Microlensing exoplanet discoveries

Spitzer Parallax of OGLE-2015-BLG-0966: A Cold Neptune in the Galactic Disk
http://arxiv.org/abs/1508.07027

Quote :

We report the detection of a Cold Neptune m_planet=21+/-2MEarth orbiting a 0.38MSol 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. (2015), 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 clearly not in the Galactic bulge.

I suggest to keep this topic open til official discovery paper is released:

MOA-2013-BLG-605Lb: The Neptune analog

Quote :

We present the discovery and mass measurement of the first Neptune analog exoplanet, MOA-2013-BLG-605Lb. This planet has a mass similar to that of Neptune and it orbits at a distance of 11 times the expected position of the snow-line, which is the same position as Neptune in our Solar System. This is the first sub-Jupiter-mass exoplanet found at such a large distance from its host star, although planets at similar separations have been found by direct imaging. There are two degenerate physical solutions due to a new type of degeneracy in the microlensing parallax parameters, known as the wide degeneracy. The slightly favored model has a Neptune-mass planet orbiting a low-mass M-dwarf. The alternative model implies a mini-Neptune orbiting a brown dwarf host. The 3-D planet-host separations are 11 times or 16 times greater than the expected positions of the snow-line for these models, respectively, which are close to Neptune's separation of 11 snow-line from the Sun. This discovery suggests that Neptune-like planets orbiting at 11 snow-line are quite common, so the process that formed Uranus and Neptune in our own Solar System may be quite common in other solar systems.

Conference PowerPoint file for further details:

http://asd.gsfc.nasa.gov/conferences/microlensing19/Sumi.pdf

P.S.

From the OGLE datapage of the event I get its position in Sagittarius.

The First Cold Neptune Analog Exoplanet: MOA-2013-BLG-605Lb
http://arxiv.org/abs/1512.00134

Three different models, each of them have a super-Earth or Neptune several times further from the star than the snow-line.

Stalker wrote:

https://solar-flux.forumotion.com/t1675-moa-2013-blg-605lb-the-neptune-analog

Yeah I thought it sounded familiar...
Merged.

MOA 2011-BLG-028Lb: a Neptune-mass Microlensing Planet in the Galactic Bulge
http://arxiv.org/abs/1512.03422

Quote :

We present the discovery of a Neptune-mass planet orbiting a 0.8 +- 0.3 M_Sun star in the Galactic bulge. The planet manifested itself during the microlensing event MOA 2011-BLG-028/OGLE-2011-BLG-0203 as a low-mass companion to the lens star. The analysis of the light curve provides the measurement of the mass ratio: (1.2 +- 0.2) x 10^-4, which indicates the mass of the planet to be 12-60 Earth masses. The lensing system is located at 7.3 +- 0.7 kpc away from the Earth near the direction to Baade's Window. The projected separation of the planet, at the time of the microlensing event, was 3.1-5.2 AU. Although the "microlens parallax" effect is not detected in the light curve of this event, preventing the actual mass measurement, the uncertainties of mass and distance estimation are narrowed by the measurement of the source star proper motion on the OGLE-III images spanning eight years, and by the low amount of blended light seen, proving that the host star cannot be too bright and massive. We also discuss the inclusion of undetected parallax and orbital motion effects into the models, and their influence onto the final physical parameters estimates.

A Super-Jupiter Microlens Planet Characterized by High-Cadence KMTNet Microlensing Survey Observations
http://arxiv.org/abs/1603.00020

Quote :

We report the characterization of a massive planet m_p=4.4 +- 1.6 M_jup orbiting an M dwarf host M=0.37 +- 0.14 M_sun at a distance of 0.6 +- 0.3 kpc toward the Galactic bulge, with planet host projected separation a_perp ~ 1.2 AU. The characterization was made possible by the wide-field (4 deg^2) high cadence (6/hr) monitoring of the Korea Microlensing Telescope Network (KMTNet), which had two of its three telescopes in commissioning operations at the time of the planetary anomaly. The source crossing time, t_* ~ 16 min, is among the shortest ever published. The high-cadence, wide-field observations that are the hallmark of KMTNet are the only way to routinely capture such short crossings. High-cadence resolution of short caustic crossings will preferentially lead to mass and distance measurements for the lens. This is because the short crossing time typically implies a nearby lens, which enables the measurement of additional effects (bright lens and/or microlens parallax). When combined with the measured crossing time, these effects can yield complete solutions.

