References of "Monard, L. A. G"
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See detailA Super-Jupiter orbiting a late-type star: A refined analysis of microlensing event OGLE-2012-BLG-0406
Tsapras, Y.; Choi, J.-Y.; Street, R. A. et al

in Astrophysical Journal (2014), 782

We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the lightcurve ... [more ▼]

We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the lightcurve, especially the perturbation part, allowed us to accurately measure the parallax effect and lens orbital motion. Combining our measurement of the lens parallax with the angular Einstein radius determined from finite-source effects, we estimate the physical parameters of the lens system. We find that the event was caused by a $2.73\pm 0.43\ M_{\rm J}$ planet orbiting a $0.44\pm 0.07\ M_{\odot}$ early M-type star. The distance to the lens is $4.97\pm 0.29$\ kpc and the projected separation between the host star and its planet at the time of the event is $3.45\pm 0.26$ AU. We find that the additional coverage provided by follow-up observations, especially during the planetary perturbation, leads to a more accurate determination of the physical parameters of the lens. [less ▲]

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See detailMOA-2010-BLG-311: A planetary candidate below the threshold of reliable detection
Yee, J. C.; Hung, L.-W.; Bond, I. A. et al

in Astrophysical Journal (2013), 769(1), 77

We analyze MOA-2010-BLG-311, a high magnification (A_max>600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a ... [more ▼]

We analyze MOA-2010-BLG-311, a high magnification (A_max>600) microlensing event with complete data coverage over the peak, making it very sensitive to planetary signals. We fit this event with both a point lens and a 2-body lens model and find that the 2-body lens model is a better fit but with only Delta chi^2~140. The preferred mass ratio between the lens star and its companion is $q=10^(-3.7+/-0.1), placing the candidate companion in the planetary regime. Despite the formal significance of the planet, we show that because of systematics in the data the evidence for a planetary companion to the lens is too tenuous to claim a secure detection. When combined with analyses of other high-magnification events, this event helps empirically define the threshold for reliable planet detection in high-magnification events, which remains an open question. [less ▲]

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See detailCharacterizing Lenses and Lensed Stars of High-magnification Single-lens Gravitational Microlensing Events with Lenses Passing over Source Stars
Choi, J.-Y.; Shin, I.-G.; Park, S.-Y. et al

in Astrophysical Journal (2012), 751

We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176 ... [more ▼]

We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all of the events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For seven events, we measure the Einstein radii and the lens-source relative proper motions. Among them, five events are found to have Einstein radii of less than 0.2 mas, making the lenses very low mass star or brown dwarf candidates. For MOA-2011-BLG-274, especially, the small Einstein radius of θ[SUB]E[/SUB] ~ 0.08 mas combined with the short timescale of t [SUB]E[/SUB] ~ 2.7 days suggests the possibility that the lens is a free-floating planet. For MOA-2009-BLG-174, we measure the lens parallax and thus uniquely determine the physical parameters of the lens. We also find that the measured lens mass of ~0.84 M [SUB]&sun;[/SUB] is consistent with that of a star blended with the source, suggesting that the blend is likely to be the lens. Although we did not find planetary signals for any of the events, we provide exclusion diagrams showing the confidence levels excluding the existence of a planet as a function of the separation and mass ratio. [less ▲]

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See detailMicrolensing Binaries Discovered through High-magnification Channel
Shin, I.-G.; Choi, J.-Y.; Park, S.-Y. et al

in Astrophysical Journal (2012), 746

Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of eight binary-lensing events detected ... [more ▼]

Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of eight binary-lensing events detected through the channel of high-magnification events during the seasons from 2007 to 2010. The perturbations, which are confined near the peak of the light curves, can be easily distinguished from the central perturbations caused by planets. However, the degeneracy between close and wide binary solutions cannot be resolved with a 3σ confidence level for three events, implying that the degeneracy would be an important obstacle in studying binary distributions. The dependence of the degeneracy on the lensing parameters is consistent with a theoretical prediction that the degeneracy becomes severe as the binary separation and the mass ratio deviate from the values of resonant caustics. The measured mass ratio of the event OGLE-2008-BLG-510/MOA-2008-BLG-369 is q ~ 0.1, making the companion of the lens a strong brown dwarf candidate. [less ▲]

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See detailA brown dwarf orbiting an M-dwarf: MOA 2009-BLG-411L
Bachelet, E.; Fouqué, P.; Han, C. et al

in Astronomy and Astrophysics (2012), 547

Context. Caustic crossing is the clearest signature of binary lenses in microlensing. In the present context, this signature is diluted by the large source star but a detailed analysis has allowed the ... [more ▼]

