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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

New giant planet beyond the snow line for an extended MOA exoplanet microlens sample

Characterizing a planet detected by microlensing is hard if the planetary signal is weak or the lens-source relative trajectory is far from caustics. However, statistical analyses of planet demography must include those planets to accurately determine occurrence rates. As part of a systematic modelling effort in the context of a >10-yr retrospective analysis of MOA’s survey observations to build an extended MOA statistical sample, we analyse the light curve of the planetary microlensing event MOA-2014-BLG-472. This event provides weak constraints on the physical parameters of the lens, as a result of a planetary anomaly occurring at low magnification in the light curve. We use a Bayesian analysis to estimate the properties of the planet, based on a refined Galactic model and the assumption that all Milky Way’s stars have an equal planet-hosting probability. We find that a lens consisting of a 1.9(+2.2,−1.2)M(J) giant planet orbiting a 0.31(+0.36,−0.19)Mꙩ host at a projected separation of 0.75±0.24au is consistent with the observations and is most likely, based on the Galactic priors. The lens most probably lies in the Galactic bulge, at 7.2(+0.6,−1.7)kpc from Earth. The accurate measurement of the measured planet-to-host star mass ratio will be included in the next statistical analysis of cold planet demography detected by microlensing.

Clément Ranc↗
NASA NTRS2016

Ogle-2012-blg-0724lb: A Saturn Mass Planet Around an M-dwarf

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) x 10(exp -3). By conducting a Bayesian analysis, we estimate that the host star is an M dwarf with a mass of M(sub L) = 0.29(+0.33/-0.16) solar mass located at D(sub L) = 6.7(+1.1/-1.2) kpc away from the Earth and the companion's mass is m(sub P) = 0.47(+0.54/-0.26) M(Jup). The projected planet- host separation is a falsum = 1.6(+0.4/-0.3) AU. Because the lens-source relative proper motion is relatively high, future highresolution 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 another example of a possible pileup of sub-Jupiters (0.2 less than m(sub P)/M(sub Jup) less than 1) in contrast to a lack of Jupiters (approximately 1-2 M(sub Jup)) around M dwarfs, supporting the prediction by core accretion models that Jupiter-mass or more massive planets are unlikely to form around M dwarfs.

microlensing↗
NASA NTRS2021

KMT-2019-BLG-0371 and the Limits of Bayesian Analysis

We show that the perturbation at the peak of the light curve of microlensing event KMT-2019-BLG-0371 is explained by a model with a mass ratio between the host star and planet of q ∼ 0.08. Due to the short event duration (t(sub E) ∼ 6.5 days), the secondary object in this system could potentially be a massive giant planet. A Bayesian analysis shows that the system most likely consists of a host star with a mass M(sub h) = 0.09(+0.14/-0.05) M⨀ and a massive giant planet with a mass = M(sub h) = 7.70(+11.34/-3.90) M(sub Jup). However, the interpretation of the secondary as a planet (i.e., as having M(sub p) < 13M(sub Jup)) rests entirely on the Bayesian analysis. Motivated by this event, we conduct an investigation to determine which constraints meaningfully affect Bayesian analyses for microlensing events. We find that the masses inferred from such a Bayesian analysis are determined almost entirely by the measured value of θ(sub E) and are relatively insensitive to other factors such as the direction of the event (l,b), the lens–source relative proper motion μ(sub rel), or the specific Galactic model prior.

Binary lens microlensing↗
DOE OSTI2012

On photo-expansion and microlens formation in (GeS{sub 2}){sub 0.74}(Sb{sub 2}S{sub 3}){sub 0.26} chalcogenide glass

Graphical abstract: Display Omitted Highlights: ► Photo-expansion induced by sub-band-gap photons in GeSbS glass. ► One-step microlens formation. ► The topography of the microlenses detected by AFM and DHM. ► The good mechanical characteristics of the microlenses were obtained. ► Local light-induced overheating of the glass. -- Abstract: Photo-expansion of the bulk of (GeS{sub 2}){sub 0.74}(Sb{sub 2}S{sub 3}){sub 0.26} glass induced by sub-gap photons is studied employing specifically atomic force microscopy (AFM) namely an atomic force acoustic microscopy (AFAM) and a force spectroscopy and digital holographic microscopy. The results are discussed with respect to the possible role of light induced overheating in the process of photo-expansion.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Multifunctional Liquid Marble Compound Lenses