A Super-Jupiter Microlens Planet Characterized by High-Cadence KMTNet Microlensing Survey Observations

Quote :

We report the characterization of a massive planet m_p=4.4 +- 1.6 M_jup orbiting an M dwarf host M=0.37 +- 0.14 M_sun at a distance of 0.6 +- 0.3 kpc toward the Galactic bulge, with planet host projected separation a_perp ~ 1.2 AU. The characterization was made possible by the wide-field (4 deg^2) high cadence (6/hr) monitoring of the Korea Microlensing Telescope Network (KMTNet), which had two of its three telescopes in commissioning operations at the time of the planetary anomaly. The source crossing time, t_* ~ 16 min, is among the shortest ever published. The high-cadence, wide-field observations that are the hallmark of KMTNet are the only way to routinely capture such short crossings. High-cadence resolution of short caustic crossings will preferentially lead to mass and distance measurements for the lens. This is because the short crossing time typically implies a nearby lens, which enables the measurement of additional effects (bright lens and/or microlens parallax). When combined with the measured crossing time, these effects can yield complete solutions.

Duplicate topic. Merged.

Sirius_Alpha wrote:

Duplicate topic. Merged.

OK

OGLE-2012-BLG-0724Lb: A Saturn-mass Planet around an M-dwarf
http://arxiv.org/abs/1604.05463

Quote :

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=(1.58±0.15)×10−3. By conducting a Bayesian analysis, we estimate that the host star is an M-dwarf star with a mass of ML=0.29+0.33−0.16 M⊙ located at DL=6.7+1.1−1.2 kpc away from the Earth and the companion's mass is mP=0.47+0.54−0.26 MJup. The projected planet-host separation is a⊥=1.6+0.4−0.3 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<mP/MJup<1) in contrast to a lack of Jupiters (∼1−2 MJup) around M-dwarfs, supporting the prediction by core accretion models that Jupiter-mass or more massive planets are unlikely to form around M-dwarfs.

Likely an M7-M8 star, an oasis in "Gas Giant Desert" around VLM stars.  

OGLE-2015-BLG-0051/KMT-2015-BLG-0048Lb: a Giant Planet Orbiting a Low-mass Bulge Star Discovered by High-cadence Microlensing Surveys

Quote :

We report the discovery of an extrasolar planet detected from the combined data of a microlensing event OGLE-2015-BLG-0051/KMT-2015-BLG-0048 acquired by two microlensing surveys. Despite that the short planetary signal occurred in the very early Bulge season during which the lensing event could be seen for just about an hour, the signal was continuously and densely covered. From the Bayesian analysis using models of the mass function, matter and velocity distributions combined with the information of the angular Einstein radius, it is found that the host of the planet is located in the Galactic bulge. The planet has a mass 0.72+0.65−0.07 MJ and it is orbiting a low-mass M-dwarf host with a projected separation d⊥=0.73±0.08 AU. The discovery of the planet demonstrates the capability of the current high-cadence microlensing lensing surveys in detecting and characterizing planets.

Another one but orbiting a slightly more massive M or late K dwarf:

OGLE-2012-BLG-0950Lb: The Possible First Planet Mass Measurement from Only Microlens Parallax and Lens Flux

Quote :

We report the discovery of a microlensing planet OGLE-2012-BLG-0950Lb with the planet/host mass ratio of q=2×10−4. A long term distortion detected in both MOA and OGLE light curve can be explained by the microlens parallax due to the Earth's orbital motion around the Sun. Although the finite source effect is not detected, we obtain the lens flux by the high resolution Keck AO observation. Combining the microlens parallax and the lens flux reveal the nature of the lens: a planet with mass of Mp=35+17−9MEarth is orbiting around a M-dwarf with mass of Mh=0.56+0.12−0.16MSun with a planet-host projected separation of rproj=2.7+0.6−0.7 AU located at DL=3.0+0.8−1.1 kpc from us. This is the first mass measurement from only microlens parallax and the lens flux without the finite source effect. The long term distortion can also be explained by the source orbital motion (xallarap) which is suspicious but not ruled out. These models can be distinguished by future high resolution imaging because of the much larger lens-source relative proper motion and brighter lens in the parallax model compared to the xallarap model. In the coming space observation-era with Spitzer, K2, Euclid, and WFIRST, we expect many such events for which we will not be able to measure any finite source effect. This work demonstrates an ability of mass measurements in such events.

