Microlensing Observations in Astrophysics

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News Article | May 23, 2017
Site: phys.org

Gravitational microlensing is an invaluable method of detecting new extrasolar planets and brown dwarfs, regardless of the light they emit. This technique is therefore sensitive to the mass of the objects, rather than their luminosity, which allows astronomers to study objects that emit little or no light at all. Hence, due to their extremely low luminosities, brown-dwarf systems seem to be ideal targets for microlensing observations. Now, a team of astronomers led by Cheongho Han of the Chungbuk National University in Cheongju, South Korea, reports the detection of a new brown-dwarf binary system from the analysis of the microlensing event OGLE-2016-BLG-1469. The discovery is the result of a joint effort of over 50 scientists working in three microlensing research groups. The team consists of researchers from the Korea Microlensing Telescope Network (KMTNet), the Optical Gravitational Lensing Experiment (OGLE) and the Microlensing Observations in Astrophysics (MOA). "In this paper, we present the microlensing discovery of another binary system composed of brown dwarfs," the astronomers wrote in the paper. For their observations of OGLE-2016-BLG-1469, MOA researchers employed the 1.8m telescope at the Mt. John University Observatory in New Zealand, while OGLE scientists used the 1.3m telescope located at the Las Campanas Observatory in Chile. When it comes to KMTNet, the astronomers utilized three identical 1.6m telescopes located at the Cerro Tololo Inter-American Observatory in Chile, the South African Astronomical Observatory in South Africa, and the Siding Spring Observatory in Australia. All these ground-based observatories located worldwide allowed the team to find that the light curve of the microlensing event showcased a short-term central anomaly. This irregularity turned out to be produced by a binary companion with a mass roughly equal to the primary. More importantly, the researchers were able to determine the mass of both brown dwarfs and estimate their projected separation. They found that the mass of one of the newly discovered objects is about 0.05 solar masses, while the second one has approximately 0.01 the mass of the sun. The projected separation between the binary components was estimated to be 0.33 AU. Moreover, the study revealed that the system is located about 14,670 light years away from the Earth. "By measuring both the angular Einstein radius and the microlens parallax, we could uniquely determine the masses and identified the substellar nature of the lens components," the paper reads. According to the authors of the paper, their discovery shows the importance of the microlensing technique when it comes to finding new brown-dwarf binary systems. "The lens was the third microlensing brown-dwarf binary with measured mass, demonstrating the usefulness of the microlensing method in detecting field brown-dwarf binaries," the researchers concluded. Explore further: Astronomers discover new substellar companion using microlensing Abstract We report the discovery of a binary composed of two brown dwarfs, based on the analysis of the microlensing event OGLE-2016-BLG-1469. Thanks to detection of both finite-source and microlens-parallax effects, we are able to measure both the masses M1∼0.05 M⊙, M2∼0.01 M⊙, and distance DL∼4.5 kpc, as well as the projected separation a⊥∼0.33 au. This is the third brown-dwarf binary detected using the microlensing method, demonstrating the usefulness of microlensing in detecting field brown-dwarf binaries with separations less than 1 au.


