202 research outputs found

    OGLE-2016-BLG-1227L: A Wide-separation Planet from a Very Short-timescale Microlensing Event

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    We present the analysis of the microlensing event OGLE-2016-BLG-1227. The light curve of this short-duration event appears to be a single-lens event affected by severe finite-source effects. Analysis of the light curve based on single-lens single-source (1L1S) modeling yields very small values of the event timescale, t_E ∌ 3.5 days, and the angular Einstein radius, Ξ_E ∌ 0.009 mas, making the lens a candidate of a free-floating planet. Close inspection reveals that the 1L1S solution leaves small residuals with amplitude ΔI â‰Č 0.03 mag. We find that the residuals are explained by the existence of an additional widely-separated heavier lens component, indicating that the lens is a wide-separation planetary system rather than a free-floating planet. From Bayesian analysis, it is estimated that the planet has a mass of _p = 0.79^(+1.30)_(−0.39) M_J and it is orbiting a low-mass host star with a mass of M_(host) = 0.10+0.17−0.05 M_⊙ located with a projected separation of a_ = 3.4^(+2.1)_(−1.0) au. The planetary system is located in the Galactic bulge with a line-of-sight separation from the source star of D_(LS) = 1.21^(+0.96)_(−0.63) kpc. The event shows that there are a range of deviations in the signatures of host stars for apparently isolated planetary lensing events and that it is possible to identify a host even when a deviation is subtle

    KMT-2018-BLG-1292: A Super-Jovian Microlens Planet in the Galactic Plane

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    We report the discovery of KMT-2018-BLG-1292Lb, a super-Jovian Mplanet=4.5±1.3 MJM_{\rm planet} = 4.5\pm 1.3\,M_J planet orbiting an F or G dwarf Mhost=1.5±0.4 M⊙M_{\rm host} = 1.5\pm 0.4\,M_\odot, which lies physically within {\cal O}(10\,\pc) of the Galactic plane. The source star is a heavily extincted AI∌5.2A_I\sim 5.2 luminous giant that has the lowest Galactic latitude, b=−0.28∘b=-0.28^\circ, of any planetary microlensing event. The relatively blue blended light is almost certainly either the host or its binary companion, with the first explanation being substantially more likely. This blend dominates the light at II band and completely dominates at RR and VV bands. Hence, the lens system can be probed by follow-up observations immediately, i.e., long before the lens system and the source separate due to their relative proper motion. The system is well characterized despite the low cadence Γ=0.15\Gamma=0.15--0.20 hr−10.20\,{\rm hr^{-1}} of observations and short viewing windows near the end of the bulge season. This suggests that optical microlensing planet searches can be extended to the Galactic plane at relatively modest cost.Comment: 35 pages, 3 Tables, 8 figure

    OGLE-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=Mplanet/Mhost≃1×10−4q=M_{\rm planet}/M_{\rm host}\simeq 1\times10^{-4}. Although there are no obvious systematic residuals to this double-lens/single-source (2L1S) fit, we find that χ2\chi^2 can be significantly improved by adding either a third lens (3L1S, Δχ2=81\Delta\chi^2=81) or second source (2L2S, Δχ2=65\Delta\chi^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 M∌0.25 M⊙M\sim 0.25\,M_\odot, system distance DL∌1 D_L\sim 1\,kpc and planet mass mp,1=8 M⊕m_{p,1}= 8\,M_\oplus with projected separation a1,⊄=1.4 a_{1,\perp}=1.4\,au. However, there is a relatively bright I=18.6I=18.6 (and also relatively blue) star projected within <50 <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.Comment: 48 pages, 9 figures, 7 table

    A noncanonical role for the engulfment gene ELMO1 in neutrophils that promotes inflammatory arthritis

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    Rheumatoid arthritis is characterized by progressive joint inflammation and affects similar to 1% of the human population. We noted single-nucleotide polymorphisms (SNPs) in the apoptotic cell-engulfment genes ELMO1, DOCK2, and RAC1 linked to rheumatoid arthritis. As ELMO1 promotes cytoskeletal reorganization during engulfment, we hypothesized that ELMO1 loss would worsen inflammatory arthritis. Surprisingly, Elmo1-deficient mice showed reduced joint inflammation in acute and chronic arthritis models. Genetic and cell-biology studies revealed that ELMO1 associates with receptors linked to neutrophil function in arthritis and regulates activation and early neutrophil recruitment to the joints, without general inhibition of inflammatory responses. Further, neutrophils from the peripheral blood of human donors that carry the SNP in ELMO1 associated with arthritis display increased migratory capacity, whereas ELMO1 knockdown reduces human neutrophil migration to chemokines linked to arthritis. These data identify 'noncanonical' roles for ELMO1 as an important cytoplasmic regulator of specific neutrophil receptors and promoter of arthritis

    Spectroscopic Mass and Host-star Metallicity Measurements for Newly Discovered Microlensing Planet OGLE-2018-BLG-0740Lb

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    We report the discovery of the microlensing planet OGLE-2018-BLG-0740Lb. The planet is detected with a very strong signal of Δχ2∌4630\Delta\chi^2\sim 4630, but the interpretation of the signal suffers from two types of degeneracies. One type is caused by the previously known close/wide degeneracy, and the other is caused by an ambiguity between two solutions, in which one solution requires to incorporate finite-source effects, while the other solution is consistent with a point-source interpretation. Although difficult to be firmly resolved based on only the photometric data, the degeneracy is resolved in strong favor of the point-source solution with the additional external information obtained from astrometric and spectroscopic observations. The small astrometric offset between the source and baseline object supports that the blend is the lens and this interpretation is further secured by the consistency of the spectroscopic distance estimate of the blend with the lensing parameters of the point-source solution. The estimated mass of the host is 1.0±0.1 M⊙1.0\pm 0.1~M_\odot and the mass of the planet is 4.5±0.6 MJ4.5\pm 0.6~M_{\rm J} (close solution) or 4.8±0.6 MJ4.8\pm 0.6~M_{\rm J} (wide solution) and the lens is located at a distance of 3.2±0.53.2\pm 0.5~kpc. The bright nature of the lens, with I∌17.1I\sim 17.1 (V∌18.2V\sim 18.2), combined with its dominance of the observed flux suggest that radial-velocity (RV) follow-up observations of the lens can be done using high-resolution spectrometers mounted on large telescopes, e.g., VLT/ESPRESSO, and this can potentially not only measure the period and eccentricity of the planet but also probe for close-in planets. We estimate that the expected RV amplitude would be ∌60sin⁥i m s−1\sim 60\sin i ~{\rm m~s}^{-1}.Comment: 12 pages, 11 figures, 4 table

    OGLE-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 M1=0.40±0.05 M⊙M_1=0.40 \pm 0.05~M_\odot and M2=0.13±0.01 M⊙M_2=0.13\pm 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.Comment: 10 pages, 10 figures, 4 table
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