Mosquito compound eyes are elaborate multifunctional hierarchical structures. The presence of ordered curved features spanning length scales of nanometers to millimeters provides the mosquito eye with a wide field of view, an infinite depth of field, as well as antifogging properties. Developing bio-inspired compound lenses is challenging because of the need to mimic all characteristic curvatures along with their functionalities. Herein, we show how the curvature inherent to nanoparticles, emulsion droplets, and liquid marbles can be employed to mimic the hierarchical structure and functionality of mosquito compound eyes. At the nanometers to micron length scale we employ nanoparticle-stabilized emulsion droplets of photocurable oil to form microlenses with nanoscale surface features. After polymerization, the microlenses form a monolayer on an oil droplet to create an optically clear, millimeter scale, liquid marble that functions as a compound lens. Here, we characterize the optical and surface properties of the compound lenses and find that they reproduce the functionality of the mosquito eye. Furthermore, we exploit the mobility and reconfigurability of liquid marbles to create arrays (centimeter scale) of compound lenses and other types of functional lenses such as the Janus lens that magnifies the image acquired by the compound lens. Simple and scalable methods to create compound lenses could aid in the development of miniaturized advanced vision systems.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Review of High-Throughput Surface Treatments for Microlens Arrays

Microlenses are increasingly being integrated into modern manufactured devices. From printed security devices and screens to solar panels and microscopes, these optical materials offer high control over light focusing. Thus, understanding how to treat the surfaces of these fragile, transparent devices on an integrated manufacturing line is essential. Here, in this study, we review the surface treatments for the following application categories: cleaning, increasing surface energy, decreasing surface energy, and tunable surface modifications. This overview describes methods available for the large-scale manufacturing of microlens arrays and the potential impact of those treatments on common optical surfaces. Objectives and qualitative compatibility parameters are compared, and outlooks are provided for further study to aid in streamlining the method selection and process optimization for microlenses and similar optical components.

lens manufacturing↗
DOE OSTI2018

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses: XVI. Time delays for the quadruply imaged quasar DES J0408–5354 with high-cadence photometric monitoring* [COSMOGRAIL XVI: Time delays for the quadruply imaged quasar DES J0408–5354 with high-cadence photometric monitoring]

Here, we present time-delay measurements for the new quadruple imaged quasar DES J0408–5354, the first quadruple imaged quasar found in the Dark Energy Survey (DES). Our result is made possible by implementing a new observational strategy using almost daily observations with the MPIA 2.2 m telescope at La Silla observatory and deep exposures reaching a signal-to-noise ratio of about 1000 per quasar image. This data qualityallows us to catch small photometric variations (a few mmag rms) of the quasar, acting on temporal scales much shorter than microlensing, and hence making the time delay measurement very robust against microlensing. In only seven months we very accurately measured one of the time delays in DES J0408–5354: Δt(AB) = –112.1 ± 2.1 days (1.8%) using only the MPIA 2.2 m data. In combination with data taken with the 1.2 m Euler Swiss telescope, we also measured two delays involving the D component of the system Δt(AD) = –155.5 ± 12.8 days (8.2%) and Δt(BD) = –42.4 ± 17.6 days (41%), where all the error bars include systematics. Turning these time delays into cosmological constraints will require deep Hubble Space Telescope (HST) imaging or ground-based adaptive optics (AO), and information on the velocity field of the lensing galaxy.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