News Article | April 18, 2017
Site: phys.org

Gravitational microlensing is an invaluable method of detecting new extrasolar planets circling their parent stars relatively closely. This technique is sensitive to low-mass planets orbiting beyond the so-called "snow line" around relatively faint host stars like M dwarfs or brown dwarfs. Such planets are of special interest for astronomers, as just beyond this line, the most active planet formation occurs. Hence, understanding the distribution of exoplanets in this region could offer important clues to how planets form. The microlensing event MOA-2016-BLG-227 was detected on May 5, 2016 by the Microlensing Observations in Astrophysics (MOA) group using the 1.8 m MOA-II telescope at the University of Canterbury Mt. John Observatory in New Zealand. Afterward, this event was the target of follow-up observations employing three telescopes located on Mauna Kea, Hawaii: the United Kingdom Infra-Red Telescope (UKIRT) 3.8m telescope, the Canada France Hawaii Telescope (CFHT) and the Keck II telescope. VLT Survey Telescope (VST) at ESO's Paranal Observatory in Chile and the Jay Baum Rich 0.71m Telescope (C28) at the Wise Observatory in Israel were also used for these observations. This subsequent observational campaign allowed the research team led by Naoki Koshimoto of the Osaka University in Japan to detect the new planet and to determine its basic parameters. "The event and planetary signal were discovered by the MOA collaboration, but much of the planetary signal is covered by the Wise, UKIRT, CFHT and VST telescopes, which were observing the event as part of the K2 C9 program (Campaign 9 of the Kepler telescope's prolonged mission)," the paper reads. The team found that MOA-2016-BLG-227Lb is a super-Jupiter planet with the mass of about 2.8 Jupiter masses. The parent star is most probably an M or K dwarf located in the galactic bulge. The mass of the star is estimated to be around 0.29 solar masses. MOA-2016-BLG-227Lb orbits its host at a distance of approximately 1.67 AU. Other main parameters like the radius of both objects and orbital period of the planet are yet to be determined. "Our analysis excludes the possibility that the host star is a G-dwarf, leading us to a robust conclusion that the planet MOA-2016-BLG-227Lb is a super-Jupiter mass planet orbiting an M or K-dwarf star likely located in the Galactic bulge," the researchers concluded. The authors call for further investigation of the MOA-2016-BLG-227 event, which could deliver essential more detailed information about the newly found planetary system. They noted that this event should be revisited with the Hubble Space Telescope (HST) and Keck adaptive optics (AO) system. Promising results could also come from future space and ground based telescopes like the James Webb Space Telescope (JWST), the Giant Magellan Telescope (GMT), the Thirty Meter Telescope and the Extremely Large Telescope (ELT). Explore further: Astronomers discover new substellar companion using microlensing More information: MOA-2016-BLG-227Lb: A Massive Planet Characterized by Combining Lightcurve Analysis and Keck AO Imaging, arXiv:1704.01724 [astro-ph.EP] arxiv.org/abs/1704.01724 Abstract We report the discovery of a microlensing planet —- MOA-2016-BLG-227Lb —- with a massive planet/host mass ratio of q≃9×10−3. This event was fortunately observed by several telescopes as the event location was very close to the area of the sky surveyed by Campaign 9 of the K2 Mission. Consequently, the planetary deviation is well covered and allows a full characterization of the lensing system. High angular resolution images by the Keck telescope show excess flux other than the source flux at the target position, and this excess flux could originate from the lens star. We combined the excess flux and the observed angular Einstein radius in a Bayesian analysis which considers various possible origins of the measured excess flux as priors, in addition to a standard Galactic model. Our analysis indicates that it is unlikely that a large fraction of the excess flux comes from the lens. We compare the results of the Bayesian analysis using different priors for the probability of hosting planets with respect to host mass and find the planet is likely a gas-giant around an M/K dwarf likely located in the Galactic bulge. This is the first application of a Bayesian analysis considering several different contamination scenarios for a newly discovered event. Our approach for considering different contamination scenarios is crucial for all microlensing events which have evidence for excess flux irrespective of the quality of observation conditions, such as seeing, for example.


