lens. The strong detection of second-order effects in the event light curve necessitates the inclusion of longer-baseline survey data in order to constrain the parallax vector. We find that the event was most likely caused by a stellar binary-lens with masses $M_{star1} = 0.87 pm 0.12 M_{odot}$ and $M_{star2} = 0.77 pm 0.11 M_{odot}$. The distance to the lensing system is 6.41 $pm 0.14$ kpc and the projected separation between the two components is 13.85 $pm 0.16$ AU. Alternative interpretations are also considered.
We present the analyses of two microlensing events, OGLE-2018-BLG-0567 and OGLE-2018-BLG-0962. In both events, the short-lasting anomalies were densely and continuously covered by two high-cadence surveys. The light-curve modeling indicates that the anomalies are generated by source crossings over the planetary caustics induced by planetary companions to the hosts. The estimated planet/host separation (scaled to the angular Einstein radius $theta_{rm E}$) and mass ratio are $(s, q) = (1.81, 1.24times10^{-3})$ and $(s, q) = (1.25, 2.38times10^{-3})$, respectively. From Bayesian analyses, we estimate the host and planet masses as $(M_{rm h}, M_{rm p}) = (0.24_{-0.13}^{+0.16},M_{odot}, 0.32_{-0.16}^{+0.34},M_{rm J})$ and $(M_{rm h}, M_{rm p}) = (0.55_{-0.29}^{+0.32},M_{odot}, 1.37_{-0.72}^{+0.80},M_{rm J})$, respectively. These planetary systems are located at a distance of $7.07_{-1.15}^{+0.93},{rm kpc}$ for OGLE-2018-BLG-0567 and $6.47_{-1.73}^{+1.04},{rm kpc}$ for OGLE-2018-BLG-0962, suggesting that they are likely to be near the Galactic bulge. The two events prove the capability of current high-cadence surveys for finding planets through the planetary-caustic channel. We find that most published planetary-caustic planets are found in Hollywood events in which the source size strongly contributes to the anomaly cross section relative to the size of the caustic.
We report the discovery of a planet in a binary that was discovered from the analysis of the microlensing event OGLE-2018-BLG-1700. We identify the triple nature of the lens from the fact that the complex anomaly pattern can be decomposed into two parts produced by two binary-lens events, in which one binary pair has a very low mass ratio of $sim 0.01$ between the lens components and the other pair has a mass ratio of $sim 0.3$. We find two sets of degenerate solutions, in which one solution has a projected separation between the primary and its stellar companion less than the angular Einstein radius $thetae$ (close solution), while the other solution has a separation greater than $thetae$ (wide solution). From the Bayesian analysis with the constraints of the event time scale and angular Einstein radius together with the location of the source lying in the far disk behind the bulge, we find that the planet is a super-Jupiter with a mass of $4.4^{+3.0}_{-2.0}~M_{rm J}$ and the stellar binary components are early and late M-type dwarfs with masses $0.42^{+0.29}_{-0.19}~M_odot$ and $0.12^{+0.08}_{-0.05}~M_odot$, respectively, and the planetary system is located at a distance of $D_{rm L}=7.6^{+1.2}_{-0.9}~{rm kpc}$. The planet is a circumstellar planet according to the wide solution, while it is a circumbinary planet according to the close solution. The projected primary-planet separation is $2.8^{+3.2}_{-2.5}~{rm au}$ commonly for the close and wide solutions, but the primary-secondary binary separation of the close solution, $0.75^{+0.87}_{-0.66}~{rm au}$, is widely different from the separation, $10.5^{+12.1}_{-9.2}~{rm au}$, of the wide solution.
We report observations of the binary microlensing event OGLE-2018-BLG-0022, provided by the ROME/REA Survey, which indicate that the lens is a low-mass binary star consisting of M3 (0.375+/-0.020 Msun) and M7 (0.098+/-0.005 Msun) components. The lens is unusually close, at 0.998+/-0.047 kpc, compared with the majority of microlensing events, and despite its intrinsically low luminosity, it is likely that AO observations in the near future will be able to provide an independent confirmation of the lens masses.
We present the analysis of the binary-microlensing event OGLE-2014-BLG-0289. The event light curve exhibits very unusual five peaks where four peaks were produced by caustic crossings and the other peak was produced by a cusp approach. It is found that the quintuple-peak features of the light curve provide tight constraints on the source trajectory, enabling us to precisely and accurately measure the microlensing parallax $pi_{rm E}$. Furthermore, the three resolved caustics allow us to measure the angular Einstein radius $thetae$. From the combination of $pi_{rm E}$ and $thetae$, the physical lens parameters are uniquely determined. It is found that the lens is a binary composed of two M dwarfs with masses $M_1 = 0.52 pm 0.04 M_odot$ and $M_2=0.42 pm 0.03 M_odot$ separated in projection by $a_perp = 6.4 pm 0.5$ au. The lens is located in the disk with a distance of $D_{rm L} = 3.3 pm 0.3$~kpc. It turns out that the reason for the absence of a lensing signal in the {it Spitzer} data is that the time of observation corresponds to the flat region of the light curve.
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