46 research outputs found
Microlensing search for extrasolar planets: observational strategy, discoveries and implications
Microlensing has proven to be a valuable tool to search for extrasolar
planets of Jovian- to Super-Earth-mass planets at orbits of a few AU. Since
planetary signals are of very short duration, an intense and continuous
monitoring is required. This is achieved by ground-based networks of telescopes
(PLANET/RoboNET, microFUN) following up targets, which are identified as
microlensing events by single dedicated telescopes (OGLE, MOA). Microlensing
has led to four already published detections of extrasolar planets, one of them
being OGLE-2005-BLG-390Lb, a planet of only ~5.5 M_earth orbiting its M-dwarf
host star at ~2.6 AU. Very recent observations (May--September 2007) provided
more planetary candidates, still under study, that will double the number of
detections. For non-planetary microlensing events observed from 1995 to 2006 we
compute detection efficiency diagrams, which can then be used to derive an
estimate of the Galactic abundance of cool planets in the mass regime from
Jupiters to Sub-Neptunes.Comment: 4 pages, 2 figures. To appear in the proceedings of "IAU conference
249: Exoplanets: Detection, Formation and Dynamics", held in Suzhou, China,
22-26 Oct. 200
ROME/REA : a gravitational microlensing search for exoplanets beyond the snow line on a global network of robotic telescopes
Funding: KH acknowledges support from STFC grant ST/R000824/1.Planet population synthesis models predict an abundance of planets with semimajor axes between 1 and 10 au, yet they lie at the edge of the detection limits of most planet finding techniques. Discovering these planets and studying their distribution is critical to understanding the physical processes that drive planet formation. ROME/REA is a gravitational microlensing project whose main science driver is to discover exoplanets in the cold outer regions of planetary systems. To achieve this, it uses a novel approach combining a multiband survey with reactive follow-up observations, exploiting the unique capabilities of the Las Cumbres Observatory global network of robotic telescopes combined with a Target and Observation Manager system. We present the main science objectives and a technical overview of the project, including initial results.PostprintPeer reviewe
Microlensing mass measurement from images of rotating gravitational arcs
Gravitational microlensing[SUP]1[/SUP] is a powerful technique for measuring the mass of isolated and faint or non-luminous objects in the Milky Way[SUP]2,3[/SUP]. In most cases, however, additional observations to the photometric light curve are required to measure accurately the mass of the microlens. Long-baseline optical/infrared interferometry provides a new and efficient way to deliver such independent constraints[SUP]4-7[/SUP], as demonstrated recently by first interferometric observations in microlensing event TCP J05074264+2447555 (`Kojima-1')[SUP]8[/SUP]. Here we report real-time observations of gravitationally lensed arcs in rotation around a microlens, Gaia19bld[SUP]9[/SUP], made with the PIONIER instrument[SUP]10[/SUP] at the Very Large Telescope Interferometer. Our data allowed us to determine the angular separation and length of the arcs, as well as their rotation rate. Combining these measurements with ground-based photometric data enabled the determination of the microlens mass, M = 1.147 ± 0.029 M[SUB]â[/SUB], to a very high accuracy. We anticipate interferometric microlensing to play an important future role in the mass and distance determination of isolated stellar-mass black holes[SUP]11-13[/SUP] in the Galaxy, which cannot be addressed by any other technique
Spectroscopic Mass and Host-star Metallicity Measurements for Newly Discovered Microlensing Planet OGLE-2018-BLG-0740Lb
We report the discovery of the microlensing planet OGLE-2018-BLG-0740Lb. The
planet is detected with a very strong signal of , 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 and the mass
of the planet is (close solution) or (wide solution) and the lens is located at a distance of ~kpc.
The bright nature of the lens, with (), 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 .Comment: 12 pages, 11 figures, 4 table
OGLE-2018-BLG-0022: First Prediction of an Astrometric Microlensing Signal from a Photometric Microlensing Event
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 and 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
Masses and Distances of Planetary Microlens Systems with High Angular Resolution Imaging
Microlensing is the only method that can detect and measure mass of wide
orbit, low mass, solar system analog exoplanets. Mass measurements of such
planets would yield massive science on planet formation, exoplanet
demographics, free floating planets, planet frequencies towards the galaxy.
