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Register a new userOGLE-2012-BLG-0563Lb: a Saturn-mass Planet around an M Dwarf with the Mass Constrained by Subaru AO imaging
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We report the discovery of a microlensing exoplanet OGLE-2012-BLG-0563Lb with the planet-star mass ratio ~1 x 10^{-3}. Intensive photometric observations of a high-magnification microlensing event allow us to detect a clear signal of the planet. Although no parallax signal is detected in the light curve, we instead succeed at detecting the flux from the host star in high-resolution JHK-band images obtained by the Subaru/AO188 and IRCS instruments, allowing us to constrain the absolute physical parameters of the planetary system. With the help of a spectroscopic information about the source star obtained during the high-magnification state by Bensby et al., we find that the lens system is located at 1.3^{+0.6}_{-0.8} kpc from us, and consists of an M dwarf (0.34^{+0.12}_{-0.20} M_sun) orbited by a Saturn-mass planet (0.39^{+0.14}_{-0.23} M_Jup) at the projected separation of 0.74^{+0.26}_{-0.42} AU (close model) or 4.3^{+1.5}_{-2.5} AU (wide model). The probability of contamination in the host stars flux, which would reduce the masses by a factor of up to three, is estimated to be 17%. This possibility can be tested by future high-resolution imaging. We also estimate the (J-Ks) and (H-Ks) colors of the host star, which are marginally consistent with a low metallicity mid-to-early M dwarf, although further observations are required for the metallicity to be conclusive. This is the fifth sub-Jupiter-mass (0.2<m_p/M_Jup<1) microlensing planet around an M dwarf with the mass well constrained. The relatively rich harvest of sub-Jupiters around M dwarfs is contrasted with a possible paucity of ~1--2 Jupiter-mass planets around the same type of star, which can be explained by the planetary formation process in the core-accretion scheme.
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We report the discovery of a planet by the microlensing method, OGLE-2012-BLG-0724Lb. Although the duration of the planetary signal for this event was one of the shortest seen for a planetary event, the anomaly was well covered thanks to high cadence observations taken by the survey groups OGLE and MOA. By analyzing the light curve, this planetary system is found to have a mass ratio $q=(1.58pm0.15)times10^{-3}$. By conducting a Bayesian analysis, we estimate that the host star is an M-dwarf star with a mass of $M_{rm L}=0.29_{-0.16}^{+0.33} M_{odot}$ located at $D_{rm L}=6.7_{-1.2}^{+1.1} {rm kpc}$ away from the Earth and the companions mass is $m_{rm P}=0.47_{-0.26}^{+0.54} M_{rm Jup}$. The projected planet-host separation is $a_{perp}=1.6_{-0.3}^{+0.4} {rm AU}$. Because the lens-source relative proper motion is relatively high, future high resolution images would detect the lens host star and determine the lens properties uniquely. This system is likely a Saturn-mass exoplanet around an M-dwarf and such systems are commonly detected by gravitational microlensing. This adds an another example of a possible pileup of sub-Jupiters $(0.2 < m_{rm P}/M_{rm Jup} < 1)$ in contrast to a lack of Jupiters ($sim 1 - 2 M_{rm Jup}$) around M-dwarfs, supporting the prediction by core accretion models that Jupiter-mass or more massive planets are unlikely to form around M-dwarfs.
We report the discovery of a $Spitzer$ microlensing planet OGLE-2018-BLG-0596Lb, with preferred planet-host mass ratio $q sim 2times10^{-4}$. The planetary signal, which is characterized by a short $(sim 1~{rm day})$ bump on the rising side of the lensing light curve, was densely covered by ground-based surveys. We find that the signal can be explained by a bright source that fully envelops the planetary caustic, i.e., a Hollywood geometry. Combined with the source proper motion measured from $Gaia$, the $Spitzer$ satellite parallax measurement makes it possible to precisely constrain the lens physical parameters. The preferred solution, in which the planet perturbs the minor image due to lensing by the host, yields a Uranus-mass planet with a mass of $M_{rm p} = 13.9pm1.6~M_{oplus}$ orbiting a mid M-dwarf with a mass of $M_{rm h} = 0.23pm0.03~M_{odot}$. There is also a second possible solution that is substantially disfavored but cannot be ruled out, for which the planet perturbs the major image. The latter solution yields $M_{rm p} = 1.2pm0.2~M_{oplus}$ and $M_{rm h} = 0.15pm0.02~M_{odot}$. By combining the microlensing and $Gaia$ data together with a Galactic model, we find in either case that the lens lies on the near side of the Galactic bulge at a distance $D_{rm L} sim 6pm1~{rm kpc}$. Future adaptive optics observations may decisively resolve the major image/minor image degeneracy.
