Blended Light Research Articles

Detecting unresolved lensed SNe Ia in LSST using blended light curves

Strongly gravitationally lensed supernovae (LSNe) are promising probes for providing absolute distance measurements using gravitational-lens time delays. Spatially unresolved LSNe offer an opportunity to enhance the sample size for precision cosmology. We predict that there will be approximately three times as many unresolved as resolved LSNe Ia in the Legacy Survey of Space and Time (LSST) by the Rubin Observatory. In this article, we explore the feasibility of detecting unresolved LSNe Ia from a pool of preclassified SNe Ia light curves using the shape of the blended light curves with deep-learning techniques. We find that $ 30<!PCT!>$ unresolved LSNe Ia can be detected with a simple 1D convolutional neural network (CNN) using well-sampled $rizy$-band light curves (with a false-positive rate of $ 3<!PCT!>$). Even when the light curve is well observed in only a single band among $r$, $i$, and $z$, detection is still possible with false-positive rates ranging from $ 4$ to $7<!PCT!>$ depending on the band. Furthermore, we demonstrate that these unresolved cases can be detected at an early stage using light curves up to $ days from the first observation with well-controlled false-positive rates, providing ample opportunity to trigger follow-up observations. Additionally, we demonstrate the feasibility of time-delay estimations using solely LSST-like data of unresolved light curves, particularly for doubles, when excluding systems with low time delays and magnification ratios. However, the abundance of such systems among those unresolved in LSST poses a significant challenge. This approach holds potential utility for upcoming wide-field surveys, and overall results could significantly improve with enhanced cadence and depth in the future surveys.

Localizing Sources of Variability in Crowded TESS Photometry

The Transiting Exoplanet Survey Satellite (TESS) has an exceptionally large plate scale of 21″ px−1, causing most TESS light curves to record the blended light of multiple stars. This creates a danger of misattributing variability observed by TESS to the wrong source, which would invalidate any analysis. We developed a method that can localize the origin of variability on the sky to better than one fifth of a pixel. Given measured frequencies of variability (e.g., from periodogram analysis), we show that the best-fit sinusoid amplitudes to raw light curves extracted from each pixel are distributed in the same way as light from the variable source. The primary assumption of this method is that other nearby stars are not variable at the same frequencies. Essentially, we are using the high frequency resolution of TESS to overcome limitations from its low spatial resolution. We have implemented our method in an open-source Python package, TESS_localize (github.com/Higgins00/TESS-Localize), that determines the location of a variable source on the sky and the most likely Gaia source given TESS pixel data and a set of observed frequencies of variability. Our method utilizes models of the TESS pixel response function, and we characterize systematics in the residuals of fitting these models to data. We find that even stars more than three pixels outside a photometric aperture can produce significant contaminant signals in the extracted light curves. Given the ubiquity of source blending in TESS light curves, verifying the source of observed variability should be a standard step in TESS analyses.

A new method for finding nearby white dwarfs exoplanets and detecting biosignatures

ABSTRACT We demonstrate that the James Webb Space Telescope (JWST) can detect infrared (IR) excess from the blended light spectral energy distribution of spatially unresolved terrestrial exoplanets orbiting nearby white dwarfs. We find that JWST is capable of detecting warm (habitable-zone; Teq = 287 K) Earths or super-Earths and hot (400–1000 K) Mercury analogues in the blended light spectrum around the nearest 15 isolated white dwarfs with 10 h of integration per target using MIRI’s medium-resolution spectrograph (MRS). Further, these observations constrain the presence of a CO2-dominated atmosphere on these planets. The technique is nearly insensitive to system inclination, and thus observation of even a small sample of white dwarfs could place strong limits on the occurrence rates of warm terrestrial exoplanets around white dwarfs in the solar neighbourhood. We find that JWST can also detect exceptionally cold (100–150 K) Jupiter-sized exoplanets via MIRI broad-band imaging at $\lambda = 21\, \mathrm{\mu m}$ for the 34 nearest (<13 pc) solitary white dwarfs with 2 h of integration time per target. Using IR excess to detect thermal variations with orbital phase or spectral absorption features within the atmosphere, both of which are possible with long-baseline MRS observations, would confirm candidates as actual exoplanets. Assuming an Earth-like atmospheric composition, we find that the detection of the biosignature pair O3+CH4 is possible for all habitable-zone Earths (within 6.5 pc; six white dwarf systems) or super-Earths (within 10 pc; 17 systems) orbiting white dwarfs with only 5–36 h of integration using MIRI’s low-resolution spectrometer.