Context. Caustic crossing is the clearest signature of binary lenses in microlensing. In the present context, this signature is diluted by the large source star but a detailed analysis has allowed the companion signal to be extracted. <BR /> Aims: MOA 2009-BLG-411 was detected on August 5, 2009 by the MOA-Collaboration. Alerted as a high-magnification event, it was sensitive to planets. Suspected anomalies in the light curve were not confirmed by a real-time model, but further analysis revealed small deviations from a single lens extended source fit. <BR /> Methods: Thanks to observations by all the collaborations, this event was well monitored. We first decided to characterize the source star properties by using a more refined method than the classical one: we measure the interstellar absorption along the line of sight in five different passbands (VIJHK). Secondly, we model the lightcurve by using the standard technique: make (s,q,α) grids to look for local minima and refine the results by using a downhill method (Markov chain Monte Carlo). Finally, we use a Galactic model to estimate the physical properties of the lens components. <BR /> Results: We find that the source star is a giant G star with radius 9 R[SUB]&sun;[/SUB]. The grid search gives two local minima, which correspond to the theoretical degeneracy s ≡ s[SUP]-1[/SUP]. We find that the lens is composed of a brown dwarf secondary of mass M[SUB]S[/SUB] = 0.05 M[SUB]&sun;[/SUB] orbiting a primary M-star of mass M[SUB]P[/SUB] = 0.18 M[SUB]&sun;[/SUB]. We also reveal a new mass-ratio degeneracy for the central caustics of close binaries. <BR /> Conclusions: As far as we are aware, this is the first detection using the microlensing technique of a binary system in our Galaxy composed of an M-star and a brown dwarf. Appendix is available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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See detailDiscovery and Mass Measurements of a Cold, 10 Earth Mass Planet and Its Host Star
Muraki, Y.; Han, C.; Bennett, D. P. et al

in Astrophysical Journal (2011), 741

We present the discovery and mass measurement of the cold, low-mass planet MOA-2009-BLG-266Lb, performed with the gravitational microlensing method. This planet has a mass of m[SUB]p[/SUB] = 10.4 ± 1.7 M ... [more ▼]

We present the discovery and mass measurement of the cold, low-mass planet MOA-2009-BLG-266Lb, performed with the gravitational microlensing method. This planet has a mass of m[SUB]p[/SUB] = 10.4 ± 1.7 M[SUB]⊕[/SUB] and orbits a star of mass M [SUB]sstarf[/SUB] = 0.56 ± 0.09 M[SUB]sun[/SUB] at a semimajor axis of a = 3.2{+1.9\atop -0.5} AU and an orbital period of P = 7.6{+7.7\atop -1.5} yrs. The planet and host star mass measurements are enabled by the measurement of the microlensing parallax effect, which is seen primarily in the light curve distortion due to the orbital motion of the Earth. But the analysis also demonstrates the capability to measure the microlensing parallax with the Deep Impact (or EPOXI) spacecraft in a heliocentric orbit. The planet mass and orbital distance are similar to predictions for the critical core mass needed to accrete a substantial gaseous envelope, and thus may indicate that this planet is a "failed" gas giant. This and future microlensing detections will test planet formation theory predictions regarding the prevalence and masses of such planets. [less ▲]

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See detailMOA-2009-BLG-387Lb: a massive planet orbiting an M dwarf
Batista, V.; Gould, A.; Dieters, S. et al

in Astronomy and Astrophysics (2011), 529

<BR /> Aims: We report the discovery of a planet with a high planet-to-star mass ratio in the microlensing event MOA-2009-BLG-387, which exhibited pronounced deviations over a 12-day interval, one of the ... [more ▼]

<BR /> Aims: We report the discovery of a planet with a high planet-to-star mass ratio in the microlensing event MOA-2009-BLG-387, which exhibited pronounced deviations over a 12-day interval, one of the longest for any planetary event. The host is an M dwarf, with a mass in the range 0.07 M[SUB]&sun;[/SUB] < M[SUB]host[/SUB] < 0.49 M[SUB]&sun;[/SUB] at 90% confidence. The planet-star mass ratio q = 0.0132 ± 0.003 has been measured extremely well, so at the best-estimated host mass, the planet mass is m[SUB]p[/SUB] = 2.6 Jupiter masses for the median host mass, M = 0.19 M[SUB]&sun;[/SUB]. <BR /> Methods: The host mass is determined from two "higher order" microlensing parameters. One of these, the angular Einstein radius θ[SUB]E[/SUB] = 0.31 ± 0.03 mas has been accurately measured, but the other (the microlens parallax π[SUB]E[/SUB], which is due to the Earth's orbital motion) is highly degenerate with the orbital motion of the planet. We statistically resolve the degeneracy between Earth and planet orbital effects by imposing priors from a Galactic model that specifies the positions and velocities of lenses and sources and a Kepler model of orbits. <BR /> Results: The 90% confidence intervals for the distance, semi-major axis, and period of the planet are 3.5 kpc < D[SUB]L[/SUB] < 7.9 kpc, 1.1 AU < a < 2.7 AU, and 3.8 yr < P < 7.6 yr, respectively. Photometric data is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/529/A102">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/529/A102</A> [less ▲]