News Article | May 8, 2017
Site: phys.org

The planets were discovered by researchers working as part of the Optical Gravitational Lensing Experiment (OGLE) group and the Microlensing Observations in Astrophysics (MOA) collaboration. OGLE uses the 1.3-m Warsaw Telescope located at Las Campanas Observatory in Chile, while MOA utilizes the 1.8-m MOA-II telescope at the Mount John University Observatory, located in New Zealand. The main goal of these two microlensing surveys is to study the planet formation around late-type stars. Gravitational microlensing is an invaluable method of detecting new extrasolar planets circling their parent stars relatively closely. This technique is sensitive to planets orbiting beyond the so-called "snow line" around relatively faint host stars like M dwarfs or brown dwarfs. It is a location in the proto-planetary disk where the water ice may condense and where gas giant planets are believed to be formed. Therefore, understanding the distribution of exoplanets in this region could offer important clues to how planets form. Recently, OGLE and MOA scientists led by Przemek Mróz of the Warsaw University Observatory in Poland, have found planetary anomalies in two faint microlensing events designated OGLE-2013-BLG-0132 and OGLE-2013-BLG-1721. "Both events showed clear deviations from the simple point-source point-lens model, caused by the presence of a second body with well-measured planet-to-host mass ratios of (5.15 ± 0.28) x 10-4 and (13.18 ± 0.72) x 10-4, respectively," the researchers wrote in the paper. The newly discovered planets received designation OGLE-2013-BLG-0132b and OGLE-2013-BLG-1721b. Both planets likely belong to a group of sub-Jupiter-mass planets orbiting M dwarfs beyond the snow line distance. According to the research, OGLE-2013-BLG-0132b has a mass of about 0.29 Jupiter masses and orbits its parent star at a distance of 3.6 AU. The planet's host is located about 12,700 light years away and has a mass of approximately 0.54 solar masses. With a mass of about 0.64 Jupiter masses, OGLE-2013-BLG-1721b is circling its host (0.46 solar masses) at a distance of 2.6 AU. This planetary system is located some 20,500 light years away from the Earth. The researchers estimated the masses of the planets using the Bayesian analysis as both events were short and faint, which prevented them from measuring a reliable parallax signal. "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 masses of both planets," the paper reads. The team noted that in order to uncover more properties of the two newly discovered planetary systems, follow-up high-resolution imaging observations should be conducted in the future. In particular, the Near InfRared Camera (NIRCam) on the James Webb Space Telescope (JWST) that will be launched into space in late 2018, could reveal important insights about these new Saturn-mass exoworlds. More information: OGLE-2013-BLG-0132Lb and OGLE-2013-BLG-1721Lb: Two Saturn-mass Planets Discovered around M-dwarfs, arXiv:1705.01058 [astro-ph.EP] arxiv.org/abs/1705.01058 Abstract 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 planet-host mass ratios are (5.15±0.28)×10−4 and (13.18±0.72)×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 masses of both planets: 0.29+0.16−0.13 MJup (OGLE-2013-BLG-0132Lb) and 0.64+0.35−0.31 M (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.


Bachelet E.,French National Center for Scientific Research | Fouque P.,French National Center for Scientific Research | Han C.,Microlensing Follow Up Network | Han C.,Chungbuk National University | And 160 more authors.
Astronomy and Astrophysics | Year: 2012

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. 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. 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. Results. We find that the source star is a giant G star with radius 9 R ·. The grid search gives two local minima, which correspond to the theoretical degeneracy s s-1. We find that the lens is composed of a brown dwarf secondary of mass MS = 0.05 M· orbiting a primary M-star of mass MP = 0.18 M·. We also reveal a new mass-ratio degeneracy for the central caustics of close binaries. 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. © 2012 ESO.