Blended Social Impact Investment Transactions: Why Are They So Complex?

Blended social impact investment (SII) transactions, in which multiple types of capital are combined to support attainment of social impact, are a pervasive, yet not closely examined, feature of the SII market. This paper seeks to describe and understand blended SII transactions through the lens of institutional theory. Specifically, we use the institutional logics theoretical frame to shed light on the implications of combining several institutional logics in SII transactions. Consistent with other SII research, we find that parties to blended SII transactions combine financial/commercial and social welfare logics. However, in blended SII transactions, different combinations of these logics are enacted by different stakeholders in a multi-hybrid-logic structure. As such, we propose that blended SII transactions are hybrids-of-hybrids. We argue that it is this hybrids-of-hybrid characteristic that differentiates blended SII transactions from other forms of SII and increases the potential for significant logical misalignment and resultant conflict and contestation. From a business ethics perspective, blended SII transactions cast light on the critical and often unrecognized role that grants and concessionary capital frequently play in enabling SII in not-for-profit, charitable ventures. We speculate that this can distort understanding of SII with adverse implications at the transaction and field levels.

Lens parameters for Gaia18cbf – a long gravitational microlensing event in the Galactic plane

Context. The timescale of a microlensing event scales as a square root of a lens mass. Therefore, long-lasting events are important candidates for massive lenses, including black holes. Aims. Here, we present the analysis of the Gaia18cbf microlensing event reported by the Gaia Science Alerts system. It exhibited a long timescale and features that are common for the annual microlensing parallax effect. We deduce the parameters of the lens based on the derived best fitting model. Methods. We used photometric data collected by the Gaia satellite as well as the follow-up data gathered by the ground-based observatories. We investigated the range of microlensing models and used them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using a known mass-brightness relation, we determined how likely it is that the lens is a main-sequence (MS) star. Results. This event is one of the longest ever detected, with the Einstein timescale of tE = 491.41−84.94+128.31 days for the best solution and tE = 453.74−105.74+178.69 days for the second best. Assuming Galaxy priors, this translates to the most probable lens masses of ML = 2.65−1.48+5.09 M⊙ and ML = 1.71−1.06+3.78 M⊙, respectively. The limits on the blended light suggest that this event was most likely not caused by a MS star, but rather by a dark remnant of stellar evolution.

Single-lens mass measurement in the high-magnification microlensing event Gaia19bld located in the Galactic disc

Context. Microlensing provides a unique opportunity to detect non-luminous objects. In the rare cases that the Einstein radius θE and microlensing parallax πE can be measured, it is possible to determine the mass of the lens. With technological advances in both ground- and space-based observatories, astrometric and interferometric measurements are becoming viable, which can lead to the more routine determination of θE and, if the microlensing parallax is also measured, the mass of the lens. Aims. We present the photometric analysis of Gaia19bld, a high-magnification (A ≈ 60) microlensing event located in the southern Galactic plane, which exhibited finite source and microlensing parallax effects. Due to a prompt detection by the Gaia satellite and the very high brightness of I = 9.05 mag at the peak, it was possible to collect a complete and unique set of multi-channel follow-up observations, which allowed us to determine all parameters vital for the characterisation of the lens and the source in the microlensing event. Methods. Gaia19bld was discovered by the Gaia satellite and was subsequently intensively followed up with a network of ground-based observatories and the Spitzer Space Telescope. We collected multiple high-resolution spectra with Very Large Telescope (VLT)/X-shooter to characterise the source star. The event was also observed with VLT Interferometer (VLTI)/PIONIER during the peak. Here we focus on the photometric observations and model the light curve composed of data from Gaia, Spitzer, and multiple optical, ground-based observatories. We find the best-fitting solution with parallax and finite source effects. We derived the limit on the luminosity of the lens based on the blended light model and spectroscopic distance. Results. We compute the mass of the lens to be 1.13 ± 0.03 M⊙ and derive its distance to be 5.52−0.64+0.35 kpc. The lens is likely a main sequence star, however its true nature has yet to be verified by future high-resolution observations. Our results are consistent with interferometric measurements of the angular Einstein radius, emphasising that interferometry can be a new channel for determining the masses of objects that would otherwise remain undetectable, including stellar-mass black holes.

