32 research outputs found

    The First Neptune Analog or Super-Earth with Neptune-like Orbit: MOA-2013-BLG-605Lb

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    We present the discovery of the first Neptune analog exoplanet or super-Earth with Neptune-like orbit, MOA-2013-BLG-605Lb. This planet has a mass similar to that of Neptune or a super-Earth and it orbits at 9149\sim 14 times the expected position of the snow-line, asnowa_{\rm snow}, which is similar to Neptune's separation of 11asnow 11\,a_{\rm snow} from the Sun. The planet/host-star mass ratio is q=(3.6±0.7)×104q=(3.6\pm0.7)\times 10^{-4} and the projected separation normalized by the Einstein radius is s=2.39±0.05s=2.39\pm0.05. There are three degenerate physical solutions and two of these are due to a new type of degeneracy in the microlensing parallax parameters, which we designate "the wide degeneracy". The three models have (i) a Neptune-mass planet with a mass of Mp=217+6MEarthM_{\rm p}=21_{-7}^{+6} M_{Earth} orbiting a low-mass M-dwarf with a mass of Mh=0.190.06+0.05MM_{\rm h}=0.19_{-0.06}^{+0.05} M_\odot, (ii) a mini-Neptune with Mp=7.91.2+1.8MEarthM_{\rm p}= 7.9_{-1.2}^{+1.8} M_{Earth} orbiting a brown dwarf host with Mh=0.0680.011+0.019MM_{\rm h}=0.068_{-0.011}^{+0.019} M_\odot and (iii) a super-Earth with Mp=3.20.3+0.5MEarthM_{\rm p}= 3.2_{-0.3}^{+0.5} M_{Earth} orbiting a low-mass brown dwarf host with Mh=0.0250.004+0.005MM_{\rm h}=0.025_{-0.004}^{+0.005} M_\odot which is slightly favored. The 3-D planet-host separations are 4.61.2+4.7_{-1.2}^{+4.7} AU, 2.10.2+1.0_{-0.2}^{+1.0} AU and 0.940.02+0.67_{-0.02}^{+0.67} AU, which are 8.91.4+10.58.9_{-1.4}^{+10.5}, 121+712_{-1}^{+7} or 141+1114_{-1}^{+11} times larger than asnowa_{\rm snow} for these models, respectively. The Keck AO observation confirm that the lens is faint. This discovery suggests that low-mass planets with Neptune-like orbit are common. So processes similar to the one that formed Neptune in our own Solar System or cold super-Earth may be common in other solar systems.Comment: 54 pages, 10 figures, 13 tables, Accepted for publication in the Ap

    The first circumbinary planet found by microlensing: OGLE-2007-BLG-349L(AB)c

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    We present the analysis of the first circumbinary planet microlensing event, OGLE-2007-BLG-349. This event has a strong planetary signal that is best fit with a mass ratio of q ≈ 3.4 × 10-4, but there is an additional signal due to an additional lens mass, either another planet or another star. We find acceptable light-curve fits with two classes of models: two-planet models (with a single host star) and circumbinary planet models. The light curve also reveals a significant microlensing parallax effect, which constrains the mass of the lens system to be M L ≈ 0.7 M⊙. Hubble Space Telescope (HST) images resolve the lens and source stars from their neighbors and indicate excess flux due to the star(s) in the lens system. This is consistent with the predicted flux from the circumbinary models, where the lens mass is shared between two stars, but there is not enough flux to be consistent with the two-planet, one-star models. So, only the circumbinary models are consistent with the HST data. They indicate a planet of mass m c = 80 ± 13 M⊙, orbiting a pair of M dwarfs with masses of M A = 0.41 ± 0.07 and M B = 0.30 ± 0.07, which makes this the lowest-mass circumbinary planet system known. The ratio of the separation between the planet and the center of mass to the separation of the two stars is ∼40, so unlike most of the circumbinary planets found by Kepler, the planet does not orbit near the stability limit

    Faint source star planetary microlensing : the discovery of the cold gas giant planet OGLE-2014-BLG-0676Lb