And another.

OGLE-2016-BLG-0596Lb: High-Mass Planet From High-Magnification Pure-Survey Microlensing Event
http://arxiv.org/abs/1607.04919

Quote :

We report the discovery of a high mass-ratio planet q=0.012, i.e., 13 times higher than the Jupiter/Sun ratio. The host mass is not presently measured but can be determined or strongly constrained from adaptive optics imaging. The planet was discovered in a small archival study of high-magnification events in pure-survey microlensing data, which was unbiased by the presence of anomalies. The fact that it was previously unnoticed may indicate that more such planets lie in archival data and could be discovered by similar systematic study. In order to understand the transition from predominantly survey+followup to predominately survey-only planet detections, we conduct the first analysis of these detections in the observational (s,q) plane. Here s is projected separation in units of the Einstein radius. We find some evidence that survey+followup is relatively more sensitive to planets near the Einstein ring, but that there is no statistical difference in sensitivity by mass ratio.

Since this is becoming a rather generalised thread, I've changed the title (after all, we don't really need unique threads for planetary systems that none of us will likely live long enough to see studied in-depth).

Wise choice, Sirius!

Faint source star planetary microlensing: the discovery of the cold gas giant planet OGLE-2014-BLG-0676Lb
https://arxiv.org/abs/1612.03511

Quote :

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 M_jup planet orbiting a 0.62+0.20−0.22 M_sun 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.

https://www.nasa.gov/feature/goddard/2016/most-common-outer-planets-likely-neptune-mass

Microlensing Study Suggests Most Common Outer Planets Likely Neptune-mass

(NASA press release)

Quote :

https://www.nasa.gov/feature/goddard/2016/most-common-outer-planets-likely-neptune-mass

The preprint:

The Exoplanet Mass-Ratio Function from the MOA-II Survey: Discovery of a Break and Likely Peak at a Neptune Mass

Quote :

We report the results of the statistical analysis of planetary signals discovered in MOA-II microlensing survey alert system events from 2007 to 2012. We determine the survey sensitivity as a function of planet-star mass ratio, q, and projected planet-star separation, s, in Einstein radius units. We find that the mass ratio function is not a single power-law, but has a change in slope at q ∼ 10⁻⁴, corresponding to ∼20M_^⊕ for the median host star mass of ∼0.6M_⊙. We find significant planetary signals in 23 of the 1474 alert events that are well characterized by the MOA-II survey data alone. Data from other groups are used only to characterize planetary signals that have been identified in the MOA data alone. The distribution of mass ratios and separations of the planets found in our sample are well fit by a broken power-law model of the form dN_pl/(dlogq dlogs)=A(q/q_br)ⁿs^mdex⁻² for q > qbr and dN^pl/(dlogq dlogs)=A(q/qbr)^ps^mdex⁻² for q < q_br, where q_br is the mass ratio of the break. We also combine this analysis with the previous analyses of Gould et al. and Cassan et al., bringing the total sample to 30 planets. This combined analysis yields A=0.61^+0.21_−0.16, n=−0.93±0.13, m=0.49^+0.47_−0.49 and p=0.6^+0.5_−0.4 for qbr≡1.7×10−4. The unbroken power law model is disfavored with a p-value of 0.0022, which corresponds to a Bayes factor of 27 favoring the broken power-law model. These results imply that cold Neptunes are likely to be the most common type of planets beyond the snow line.

No other detection method is currently able to effectively reach this part of the mass-separation parameter space, so it will likely be some time until this result can be tested in the solar neighbourhood.

Couldn't find any mention of this planet on the forums, maybe we missed it the first time round?