Wireless Controlled Wide Range Tuneable CCT Lighting System Using Three Component Colour Mixing

This paper proposes a novel approach of wireless controlled, tenable correlated colour temperature (CCT) lighting system with high colour rendering index (CRI) using the concept of colour mixing. Using Grassmann’s colour mixing theory, phosphor coated warm white LED source (CCT 2800 K) is mixed with the blue and green LED light sources to meet the requirement of high CRI and high value of red object identification parameter R9. A detailed mathematical formulation is derived for easy controlling of variable CCT and illuminance and a flowchart of wireless control scheme is incorporated and experimentally validated in this article. As a result, the locus of the blended light source is very close to the Planckian locus on CIE1931 chromaticity diagram with a minimum uv D value of +0.0005. This proposed system provides a very wide range CCT starting from 2800 K to 15000 K with a high CRI value of 94 at CCT 5000 K. Another feature of this blended light source is the true colour identification parameter of red object (R9), which is also increased to 93 at CCT 8000 K. This system has very wide application in industries like textile, food processing etc., in museum, art gallery, and medical application like surgical lighting for its high CRI and R9 value with wide range of CCTs.

An Earth-mass planet in a time of COVID-19: KMT-2020-BLG-0414Lb

We report the discovery of KMT-2020-BLG-0414Lb, with a planet-to-host mass ratio q 2 = 0.9–1.2 × 10−5 = 3–4 ⊕ at 1σ, which is the lowest mass-ratio microlensing planet to date. Together with two other recent discoveries (4 ≲ q/q ⊕ ≲ 6), it fills out the previous empty sector at the bottom of the triangular (log s, log q) diagram, where s is the planet-host separation in units of the angular Einstein radius θE. Hence, these discoveries call into question the existence, or at least the strength, of the break in the mass-ratio function that was previously suggested to account for the paucity of very low-q planets. Due to the extreme magnification of the event, A max ∼ 1450 for the underlying single-lens event, its light curve revealed a second companion with q 3 ∼ 0.05 and |log s 3| ∼ 1, i.e., a factor ∼ 10 closer to or farther from the host in projection. The measurements of the microlens parallax π E and the angular Einstein radius θE allow estimates of the host, planet and second companion masses, (M 1, M 2, M 3) ∼ (0.3 M ⊙, 1.0 M ⊕, 17 MJ ), the planet and second companion projected separations, (a ⊥,2, a ⊥,3) ∼ (1.5, 0.15 or 15) au, and system distance D L ∼ 1 kpc. The lens could account for most or all of the blended light (I ∼ 19.3) and so can be studied immediately with high-resolution photometric and spectroscopic observations that can further clarify the nature of the system. The planet was found as part of a new program of high-cadence follow-up observations of high-magnification events. The detection of this planet, despite the considerable difficulties imposed by COVID-19 (two KMT sites and OGLE were shut down), illustrates the potential utility of this program.

EFFECTS OF BLENDED RICE BRAN OIL NEPTUNE LIGHT ON THE DYSLIPIDEMIA AMONG OVERWEIGHT AND OBESE ADULTS

Objective: To assessment total cholesterol (TC), LDL-C, HDL, and triglyceride (TG) concentrations changed after using blended rice bran oil Neptune Light among dyslipidemia adults at different categories of obese. Methods: Forty-one adults with dual conditions (dyslipidemia and overweight/obese) from 40 to 60 years old received a 600-700 kcal meal contained 20g/day Neptune Light rice bran oil for 60 days. Fasting blood samples and BMI was collected at baseline and every 30 days of trial. Results: Total cholesterol (TC), LDL-C and TG level declined by 0.5mmol/L (8.5%); 0.49 mmol/L (23.7%) and 0.55 mmol/L (32.0%), respectively after 60 days of intervention. The highest reduction of TC and TG was showed in the pre-obesity group, while the highest LDL-C reduction was shown in the obesity class II group. Conclusion: Using Neptune Light rice bran oil reduced TC, LDL-C and triglyceride level in overweight/obese adults from 40-60 years old after 60 days of intervention.