We report the discovery and analysis of a sub-Saturn-mass planet in the microlensing event OGLE-2018-BLG-0799. The planetary signal was observed by several ground-based telescopes, and the planet-host mass ratio is $q = (2.65 pm 0.16) times 10^{-3}$. The ground-based observations yield a constraint on the angular Einstein radius $theta_{rm E}$, and the microlens parallax $pi_{rm E}$ is measured from the joint analysis of the Spitzer and ground-based observations, which suggests that the host star is most likely to be a very low-mass dwarf. A full Bayesian analysis using a Galactic model indicates that the planetary system is composed of an $M_{rm planet} = 0.22_{-0.06}^{+0.19}~M_{J}$ planet orbiting an $M_{rm host} = 0.080_{-0.020}^{+0.080}~M_odot$, at a distance of $D_{rm L} = 4.42_{-1.23}^{+1.73}$ kpc. The projected planet-host separation is $r_perp = 1.27_{-0.29}^{+0.45}$ AU, implying that the planet is located beyond the snowline of the host star. However, because of systematics in the Spitzer photometry, there is ambiguity in the parallax measurement, so the system could be more massive and farther away.
We report the discovery and the analysis of the planetary microlensing event, OGLE-2013-BLG-1761. There are some degenerate solutions in this event because the planetary anomaly is only sparsely sampled. But the detailed light curve analysis ruled out all stellar binary models and shows that the lens to be a planetary system. There is the so-called close/wide degeneracy in the solutions with the planet/host mass ratio of $q sim (7.5 pm 1.5) times 10^{-3}$ and $q sim (9.3 pm 2.9) times 10^{-3}$ with the projected separation in Einstein radius units of $s = 0.95$ (close) and $s = 1.19$ (wide), respectively. The microlens parallax effect is not detected but the finite source effect is detected. Our Bayesian analysis indicates that the lens system is located at $D_{rm L}=6.9_{-1.2}^{+1.0} {rm kpc}$ away from us and the host star is an M/K-dwarf with the mass of $M_{rm L}=0.33_{-0.18}^{+0.32} M_{odot}$ orbited by a super-Jupiter mass planet with the mass of $m_{rm P}=2.8_{-1.5}^{+2.5} M_{rm Jup}$ at the projected separation of $a_{perp}=1.8_{-0.5}^{+0.5} {rm AU}$. The preference of the large lens distance in the Bayesian analysis is due to the relatively large observed source star radius. The distance and other physical parameters can be constrained by the future high resolution imaging by ground large telescopes or HST. If the estimated lens distance is correct, this planet provides another sample for testing the claimed deficit of planets in the Galactic bulge.
We present the discovery of two planetary systems consisting of a Saturn-mass planet orbiting an M-dwarf, which were detected in faint microlensing events OGLE-2013-BLG-0132 and OGLE-2013-BLG-1721. The planetary anomalies were covered with high cadence by OGLE and MOA photometric surveys. The light curve modeling indicates that the planet-to-host mass ratios are $(5.15 pm 0.28)times 10^{-4}$ and $(13.18 pm 0.72)times 10^{-4}$, respectively. Both events were too short and too faint to measure a reliable parallax signal and hence the lens mass. We therefore used a Bayesian analysis to estimate the masses of both planets: $0.29^{+0.16}_{-0.13} M_{Jup}$ (OGLE-2013-BLG-0132Lb) and $0.64^{+0.35}_{-0.31} M_{Jup}$ (OGLE-2013-BLG-1721Lb). Thanks to a high relative proper motion, OGLE-2013-BLG-0132 is a promising candidate for the high-resolution imaging follow-up. Both planets belong to an increasing sample of sub-Jupiter-mass planets orbiting M-dwarfs beyond the snow line.
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