COSMOGRAIL: XVII. Time delays for the quadruply imaged quasar PG 1115+080

Here, we present time-delay estimates for the quadruply imaged quasar PG 1115+080. Our results are based on almost daily observations for seven months at the ESO MPIA 2.2m telescope at La Silla Observatory, reaching a signal-to-noise ratio of about 1000 per quasar image. In addition, we re-analyze existing light curves from the literature that we complete with an additional three seasons of monitoring with the Mercator telescope at La Palma Observatory. When exploring the possible source of bias we consider the so-called microlensing time delay, a potential source of systematic error so far never directly accounted for in previous time-delay publications. In fifteen years of data on PG 1115+080, we find no strong evidence of microlensing time delay. Therefore not accounting for this effect, our time-delay estimates on the individual data sets are in good agreement with each other and with the literature. Combining the data sets, we obtain the most precise time-delay estimates to date on PG 1115+080, with Δt(AB) = 8.3 +1.5 –1.6 days (18.7% precision), Δt(AC) = 9.9 +1.1 –1.1 days (11.1%) and Δt(BC) = 18.8 +1.6 –1.6 days (8.5%). Turning these time delays into cosmological constraints is done in a companion paper that makes use of ground-based Adaptive Optics (AO) with the Keck telescope.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

COSMOGRAIL XVIII: time delays of the quadruply lensed quasar WFI2033-4723

We present new measurements of the time delays of WFI2033-4723. The data sets used in this work include 14 years of data taken at the 1.2m Leonhard Euler Swiss telescope, 13 years of data from the SMARTS 1.3m telescope at Las Campanas Observatory and a single year of high-cadence and high-precision monitoring at the MPIA 2.2m telescope. The time delays measured from these different data sets, all taken in the R-band, are in good agreement with each other and with previous measurements from the literature. Combining all the time-delay estimates from our data sets results in Dt_AB = 36.2-0.8+0.7 days (2.1% precision), Dt_AC = -23.3-1.4+1.2 days (5.6%) and Dt_BC = -59.4-1.3+1.3 days (2.2%). In addition, the close image pair A1-A2 of the lensed quasars can be resolved in the MPIA 2.2m data. We measure a time delay consistent with zero in this pair of images. We also explore the prior distributions of microlensing time-delay potentially affecting the cosmological time-delay measurements of WFI2033-4723. There is however no strong indication in our measurements that microlensing time delay is neither present nor absent. This work is part of a H0LiCOW series focusing on measuring the Hubble constant from WFI2033-4723.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Microstructuring of polymer films by femtosecond pulses through optically trapped polystyrene microspheres

We report the laser ablation of polymers by femtosecond (18 and 54 fs) pulses focused by 1 and 3.8 {mu}m diameter spherical microlenses, which are held by optical traps. It is shown that this technique allows one to produce surface structures with lateral dimensions up to {lambda}/6 (125 nm). It is found that the size of the structures depends on the diameter of the microlens; the highest spatial resolution is achieved by using 1 {mu}m diameter microlenses. (extreme light fields and their applications)

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

A STUDY OF GRAVITATIONAL LENS CHROMATICITY WITH THE HUBBLE SPACE TELESCOPE

We report Hubble Space Telescope observations of six gravitational lenses with the Advanced Camera for Surveys. We measured the flux ratios between the lensed images in seven filters from 8140 #Angstrom# to 2200 #Angstrom#. In three of the systems, HE0512-3329, B1600+434, and H1413+117, we were able to construct UV extinction curves partially overlapping the 2175 #Angstrom# feature and characterize the properties of the dust relative to the Galaxy and the Magellanic Clouds. In HE1104-1804, we detect chromatic microlensing and use it to study the physical properties of the quasar accretion disk. For a Gaussian model of the disk exp (- r{sup 2}/2r{sup 2}{sub s}), scaling with wavelength as r{sub s} {proportional_to}{lambda}{sup p}, we estimate r{sub s} ({lambda}3363) = 4{sup +4}{sub -2} (7 {+-} 4) light days and p = 1.1 {+-} 0.6 (1.0 {+-} 0.6) for a logarithmic (linear) prior on r{sub s} . The remaining two systems, FBQ0951+2635 and SBS1520+530, yielded no useful estimates of extinction or chromatic microlensing.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

X-RAY AND OPTICAL FLUX RATIO ANOMALIES IN QUADRUPLY LENSED QUASARS. II. MAPPING THE DARK MATTER CONTENT IN ELLIPTICAL GALAXIES