Low cost, high color rendition, CCT variable lighting system based on W-G-B LED

This article proposes a novel approach of tunable correlated color temperature (CCT) lighting system with high color rendition using three component color mixing concept. Using Grassmann’s color mixing theory, phosphor coated warm white LED source (CCT 2800 K) is mixed with the blue (467 nm) and green (527 nm) LED light sources and a detailed mathematical formulation is derived for easy controlling of variable CCT and experimentally validated in this article. As a result, the locus of the blended light source is very close to the Planckian locus on Commission Internationale de l’Eclairage (CIE) 1931 chromaticity diagram. The generated color of the light sources is evaluated by both CIE color rendering index (CRI) method and Illuminating Engineering Society (IES) TM-30-18 method. This proposed system provides a wide range of CCTs starting from 2800 K to 7500 K with a very high CRI (CIE Ra) value of 94, color fidelity index (IES Rf) score of around 85 and color gamut index (IES Rg) of 95. As this system uses only three color component, the cost of this system is comparatively low with respect to other high CRI, tunable CCT lighting system available in market.

KMT-2019-BLG-0842Lb: A Cold Planet below the Uranus/Sun Mass Ratio

Abstract We report the discovery of a cold planet with a very low planet/host mass ratio of q = (4.09 ± 0.27) × 10−5, which is similar to the ratio of Uranus/Sun (q = 4.37 × 10−5) in the solar system. The Bayesian estimates for the host mass, planet mass, system distance, and planet–host projected separation are M host = 0.76 ± 0.40M ⊙, M planet = 10.3 ± 5.5M ⊕, D L = 3.3 ± 1.3 kpc, and a ⊥ = 3.3 ± 1.4 au, respectively. The consistency of the color and brightness expected from the estimated lens mass and distance with those of the blend suggests the possibility that the most blended light comes from the planet host, and this hypothesis can be established if high-resolution images are taken during the next (2020) bulge season. We discuss the importance of conducting optimized photometry and aggressive follow-up observations for moderately or very high magnification events to maximize the detection rate of planets with very low mass ratios.

OGLE-2018-BLG-1269Lb: A Jovian Planet with a Bright I = 16 Host

Abstract We report the discovery of a planet in the microlensing event OGLE-2018-BLG-1269 with a planet–host mass ratio q ∼ 6 × 10−4, i.e., 0.6 times smaller than the Jupiter/Sun mass ratio. Combined with the Gaia parallax and proper motion, a strong one-dimensional constraint on the microlens parallax vector allows us to significantly reduce the uncertainties of lens physical parameters. A Bayesian analysis that ignores any information about light from the host yields that the planet is a cold giant orbiting a Sun-like star at a distance of . The projected planet–host separation is . Using Gaia astrometry, we show that the blended light lies from the host and therefore must be either the host star or a stellar companion to the host. An isochrone analysis favors the former possibility at >99.6%. The host is therefore a subgiant. For host metallicities in the range of , the host and planet masses are then in the range of and , respectively. Low host metallicities are excluded. The brightness and proximity of the lens make the event a strong candidate for spectroscopic follow-up both to test the microlensing solution and to further characterize the system.

Spitzer + VLTI-GRAVITY Measure the Lens Mass of a Nearby Microlensing Event

Abstract We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555 (Kojima-1). We measure the microlens parallax vector using Spitzer and ground-based light curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this determination with the angular Einstein radius measured by VLTI-GRAVITY observations, we find that the lens is a star with mass at a distance D L = 429 ± 21 pc. We find that the blended light basically all comes from the lens. The lens-source proper motion is , so with currently available adaptive-optics instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry + satellite-parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes.