High res follow-up observations of past microlens targets provide a mass
measurement of microlens planets and hosts at an uncertainty of <20%. This will
be primary method for mass measurement with WFIRST. We advocate for the fact
that high resolution observations with AO, HST and JWST(in future) remain
necessary in coming decade to develop the methods, to determine the field and
filter selection, understand the systematics and to develop a robust pipeline
to release high quality data products from WFIRST microlensing survey such that
the astronomy community can promptly engage in the science. We also support
future high res obs with US ELTs with advanced Laser AO systems in context of
enhancing the science return of WFIRST microlensing survey.
We endorse the 2018 Exoplanet Science Strategy report published by the
National Academy. This white paper extends and complements the material
presented therein. In particular, this white paper supports the recommendation
of the National Academy Exoplanet Science Strategy report that: NASA should
launch WFIRST to conduct its microlensing survey of distant planets and to
demonstrate the technique of coronagraphic spectroscopy on exoplanet targets.
This white paper also supports to the finding from that report which states "A
number of activities, including precursor and concurrent observations using
ground- and space-based facilities, would optimize the scientific yield of the
WFIRST microlensing survey."Comment: 8 pages, 2 figures, Astro2020 decadal submissio
OGLE-2018-BLG-1011Lb,c: Microlensing planetary system with two giant planets orbiting a low-mass star
We report a multiplanetary system found from the analysis of microlensing event OGLE-2018-BLG-1011, for which the light curve exhibits a double-bump anomaly around the peak. We find that the anomaly cannot be fully explained by the binary-lens or binary-source interpretations and its description requires the introduction of an additional lens component. The 3L1S (three lens components and a single source) modeling yields three sets of solutions, in which one set of solutions indicates that the lens is a planetary system in a binary, while the other two sets imply that the lens is a multiplanetary system. By investigating the fits of the individual models to the detailed light curve structure, we find that the multiple-planet solution with planet-to-host mass ratios âŒ9.5 Ă10-3 and âŒ15 Ă10-3 are favored over the other solutions. From the Bayesian analysis, we find that the lens is composed of two planets with masses 1.8+3.4-1.1MJ and 2.8+5.11.7 MJ around a host with a mass 0.18 +0.33-0.10M0 and located at a distance 7.1+1.1-1.5 kpc. The estimated distance indicates that the lens is the farthest system among the known multiplanetary systems. The projected planet-host separations are a â„,2 = 1.8+2.1-1.5 au (0.8+0.9-0.6 au) and a â„,3 = 0.8+0.9-0.6 where the values of a â„,2 inside and outside the parenthesis are the separations corresponding to the two degenerate solutions, indicating that both planets are located beyond the snow line of the host, as with the other four multiplanetary systems previously found by microlensing
Masses and Distances of Planetary Microlens Systems with High Angular Resolution Imaging
Microlensing is the only method that can detect and measure mass of wide orbit, low mass, solar system analog exoplanets. Mass measurements of such planets would yield massive science on planet formation, exoplanet demographics, free floating planets, planet frequencies towards the galaxy. High res follow-up observations of past microlens targets provide a mass measurement of microlens planets and hosts at an uncertainty of <20%. This will be primary method for mass measurement with WFIRST. We advocate for the fact that high resolution observations with AO, HST and JWST(in future) remain necessary in coming decade to develop the methods, to determine the field and filter selection, understand the systematics and to develop a robust pipeline to release high quality data products from WFIRST microlensing survey such that the astronomy community can promptly engage in the science. We also support future high res obs with US ELTs with advanced Laser AO systems in context of enhancing the science return of WFIRST microlensing survey.
We endorse the 2018 Exoplanet Science Strategy report published by the National Academy. This white paper extends and complements the material presented therein. In particular, this white paper supports the recommendation of the National Academy Exoplanet Science Strategy report that: NASA should launch WFIRST to conduct its microlensing survey of distant planets and to demonstrate the technique of coronagraphic spectroscopy on exoplanet targets. This white paper also supports to the finding from that report which states "A number of activities, including precursor and concurrent observations using ground- and space-based facilities, would optimize the scientific yield of the WFIRST microlensing survey.