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Register a new userThe Lowest Mass Ratio Planetary Microlens: OGLE 2016-BLG-1195Lb
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We report discovery of the lowest mass ratio exoplanet to be found by the microlensing method in the light curve of the event OGLE~2016--BLG--1195. This planet revealed itself as a small deviation from a microlensing single lens profile from an examination of the survey data soon after the planetary signal. The duration of the planetary signal is $sim 2.5,$hours. The measured ratio of the planet mass to its host star is $q = 4.2pm 0.7 times10^{-5}$. We further estimate that the lens system is likely to comprise a cold $sim$3 Earth mass planet in a $sim,$2 AU wide orbit around a 0.2 Solar mass star at an overall distance of 7.1 kpc.
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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 a microlensing planet, D_Lens = 0.86 +/- 0.09 kpc. Indeed, it was the large lens-source relative parallax pi_rel=1.0 mas (combined with the low mass M) that gave rise to the large, and thus well-measured, microlens parallax that enabled these precise measurements. OGLE-2017-BLG-1434Lb is the eighth microlensing planet with planet-host mass ratio q < 1 * 10^-4. We apply a new planet-detection sensitivity method, which is a variant of V/V_max, to seven of these eight planets to derive the mass-ratio function in this regime. We find dN/d(ln q) ~ q^p, with p = 1.05 (+0.78,-0.68), which confirms the turnover in the mass function found by Suzuki et al. relative to the power law of opposite sign n = -0.93 +/- 0.13 at higher mass ratios q >~ 2 * 10^-4. We combine our result with that of Suzuki et al. to obtain p = 0.73 (+0.42,-0.34).
We analyze the gravitational binary-lensing event OGLE-2016-BLG-0156, for which the lensing light curve displays pronounced deviations induced by microlens-parallax effects. The light curve exhibits 3 distinctive widely-separated peaks and we find that the multiple-peak feature provides a very tight constraint on the microlens-parallax effect, enabling us to precisely measure the microlens parallax $pi_{rm E}$. All the peaks are densely and continuously covered from high-cadence survey observations using globally located telescopes and the analysis of the peaks leads to the precise measurement of the angular Einstein radius $theta_{rm E}$. From the combination of the measured $pi_{rm E}$ and $theta_{rm E}$, we determine the physical parameters of the lens. It is found that the lens is a binary composed of two M dwarfs with masses $M_1=0.18pm 0.01 M_odot$ and $M_2=0.16pm 0.01 M_odot$ located at a distance $D_{rm L}= 1.35pm 0.09 {rm kpc}$. According to the estimated lens mass and distance, the flux from the lens comprises an important fraction, $sim 25%$, of the blended flux. The bright nature of the lens combined with the high relative lens-source motion, $mu=6.94pm 0.50 {rm mas} {rm yr}^{-1}$, suggests that the lens can be directly observed from future high-resolution follow-up observations.
At $q=1.81pm 0.20 times 10^{-5}$, KMT-2018-BLG-0029Lb has the lowest planet-host mass ratio $q$ of any microlensing planet to date by more than a factor of two. Hence, it is the first planet that probes below the apparent pile-up at $q=5$--10 $times 10^{-5}$. The event was observed by {it Spitzer}, yielding a microlens-parallax $pi_{rm E}$ measurement. Combined with a measurement of the Einstein radius $theta_{rm E}$ from finite-source effects during the caustic crossings, these measurements imply masses of the host $M_{rm host}=1.14^{+0.10}_{-0.12}, M_odot$ and planet $M_{rm planet} = 7.59^{+0.75}_{-0.69},M_oplus$, system distance $D_L = 3.38^{+0.22}_{-0.26},,{rm kpc}$ and projected separation $a_perp = 4.27^{+0.21}_{-0.23},{rm au}$. The blended light, which is substantially brighter than the microlensed source, is plausibly due to the lens and could be observed at high resolution immediately.
We report the discovery and the analysis of the short (tE < 5 days) planetary microlensing event, OGLE-2015-BLG-1771. The event was discovered by the Optical Gravitational Lensing Experiment (OGLE), and the planetary anomaly (at I ~ 19) was captured by The Korea Microlensing Telescope Network (KMTNet). The event has three surviving planetary models that explain the observed light curves, with planet-host mass ratio q ~ 5.4 * 10^{-3}, 4.5 * 10^{-3} and 4.5 * 10^{-2}, respectively. The first model is the best-fit model, while the second model is disfavored by Deltachi^2 ~ 3. The last model is strongly disfavored by Deltachi^2 ~ 15 but not ruled out. A Bayesian analysis using a Galactic model indicates that the first two models are probably composed of a Saturn-mass planet orbiting a late M dwarf, while the third one could consist of a super-Jovian planet and a mid-mass brown dwarf. The source-lens relative proper motion is mu_rel ~ 9 mas/yr, so the source and lens could be resolved by current adaptive-optics (AO) instruments in 2021 if the lens is luminous.
We present an analysis of microlensing event OGLE-2016-BLG-0693, based on the survey-only microlensing observations by the OGLE and KMTNet groups. In order to analyze the light curve, we consider the effects of parallax, orbital motion, and baseline slope, and also refine the result using a Galactic model prior. From the microlensing analysis, we find that the event is a binary composed of a low-mass brown dwarf 49+-20 M_J companion and a K- or G-dwarf host, which lies at a distance 5.0+-0.6 kpc toward the Galactic bulge. The projected separation between the brown dwarf and its host star is less than 5 AU, and thus it is likely that the brown dwarf companion is located in the brown dwarf desert.
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