KMT-2017-BLG-0165Lb: A Super-Neptune-mass Planet Orbiting a Sun-like Host Star

Abstract We report the discovery of a low-mass-ratio planet (q = 1.3 × 10−4), i.e., 2.5 times higher than the Neptune/Sun ratio. The planetary system was discovered from the analysis of the KMT-2017-BLG-0165 microlensing event, which has an obvious short-term deviation from the underlying light curve produced by the host of the planet. Although the fit improvement with the microlens parallax effect is relatively low, one component of the parallax vector is strongly constrained from the light curve, making it possible to narrow down the uncertainties of the lens physical properties. A Bayesian analysis yields that the planet has a super-Neptune mass orbiting a Sun-like star located at 4.5 kpc. The blended light is consistent with these host properties. The projected planet-host separation is , implying that the planet is located outside the snow line of the host, i.e., a sl ∼ 2.1 au. KMT-2017-BLG-0165Lb is the sixteenth microlensing planet with mass ratio q < 3 × 10−4. Using the fifteen of these planets with unambiguous mass-ratio measurements, we apply a likelihood analysis to investigate the form of the mass-ratio function in this regime. If we adopt a broken power law for the form of this function, then the break is at q br ≃ 0.55 × 10−4, which is much lower than previously estimated. Moreover, the change of the power-law slope, ζ > 3.3, is quite severe. Alternatively, the distribution is also suggestive of a pileup of planets at Neptune-like mass ratios, below which there is a dramatic drop in frequency.

A modified version of the kernel-driven model for correcting the diffuse light of ground multi-angular measurements

When using the kernel-driven bidirectional reflectance distribution function (BRDF) model to process multi-angular measurements, the input multi-angular measurements must be corrected for atmospheric effects. However, in current databases, a significant number of ground-based multi-angular measurements contain either no corrections or only approximate corrections for atmospheric effects. Thus, the blended diffuse light in the total incident irradiance will result in considerable smoothing of the reflectance anisotropy retrieved by the kernel-driven model unless an atmospheric correction process is conducted. In this study, we propose a diffuse-light correction (DLC) form of the kernel-driven model that improves its ability to process multi-angular measurements blended with hemispherical diffuse light. The DLC form of the kernel-driven model can be used to retrieve the intrinsic reflectance anisotropy of the observed target from atmospheric-uncorrected multi-angular measurements. This study used multi-angular data simulated by the PROSAIL and Radiosity Applicable to Porous IndiviDual objects (RAPID) BRDF model, atmospheric-corrected Polarization and Directionality of the Earth's Reflectances (POLDER), Cloud Absorption Radiometer (CAR) multi-angular measurements and their simulated data based on the Second Simulation of the Satellite Signal in the Solar Spectrum (6S) tools to validate the effectiveness of the DLC form of the kernel-driven model. The results indicated that the reflectance factors directly retrieved by the kernel-driven model are considerably smoothed by the blended diffuse light, especially in hotspot regions. Even under clear and cloudless sky conditions, the retrieved hotspot reflectance in the red band is still underestimated by an average of 9.25%, 7.72%, 11.0% and 13.8% for the PROSAIL, RAPID, POLDER and CAR data, respectively. In contrast, the hotspot reflectance retrieved by the DLC form of the kernel-driven model is very close to the intrinsic reflectance anisotropy of the targets; the average relative error of the DLC form of the kernel-driven model is only 1.99%, 1.50%, 4.57% and 3.42%, respectively. Although the reflectance reconstructed by the DLC form of the kernel-driven model in the hotspot region represents a considerable improvement compared with the reflectance retrieved by the original kernel-driven model, its improvement on the root mean square error (RMSE) and the bias of the entire datasets is not very apparent. Using the DLC form of the kernel-driven model can significantly improve the ability of the kernel-driven model to process multi-angular measurements blended with hemispherical diffuse irradiance.