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    We report the discovery of a planet — OGLE-2014-BLG-0676Lb— via gravitational microlensing. Observations for the lensing event were made by the MOA, OGLE, Wise, RoboNET/LCOGT, MiNDSTEp and μFUN groups. All analyses of the light curve data favour a lens system comprising a planetary mass orbiting a host star. The most favoured binary lens model has a mass ratio between the two lens masses of (4.78 ± 0.13) × 10−3. Subject to some important assumptions, a Bayesian probability density analysis suggests the lens system comprises a 3.09 (+1.02/−1.12) MJ planet orbiting a 0.62(+0.20/−0.22) M⊙ host star at a deprojected orbital separation of 4.40 (+2.16/−1.46) AU. The distance to the lens system is 2.22 (+0.96/−0.83) kpc. Planet OGLE-2014-BLG-0676Lb provides additional data to the growing number of cool planets discovered using gravitational microlensing against which planetary formation theories may be tested. Most of the light in the baseline of this event is expected to come from the lens and thus high-resolution imaging observations could confirm our planetary model interpretation.PostprintPeer reviewe

    Spitzer Observations Of Ogle-2015-blg-1212 Reveal A New Path Toward Breaking Strong Microlens Degeneracies

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    Spitzer microlensing parallax observations of OGLE-2015-BLG-1212 decisively break a degeneracy between planetary and binary solutions that is somewhat ambiguous when only ground-based data are considered. Only eight viable models survive out of an initial set of 32 local minima in the parameter space. These models clearly indicate that the lens is a stellar binary system possibly located within the bulge of our Galaxy, ruling out the planetary alternative. We argue that several types of discrete degeneracies can be broken via such space-based parallax observations

    Faint-source-star planetary microlensing: the discovery of the cold gas-giant planet OGLE-2014-BLG-0676Lb

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    We report the discovery of a planet – OGLE-2014-BLG-0676Lb– via gravitational microlensing. Observations for the lensing event were made by the following groups: Microlensing Observations in Astrophysics; Optical Gravitational Lensing Experiment; Wise Observatory; RoboNET/Las Cumbres Observatory Global Telescope; Microlensing Network for the Detection of Small Terrestrial Exoplanets; and μ-FUN. All analyses of the light-curve data favour a lens system comprising a planetary mass orbiting a host star. The most-favoured binary lens model has a mass ratio between the two lens masses of (4.78 ± 0.13) × 10−3. Subject to some important assumptions, a Bayesian probability density analysis suggests the lens system comprises a 3.09+1.02 −1.12 MJ planet orbiting a 0.62+0.20 −0.22 M host star at a deprojected orbital separation of 4.40+2.16 −1.46 au. The distance to the lens system is 2.22+0.96 −0.83 kpc. Planet OGLE- 2014-BLG-0676Lb provides additional data to the growing number of cool planets discovered using gravitational microlensing against which planetary formation theories may be tested. Most of the light in the baseline of this event is expected to come from the lens and thus high-resolution imaging observations could confirm our planetary model interpretation

    The First Simultaneous Microlensing Observations by Two Space Telescopes: <i>Spitzer</i> and <i>Swift</i> Reveal a Brown Dwarf in Event OGLE-2015-BLG-1319

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    Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by directly measuring the “microlens parallax.” We report the discovery of a 30–65MJ brown dwarf orbiting a K dwarf in the microlensing event OGLE-2015-BLG-1319. The system is located at a distance of ∼5 kpc toward the Galactic Bulge. The event was observed by several ground-based groups as well as by Spitzer and Swift, allowing a measurement of the physical properties. However, the event is still subject to an eight-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either ∼0.25 au or ∼45 au. This is the first microlensing event observed by Swift, with the UVOT camera. We study the region of microlensing parameter space to which Swift is sensitive, finding that though Swift could not measure the microlens parallax with respect to ground-based observations for this event, it can be important for other events. Specifically, it is important for detecting nearby brown dwarfs and free-floating planets in high magnification events

    Spitzer Parallax Of Ogle-2015-blg-0966: A Cold Neptune In The Galactic Disk

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    We report the detection of a cold Neptune mplanet = 21 ± 2 M? orbiting a 0.38 M? 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., 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 are clearly not in the Galactic bulge
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