We present a microlensing analysis of 61 Chandra observations of 14 quadruply lensed quasars. X-ray flux measurements of the individual quasar images give a clean determination of the microlensing effects in the lensing galaxy and thus offer a direct assessment of the local fraction of stellar matter making up the total integrated mass along the lines of sight through the lensing galaxy. A Bayesian analysis of the ensemble of lensing galaxies gives a most likely local stellar fraction of 7%, with the other 93% in a smooth, dark matter component, at a mean impact parameter R{sub c} of 6.6 kpc from the center of the lensing galaxy. We divide the systems into smaller ensembles based on R{sub c} and find that the most likely local stellar fraction varies qualitatively and quantitatively as expected, decreasing as a function of R{sub c} .

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE MAGELLANIC QUASARS SURVEY. II. CONFIRMATION OF 144 NEW ACTIVE GALACTIC NUCLEI BEHIND THE SOUTHERN EDGE OF THE LARGE MAGELLANIC CLOUD

We quadruple the number of quasars known behind the Large Magellanic Cloud (LMC) from 56 (42 in the Optical Gravitational Lensing Experiment (OGLE)-III LMC fields) to 200 by spectroscopically confirming 169 (144 new) quasars from a sample of 845 observed candidates in four {approx}3 deg{sup 2} Anglo-Australian Telescope/AAOmega fields south of the LMC center. The candidates were selected based on their Spitzer mid-infrared colors, X-ray emission, and/or optical variability properties in the database of the OGLE microlensing survey. The contaminating sources can be divided into 115 young stellar objects (YSOs), 17 planetary nebulae (PNe), 39 Be and 24 blue stars, 68 red stars, and 12 objects classed as either YSO/PN or blue star/YSO. There are also 402 targets with either featureless spectra or too low signal-to-noise ratios for source classification. Our quasar sample is 50% (30%) complete at I = 18.6 mag (19.3 mag). The newly discovered active galactic nuclei (AGNs) provide many additional reference points for proper motion studies of the LMC, and the sample includes 10 bright AGNs (I < 18 mag) that are potentially suitable for absorption line studies. Their primary use, however, is for detailed studies of quasar variability, as they all have long-term, high cadence, continuously growing light curves from the microlensing surveys of the LMC. Completing the existing Magellanic Quasars Survey fields in the LMC and Small Magellanic Cloud should yield a sample of {approx}700 well-monitored AGNs, and expanding it to the larger regions covered by the OGLE-IV survey should yield a sample of {approx}3600 AGNs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

X-RAY MONITORING OF GRAVITATIONAL LENSES WITH CHANDRA

We present Chandra monitoring data for six gravitationally lensed quasars: QJ 0158-4325, HE 0435-1223, SDSS 0924+0219, SDSS 1004+4112, HE 1104-1805, and Q 2237+0305. X-ray microlensing variability is detected in all six lenses with high confidence. We furthermore detect energy-dependent microlensing in HE 0435-1223, SDSS 0924+0219, SDSS 1004+4112, and Q 2237+0305. Through a detailed spectral analysis for each lens we find that simple power-law models plus Gaussian emission lines give good fits to the spectra. We detect intrinsic spectral variability in two epochs of Q 2237+0305, and differential absorption between images in QJ 0158-4325 and Q2237+0305. We also detect the Fe K{alpha} emission line in all six lenses, and the Ni XXVII K{alpha} line in two images of Q 2237+0305. The rest-frame equivalent widths of the Fe K{alpha} lines are measured to be 0.4-1.2 keV, significantly higher than those measured in typical active galactic nuclei of similar X-ray luminosities. This suggests that the Fe K{alpha} emission region is more compact or centrally concentrated than the continuum emission region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