News Article | December 15, 2016
Site: www.eurekalert.org

A new statistical study of planets found by a technique called gravitational microlensing suggests that Neptune-mass worlds are likely the most common type of planet to form in the icy outer realms of planetary systems. The study provides the first indication of the types of planets waiting to be found far from a host star, where scientists suspect planets form most efficiently. "We've found the apparent sweet spot in the sizes of cold planets. Contrary to some theoretical predictions, we infer from current detections that the most numerous have masses similar to Neptune, and there doesn't seem to be the expected increase in number at lower masses," said lead scientist Daisuke Suzuki, a post-doctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland Baltimore County. "We conclude that Neptune-mass planets in these outer orbits are about 10 times more common than Jupiter-mass planets in Jupiter-like orbits." Gravitational microlensing takes advantage of the light-bending effects of massive objects predicted by Einstein's general theory of relativity. It occurs when a foreground star, the lens, randomly aligns with a distant background star, the source, as seen from Earth. As the lensing star drifts along in its orbit around the galaxy, the alignment shifts over days to weeks, changing the apparent brightness of the source. The precise pattern of these changes provides astronomers with clues about the nature of the lensing star, including any planets it may host. "We mainly determine the mass ratio of the planet to the host star and their separation," said team member David Bennett, an astrophysicist at Goddard. "For about 40 percent of microlensing planets, we can determine the mass of the host star and therefore the mass of the planet." More than 50 exoplanets have been discovered using microlensing compared to thousands detected by other techniques, such as detecting the motion or dimming of a host star caused by the presence of planets. Because the necessary alignments between stars are rare and occur randomly, astronomers must monitor millions of stars for the tell-tale brightness changes that signal a microlensing event. However, microlensing holds great potential. It can detect planets hundreds of times more distant than most other methods, allowing astronomers to investigate a broad swath of our Milky Way galaxy. The technique can locate exoplanets at smaller masses and greater distances from their host stars, and it's sensitive enough to find planets floating through the galaxy on their own, unbound to stars. NASA's Kepler and K2 missions have been extraordinarily successful in finding planets that dim their host stars, with more than 2,500 confirmed discoveries to date. This technique is sensitive to close-in planets but not more distant ones. Microlensing surveys are complementary, best probing the outer parts of planetary systems with less sensitivity to planets closer to their stars. "Combining microlensing with other techniques provides us with a clearer overall picture of the planetary content of our galaxy," said team member Takahiro Sumi at Osaka University in Japan. From 2007 to 2012, the Microlensing Observations in Astrophysics (MOA) group, a collaboration between researchers in Japan and New Zealand, issued 3,300 alerts informing the astronomical community about ongoing microlensing events. Suzuki's team identified 1,474 well-observed microlensing events, with 22 displaying clear planetary signals. This includes four planets that were never previously reported. To study these events in greater detail, the team included data from the other major microlensing project operating over the same period, the Optical Gravitational Lensing Experiment (OGLE), as well as additional observations from other projects designed to follow up on MOA and OGLE alerts. From this information, the researchers determined the frequency of planets compared to the mass ratio of the planet and star as well as the distances between them. For a typical planet-hosting star with about 60 percent the sun's mass, the typical microlensing planet is a world between 10 and 40 times Earth's mass. For comparison, Neptune in our own solar system has the equivalent mass of 17 Earths. The results imply that cold Neptune-mass worlds are likely to be the most common types of planets beyond the so-called snow line, the point where water remained frozen during planetary formation. In the solar system, the snow line is thought to have been located at about 2.7 times Earth's mean distance from the sun, placing it in the middle of the main asteroid belt today. A paper detailing the findings was published in The Astrophysical Journal on Dec. 13. "Beyond the snow line, materials that were gaseous closer to the star condense into solid bodies, increasing the amount of material available to start the planet-building process," said Suzuki. "This is where we think planetary formation was most efficient, and it's also the region where microlensing is most sensitive." NASA's Wide Field Infrared Survey Telescope (WFIRST), slated to launch in the mid-2020s, will conduct an extensive microlensing survey. Astronomers expect it will deliver mass and distance determinations of thousands of planets, completing the work begun by Kepler and providing the first galactic census of planetary properties. NASA's Ames Research Center manages the Kepler and K2 missions for NASA's Science Mission Directorate. The Jet Propulsion Laboratory (JPL) in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. WFIRST is managed at Goddard, with participation by JPL, the Space Telescope Science Institute in Baltimore, the Infrared Processing and Analysis Center, also in Pasadena, and a science team comprising members from U.S. research institutions across the country. For more information on how NASA's Kepler is working with ground-based efforts, including the MOA and OGLE groups, to search for planets using microlensing, please visit:


News Article | December 15, 2016
Site: phys.org

"We've found the apparent sweet spot in the sizes of cold planets. Contrary to some theoretical predictions, we infer from current detections that the most numerous have masses similar to Neptune, and there doesn't seem to be the expected increase in number at lower masses," said lead scientist Daisuke Suzuki, a post-doctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland Baltimore County. "We conclude that Neptune-mass planets in these outer orbits are about 10 times more common than Jupiter-mass planets in Jupiter-like orbits." Gravitational microlensing takes advantage of the light-bending effects of massive objects predicted by Einstein's general theory of relativity. It occurs when a foreground star, the lens, randomly aligns with a distant background star, the source, as seen from Earth. As the lensing star drifts along in its orbit around the galaxy, the alignment shifts over days to weeks, changing the apparent brightness of the source. The precise pattern of these changes provides astronomers with clues about the nature of the lensing star, including any planets it may host. "We mainly determine the mass ratio of the planet to the host star and their separation," said team member David Bennett, an astrophysicist at Goddard. "For about 40 percent of microlensing planets, we can determine the mass of the host star and therefore the mass of the planet." More than 50 exoplanets have been discovered using microlensing compared to thousands detected by other techniques, such as detecting the motion or dimming of a host star caused by the presence of planets. Because the necessary alignments between stars are rare and occur randomly, astronomers must monitor millions of stars for the tell-tale brightness changes that signal a microlensing event. However, microlensing holds great potential. It can detect planets hundreds of times more distant than most other methods, allowing astronomers to investigate a broad swath of our Milky Way galaxy. The technique can locate exoplanets at smaller masses and greater distances from their host stars, and it's sensitive enough to find planets floating through the galaxy on their own, unbound to stars. NASA's Kepler and K2 missions have been extraordinarily successful in finding planets that dim their host stars, with more than 2,500 confirmed discoveries to date. This technique is sensitive to close-in planets but not more distant ones. Microlensing surveys are complementary, best probing the outer parts of planetary systems with less sensitivity to planets closer to their stars. "Combining microlensing with other techniques provides us with a clearer overall picture of the planetary content of our galaxy," said team member Takahiro Sumi at Osaka University in Japan. From 2007 to 2012, the Microlensing Observations in Astrophysics (MOA) group, a collaboration between researchers in Japan and New Zealand, issued 3,300 alerts informing the astronomical community about ongoing microlensing events. Suzuki's team identified 1,474 well-observed microlensing events, with 22 displaying clear planetary signals. This includes four planets that were never previously reported. To study these events in greater detail, the team included data from the other major microlensing project operating over the same period, the Optical Gravitational Lensing Experiment (OGLE), as well as additional observations from other projects designed to follow up on MOA and OGLE alerts. From this information, the researchers determined the frequency of planets compared to the mass ratio of the planet and star as well as the distances between them. For a typical planet-hosting star with about 60 percent the sun's mass, the typical microlensing planet is a world between 10 and 40 times Earth's mass. For comparison, Neptune in our own solar system has the equivalent mass of 17 Earths. The results imply that cold Neptune-mass worlds are likely to be the most common types of planets beyond the so-called snow line, the point where water remained frozen during planetary formation. In the solar system, the snow line is thought to have been located at about 2.7 times Earth's mean distance from the sun, placing it in the middle of the main asteroid belt today. A paper detailing the findings was published in The Astrophysical Journal on Dec. 13. "Beyond the snow line, materials that were gaseous closer to the star condense into solid bodies, increasing the amount of material available to start the planet-building process," said Suzuki. "This is where we think planetary formation was most efficient, and it's also the region where microlensing is most sensitive." NASA's Wide Field Infrared Survey Telescope (WFIRST), slated to launch in the mid-2020s, will conduct an extensive microlensing survey. Astronomers expect it will deliver mass and distance determinations of thousands of planets, completing the work begun by Kepler and providing the first galactic census of planetary properties. NASA's Ames Research Center manages the Kepler and K2 missions for NASA's Science Mission Directorate. The Jet Propulsion Laboratory (JPL) in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. WFIRST is managed at Goddard, with participation by JPL, the Space Telescope Science Institute in Baltimore, the Infrared Processing and Analysis Center, also in Pasadena, and a science team comprising members from U.S. research institutions across the country. More information: "The Exoplanet Mass-ratio Function from the MOA-II Survey: Discovery of a Break and Likely Peak at a Neptune Mass," D. Suzuki et al., 2016 Dec. 20, Astrophysical Journal iopscience.iop.org/article/10.3847/1538-4357/833/2/145 , Arxiv: arxiv.org/abs/1612.03939


