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Register a new userOGLE-2018-BLG-0532Lb: Cold Neptune With Possible Jovian Sibling
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We report the discovery of the planet OGLE-2018-BLG-0532Lb, with very obvious signatures in the light curve that lead to an estimate of the planet-host mass ratio $q=M_{rm planet}/M_{rm host}simeq 1times10^{-4}$. Although there are no obvious systematic residuals to this double-lens/single-source (2L1S) fit, we find that $chi^2$ can be significantly improved by adding either a third lens (3L1S, $Deltachi^2=81$) or second source (2L2S, $Deltachi^2=65$) to the lens-source geometry. After thorough investigation, we conclude that we cannot decisively distinguish between these two scenarios and therefore focus on the robustly-detected planet. However, given the possible presence of a second planet, we investigate to what degree and with what probability such additional planets may affect seemingly single-planet light curves. Our best estimates for the properties of the lens star and the secure planet are: a host mass $Msim 0.25,M_odot$, system distance $D_Lsim 1,$kpc and planet mass $m_{p,1}= 8,M_oplus$ with projected separation $a_{1,perp}=1.4,$au. However, there is a relatively bright $I=18.6$ (and also relatively blue) star projected within $<50,$mas of the lens, and if future high-resolution images show that this is coincident with the lens, then it is possible that it is the lens, in which case, the lens would be both more massive and more distant than the best-estimated values above.
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We present the discovery of a Neptune-mass planet OGLE-2007-BLG-368Lb with a planet-star mass ratio of q=[9.5 +/- 2.1] x 10^{-5} via gravitational microlensing. The planetary deviation was detected in real-time thanks to the high cadence of the MOA survey, real-time light curve monitoring and intensive follow-up observations. A Bayesian analysis returns the stellar mass and distance at M_l = 0.64_{-0.26}^{+0.21} M_sun and D_l = 5.9_{-1.4}^{+0.9} kpc, respectively, so the mass and separation of the planet are M_p = 20_{-8}^{+7} M_oplus and a = 3.3_{-0.8}^{+1.4} AU, respectively. This discovery adds another cold Neptune-mass planet to the planetary sample discovered by microlensing, which now comprise four cold Neptune/Super-Earths, five gas giant planets, and another sub-Saturn mass planet whose nature is unclear. The discovery of these ten cold exoplanets by the microlensing method implies that the mass ratio function of cold exoplanets scales as dN_{rm pl}/dlog q propto q^{-0.7 +/- 0.2} with a 95% confidence level upper limit of n < -0.35 (where dN_{rm pl}/dlog q propto q^n). As microlensing is most sensitive to planets beyond the snow-line, this implies that Neptune-mass planets are at least three times more common than Jupiters in this region at the 95% confidence level.
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 the microlensing event OGLE-2018-BLG-1269, with planet-host mass ratio $q sim 6times10^{-4}$, i.e., $0.6$ times smaller than the Jupiter/Sun mass ratio. Combined with the $Gaia$ parallax and proper motion, a strong one-dimensional constraint on the microlens parallax vector allows us to significantly reduce the uncertainties of lens physical parameters. A Bayesian analysis that ignores any information about light from the host yields that the planet is a cold giant $(M_{2} = 0.69_{-0.22}^{+0.44},M_{rm J})$ orbiting a Sun-like star $(M_{1} = 1.13_{-0.35}^{+0.72},M_{odot})$ at a distance of $D_{rm L} = 2.56_{-0.62}^{+0.92},{rm kpc}$. The projected planet-host separation is $a_{perp} = 4.61_{-1.17}^{+1.70},{rm au}$. Using {it Gaia} astrometry, we show that the blended light lies $lesssim 12,$mas from the host and therefore must be either the host star or a stellar companion to the host. An isochrone analysis favors the former possibility at $>99.6%$. The host is therefore a subgiant. For host metallicities in the range of $0.0 leq {rm [Fe/H]} leq +0.3$, the host and planet masses are then in the range of $1.16 leq M_{1}/M_{odot} leq 1.38$ and $0.74 leq M_{2}/M_{rm J} leq 0.89$, respectively. Low host metallicities are excluded. The brightness and proximity of the lens make the event a strong candidate for spectroscopic followup both to test the microlensing solution and to further characterize the system.
We report the detection of a Cold Neptune m_planet=21+/-2MEarth orbiting a 0.38MSol M dwarf lying 2.5-3.3 kpc toward the Galactic center as part of a campaign combining ground-based and Spitzer observations to measure the Galactic distribution of planets. This is the first time that the complex real-time protocols described by Yee et al. (2015), which aim to maximize planet sensitivity while maintaining sample integrity, have been carried out in practice. Multiple survey and follow-up teams successfully combined their efforts within the framework of these protocols to detect this planet. This is the second planet in the Spitzer Galactic distribution sample. Both are in the near-to-mid disk and clearly not in the Galactic bulge.
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.
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