MICROLENS TERRESTRIAL PARALLAX MASS MEASUREMENTS: A RARE PROBE OF ISOLATED BROWN DWARFS AND FREE-FLOATING PLANETS

Terrestrial microlens parallax is one of the very few methods that can measure the mass and number density of isolated dark low-mass objects, such as old free-floating planets and brown dwarfs. Terrestrial microlens parallax can be measured whenever a microlensing event differs substantially as observed from two or more well-separated sites. If the lens also transits the source during the event, then its mass can be measured. We derive an analytic expression for the expected rate of such events and then use this to derive two important conclusions. First, the rate is directly proportional to the number density of a given population, greatly favoring low-mass populations relative to their contribution to the general microlensing rate, which further scales as M {sup 1/2} where M is the lens mass. Second, the rate rises sharply as one probes smaller source stars, despite the fact that the probability of transit falls directly with source size. We propose modifications to current observing strategies that could yield a factor of 100 increase in sensitivity to these rare events.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

THE STRUCTURE OF THE X-RAY AND OPTICAL EMITTING REGIONS OF THE LENSED QUASAR Q 2237+0305

We use gravitational microlensing to determine the size of the X-ray and optical emission regions of the quadruple lens system Q 2237+0305. The optical half-light radius, log(R{sub 1/2,V}/cm) = 16.41 {+-} 0.18 (at {lambda}{sub rest} = 2018 A), is significantly larger than the observed soft, log(R{sub 1/2,soft}/cm)=15.76{sup +0.41}{sub -0.34} (1.1-3.5 keV in the rest frame), and hard, log(R{sub 1/2,hard}/cm)=15.46{sup +0.34}{sub -0.29} (3.5-21.5 keV in the rest frame), band X-ray emission. There is weak evidence that the hard component is more compact than the soft, with log(R{sub 1/2,soft}/R{sub 1/2,hard}){approx_equal}0.30{sup +0.53}{sub -0.45}. This wavelength-dependent structure agrees with recent results found in other lens systems using microlensing techniques, and favors geometries in which the corona is concentrated near the inner edge of the accretion disk. While the available measurements are limited, the size of the X-ray emission region appears to be roughly proportional to the mass of the central black hole.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The trends high-contrast imaging survey. IV. The occurrence rate of giant planets around M dwarfs

Doppler-based planet surveys have discovered numerous giant planets but are incomplete beyond several AU. At larger star-planet separations, direct planet detection through high-contrast imaging has proven successful, but this technique is sensitive only to young planets and characterization relies upon theoretical evolution models. Here we demonstrate that radial velocity measurements and high-contrast imaging can be combined to overcome these issues. The presence of widely separated companions can be deduced by identifying an acceleration (long-term trend) in the radial velocity of a star. By obtaining high spatial resolution follow-up imaging observations, we rule out scenarios in which such accelerations are caused by stellar binary companions with high statistical confidence. We report results from an analysis of Doppler measurements of a sample of 111 M-dwarf stars with a median of 29 radial velocity observations over a median time baseline of 11.8 yr. By targeting stars that exhibit a radial velocity acceleration ({sup t}rend{sup )} with adaptive optics imaging, we determine that 6.5% ± 3.0% of M-dwarf stars host one or more massive companions with 1 < m/M{sub J} < 13 and 0 < a < 20 AU. These results are lower than analyses of the planet occurrence rate around higher-mass stars. We find the giant planet occurrence rate is described by a double power law in stellar mass M and metallicity F ≡ [Fe/H] such that f(M,F)=0.039{sub −0.028}{sup +0.056}M{sup 0.8{sub −}{sub 0}{sub .}{sub 9}{sup +{sup 1{sup .{sup 1}}}}}10{sup (3.8±1.2)F}. Our results are consistent with gravitational microlensing measurements of the planet occurrence rate; this study represents the first model-independent comparison with microlensing observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Super-massive planets around late-type stars—the case of OGLE-2012-BLG-0406Lb

Super-Jupiter-mass planets should form only beyond the snow line of host stars. However, the core accretion theory of planetary formation does not predict super-Jupiters forming around low-mass hosts. We present a discovery of a 3.9 ± 1.2 M {sub Jup} mass planet orbiting the 0.59 ± 0.17 M {sub ☉} star using the gravitational microlensing method. During the event, the projected separation of the planet and the star is 3.9 ± 1.0 AU, i.e., the planet is significantly further from the host star than the snow line. This is the fourth such planet discovered using the microlensing technique and challenges the core accretion theory.

79 ASTRONOMY AND ASTROPHYSICS↗