Fouque P.,French National Center for Scientific Research | Heyrovsky D.,Charles University | Dong S.,Microlensing Follow Up Network | Dong S.,Ohio State University | And 144 more authors.
Astronomy and Astrophysics | Year: 2010

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. 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. 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. 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$^{+100}-{-200}$ K. However, the photometric estimate from colour-magnitude diagrams favours a cooler temperature of 4200 ± 100 K. Conclusions. Because the limb-darkening measurements, at least in the CTIO/SMARTS2 Vs- and Is-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. © 2010 ESO.


News Article | December 14, 2016
Site: phys.org

Unlike other methods of detecting exoplanets, microlensing is most sensitive when it comes to searching for exoworlds that orbit around one to 10 AU away from their host stars. These planets are of special interest for astronomers studying planetary formation theories due to proximity to their parent stars, within the so-called "snow line." Just beyond this line, the most active planet formation occurs; therefore, understanding the distribution of exoplanets in this region could offer important clues to how planets form. So far, 47 planets have been discovered by microlensing. Currently, several ground-based observation programs routinely monitor dense stellar fields to search for microlensing events. When a new event is discovered, an alert to the broader scientific community is issued in order to allow follow-up observations. Astronomers are particularly interested in events showing evidence for perturbations that could be due to the presence of a planet, or which are predicted to have a high sensitivity to such perturbations. OGLE-2014-BLG-0676, discovered in April 2014 by a Polish astronomical project called the Optical Gravitational Lensing Experiment (OGLE), is one of those interesting microlensing events. Recently, a collaboration of researchers consisting of the OGLE group, the Microlensing Observations in Astrophysics (MOA), the Wise Observatory Group and the Microlensing Network for the Detection of Small Terrestrial Exoplanets (MiNDSTEp), has detected an anomalous signal in this event consistent with a planetary lens system. "The source star passed through the central caustic, with the second caustic crossing being well recorded by the MOA microlensing survey collaboration. Observations at epochs between the unrecorded first caustic crossing and the second caustic crossing were made by the OGLE, Wise and MOA collaborations. (…) All analyses of the light curve data favor a lens system comprising a planetary mass orbiting a host star," the paper reads. According to the research, the newly discovered planet has a mass of about 3.1 Jupiter masses and orbits its parent star at a deprojected orbital separation of about 4.4 AU. The host star is approximately 38 percent less massive than our sun and was classified as a K-dwarf. The distance to the lens system is about 7,200 light years. Moreover, the team revealed some information about the source star. They revealed that is rather faint and very red, noting that there is a possibility that the source may be blended with a nearby red star, causing an incorrect identification of the source star type. In conclusion, the scientists emphasize the importance of their discovery, noting that OGLE-2014-BLG-0676Lb could serve as a test bed for planet formation scenarios. "Planet OGLE-2014-BLG-0676Lb can be added to the growing list of planets discovered by microlensing against which planetary formation theories can be tested," the researchers wrote in the paper. More information: N. J. Rattenbury et al. Faint source star planetary microlensing: the discovery of the cold gas giant planet OGLE-2014-BLG-0676Lb, Monthly Notices of the Royal Astronomical Society (2016). DOI: 10.1093/mnras/stw3185 , On Arxiv: https://arxiv.org/abs/1612.03511 Abstract 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.

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