Bhattacharya et al. "The Star Blended with the MOA-2008-BLG-310 Source Is Not the Exoplanet Host Star"
https://arxiv.org/abs/1703.06947

This ends up altering the system properties: mass of the star drops from ~0.67 to ~0.21 solar masses, planet from ~74 to ~23 Earth masses.

Lazarus wrote:

Couldn't find any mention of this planet on the forums, maybe we missed it the first time round?

https://solar-flux.forumotion.com/t349-moa-2008-blg-310lb-planet-in-the-galactic-bulge

Weird, Google didn't find it... I guess we should merge this with that thread. Or something.

OGLE-2013-BLG-1761Lb: A Massive Planet Around an M/K Dwarf
https://arxiv.org/abs/1703.07623

Quote :

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∼(7.5±1.5)×10−3 and q∼(9.3±2.9)×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 DL=6.9+1.0−1.2 kpc away from us and the host star is an M/K-dwarf with the mass of ML=0.33+0.32−0.18 M⊙ orbited by a super-Jupiter mass planet with the mass of mP=2.8+2.5−1.5 MJup at the projected separation of a⊥=1.8+0.5−0.5 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.

An Earth-mass Planet in a 1-AU Orbit around a Brown Dwarf
https://arxiv.org/abs/1703.08548

Quote :

We combine Spitzer and ground-based KMTNet microlensing observations to identify and precisely measure an Earth-mass (1.32+0.41−0.28M⊕) planet OGLE-2016-BLG-1195Lb at 1.11+0.13−0.10 AU orbiting a 0.072+0.014−0.010M⊙ ultracool dwarf, likely a brown dwarf. This is the lowest-mass microlensing planet to date. At 4.20+0.29−0.34 kpc, it is the third consecutive case among the Spitzer "Galactic distribution" planets toward the Galactic bulge that lies in the Galactic disk as opposed to the bulge itself, hinting at a skewed distribution of planets. Together with previous microlensing discoveries, the seven Earth-size planets orbiting the ultracool dwarf TRAPPIST-1, and the detection of disks around young brown dwarfs, OGLE-2016-BLG-1195Lb suggests that such planets might be common around ultracool dwarfs. It therefore sheds light on the formation of both brown dwarfs and planetary systems at the limit of low-mass protoplanetary disks.

The Lowest Mass Ratio Planetary Microlens: OGLE 2016-BLG-1195Lb
https://arxiv.org/abs/1703.08639

Quote :

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 ∼2.5hours. The measured ratio of the planet mass to its host star is q=4.2±0.7×10−5. We further estimate that the lens system is likely to comprise a cold ∼3 Earth mass planet in a ∼2 AU wide orbit around a 0.2 Solar mass star at an overall distance of 7.1 kpc.

Interesting system but Now I got confused,which one of the papers,the data it's more precise? Spitzer paper it's seems more precise.

MOA-2012-BLG-505Lb: A super-Earth mass planet in the Galactic bulge
https://arxiv.org/abs/1703.10769

Quote :

We report the discovery of a super-Earth mass planet in the microlensing event MOA-2012-BLG-505. This event has the second shortest event timescale of tE=10±1 days where the observed data show evidence of planetary companion. Our 15 minute high cadence survey observation schedule revealed the short subtle planetary signature. The system shows the well known close/wide degeneracy. The planet/host-star mass ratio is q=2.1×10−4 and the projected separation normalized by the Einstein radius is s = 1.1 or 0.9 for the wide and close solutions, respectively. We estimate the physical parameters of the system by using a Bayesian analysis and find that the lens consists of a super-Earth with a mass of 6.7+10.7−3.6M⊕ orbiting around a brown-dwarf or late M-dwarf host with a mass of 0.10+0.16−0.05M⊙ with a projected star-planet separation of 0.9+0.3−0.2AU. The system is at a distance of 7.2±1.1 kpc, i.e., it is likely to be in the Galactic bulge. The small angular Einstein radius (θE=0.12±0.02 mas) and short event timescale are typical for a low-mass lens in the Galactic bulge. Such low-mass planetary systems in the Bulge are rare because the detection efficiency of planets in short microlensing events is relatively low. This discovery may suggest that such low mass planetary systems are abundant in the Bulge and currently on-going high cadence survey programs will detect more such events and may reveal an abundance of such planetary systems.