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See detailA sub-Saturn Mass Planet, MOA-2009-BLG-319Lb
Miyake, N.; Sumi, T.; Dong, Subo et al

in Astrophysical Journal (2011), 1010

We report the gravitational microlensing discovery of a sub-Saturn mass planet, MOA-2009-BLG-319Lb, orbiting a K or M-dwarf star in the inner Galactic disk or Galactic bulge. The high cadence observations ... [more ▼]

We report the gravitational microlensing discovery of a sub-Saturn mass planet, MOA-2009-BLG-319Lb, orbiting a K or M-dwarf star in the inner Galactic disk or Galactic bulge. The high cadence observations of the MOA-II survey discovered this microlensing event and enabled its identification as a high magnification event approximately 24 hours prior to peak magnification. As a result, the planetary signal at the peak of this light curve was observed by 20 different telescopes, which is the largest number of telescopes to contribute to a planetary discovery to date. The microlensing model for this event indicates a planet-star mass ratio of q = (3.95 +/- 0.02) x 10^{-4} and a separation of d = 0.97537 +/- 0.00007 in units of the Einstein radius. A Bayesian analysis based on the measured Einstein radius crossing time, t_E, and angular Einstein radius, \theta_E, along with a standard Galactic model indicates a host star mass of M_L = 0.38^{+0.34}_{-0.18} M_{Sun} and a planet mass of M_p = 50^{+44}_{-24} M_{Earth}, which is half the mass of Saturn. This analysis also yields a planet-star three-dimensional separation of a = 2.4^{+1.2}_{-0.6} AU and a distance to the planetary system of D_L = 6.1^{+1.1}_{-1.2} kpc. This separation is ~ 2 times the distance of the snow line, a separation similar to most of the other planets discovered by microlensing. [less ▲]

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See detailFrequency of Solar-like Systems and of Ice and Gas Giants Beyond the Snow Line from High-magnification Microlensing Events in 2005-2008
Gould, A.; Dong, Subo; Gaudi, B. S. et al

in Astrophysical Journal (2010), 720

We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval –4.5 < log q < –2, corresponding to the range of ice giants to gas giants. We ... [more ▼]

We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval –4.5 < log q < –2, corresponding to the range of ice giants to gas giants. We find \endgraf\vbox{\begin{center}$\displaystyle{d^2 N{_{\rm pl}}\over d\log q\, d\log s} = (0.36\pm 0.15)\;{\rm dex}^{-2}$\end{center}}\noindentat the mean mass ratio q = 5 × 10 –4 with no discernible deviation from a flat (Öpik's law) distribution in log-projected separation s. The determination is based on a sample of six planets detected from intensive follow-up observations of high-magnification ( A>200) microlensing events during 2005-2008. The sampled host stars have a typical mass M host ~ 0.5 M sun [less ▲]

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See detailOGLE 2008-BLG-290: an accurate measurement of the limb darkening of a galactic bulge K Giant spatially resolved by microlensing
Fouqué, P.; Heyrovský, D.; Dong, S. et al

in Astronomy and Astrophysics (2010), 518

Context. Not only is gravitational microlensing a successful tool for discovering distant exoplanets, but it also enables characterization of the lens and source stars involved in the lensing event. <BR ... [more ▼]

Context. Not only is gravitational microlensing a successful tool for discovering distant exoplanets, but it also enables characterization of the lens and source stars involved in the lensing event. <BR /> Aims: In high-magnification events, the lens caustic may cross over the source disk, which allows determination of the angular size of the source and measurement of its limb darkening. <BR /> Methods: When such extended-source effects appear close to maximum magnification, the resulting light curve differs from the characteristic Paczyński point-source curve. The exact shape of the light curve close to the peak depends on the limb darkening of the source. Dense photometric coverage permits measurement of the respective limb-darkening coefficients. <BR /> Results: In the case of the microlensing event OGLE 2008-BLG-290, the K giant source star reached a peak magnification at about 100. Thirteen different telescopes have covered this event in eight different photometric bands. Subsequent light-curve analysis yielded measurements of linear limb-darkening coefficients of the source in six photometric bands. The best-measured coefficients lead to an estimate of the source effective temperature of about 4700[SUP]+100[/SUP][SUB]-200[/SUB] K. However, the photometric estimate from colour-magnitude diagrams favours a cooler temperature of 4200 ± 100 K. <BR /> Conclusions: Because the limb-darkening measurements, at least in the CTIO/SMARTS2 V_s- and I_s-bands, are among the most accurate obtained, the above disagreement needs to be understood. A solution is proposed, which may apply to previous events where such a discrepancy also appeared. [less ▲]

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