Combining Spitzer Parallax and Keck II Adaptive Optics Imaging to Measure the Mass of a Solar-like Star Orbited by a Cold Gaseous Planet Discovered by Microlensing

Abstract To obtain accurate mass measurements for cold planets discovered by microlensing, it is usually necessary to combine light curve modeling with at least two lens mass–distance relations. The physical parameters of the planetary system OGLE-2014-BLG-0124L have been constrained thanks to accurate parallax effect between ground-based and simultaneous space-based Spitzer observations. Here, we resolved the source+lens star from sub-arcsecond blends in H-band using adaptive optics (AO) observations with NIRC2 mounted on Keck II telescope. We identify additional flux, coincident with the source to within 160 mas. We estimate the potential contributions to this blended light (chance-aligned star, additional companion to the lens or to the source) and find that 85% of the NIR flux is due to the lens star at H L = 16.63 ± 0.06 and K L = 16.44 ± 0.06. We combined the parallax constraint and the AO constraint to derive the physical parameters of the system. The lensing system is composed of a mid-late type G main sequence star of M L = 0.9 ± 0.05 M ⊙ located at D L = 3.5 ± 0.2 kpc in the Galactic disk. Taking the mass ratio and projected separation from the original study leads to a planet of M p = 0.65 ± 0.044 M Jupiter at 3.48 ± 0.22 au. Excellent parallax measurements from simultaneous ground-space observations have been obtained on the microlensing event OGLE-2014-BLG-0124, but it is only when they are combined with ∼30 minutes of Keck II AO observations that the physical parameters of the host star are well measured.

MOA-2011-BLG-028Lb: A NEPTUNE-MASS MICROLENSING PLANET IN THE GALACTIC BULGE*

ABSTRACT We present the discovery of a Neptune-mass planet orbiting a 0.8 ± 0.3 M ⊙ 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 ) × 10 − 4 , which indicates that the mass of the planet is 12–60 Earth masses. The lensing system is located at 7.3 ± 0.7 kpc away from the Earth near the direction of 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 HIGH FALSE POSITIVE RATE FORKEPLERPLANETARY CANDIDATES OF GIANT STARS USING ASTERODENSITY PROFILING

Asterodensity Profiling (AP) is a relatively new technique for studying transit light curves. By comparing the mean stellar density derived from the transit light curve to that found through some independent method, AP provides information on several useful properties such as orbital eccentricity and blended light. We present an AP survey of 41 Kepler Objects of Interest (KOIs), with a single transiting candidate, for which the target star's mean stellar density has been measured using asteroseismology. The ensemble distribution of the AP measurements for the 31 dwarf stars in our sample shows excellent agreement with the spread expected if the KOIs were genuine and have realistic eccentricities. In contrast, the same test for the 10 giants in our sample reveals significant incompatibility at 4$\sigma$ confidence. Whilst extreme eccentricities could be invoked, this hypothesis requires four of the KOIs to contact their host star at periastron passage, including the recently claimed confirmation of Kepler-91b. After carefully examining several hypotheses, we conclude that the most plausible explanation is that the transiting objects orbit a different star to that measured with asteroseismology - cases we define as false-positives. Based on the AP distribution, we estimate a false positive rate for Kepler's giant stars with a single transiting object of FPR$\simeq70\pm30$%.

CHARACTERIZING LOW-MASS BINARIES FROM OBSERVATION OF LONG-TIMESCALE CAUSTIC-CROSSING GRAVITATIONAL MICROLENSING EVENTS

Despite astrophysical importance of binary star systems, detections are limited to those located in small ranges of separations, distances, and masses and thus it is necessary to use a variety of observational techniques for a complete view of stellar multiplicity across a broad range of physical parameters. In this paper, we report the detections and measurements of 2 binaries discovered from observations of microlensing events MOA-2011-BLG-090 and OGLE-2011-BLG-0417. Determinations of the binary masses are possible by simultaneously measuring the Einstein radius and the lens parallax. The measured masses of the binary components are 0.43 $M_{\odot}$ and 0.39 $M_{\odot}$ for MOA-2011-BLG-090 and 0.57 $M_{\odot}$ and 0.17 $M_{\odot}$ for OGLE-2011-BLG-0417 and thus both lens components of MOA-2011-BLG-090 and one component of OGLE-2011-BLG-0417 are M dwarfs, demonstrating the usefulness of microlensing in detecting binaries composed of low-mass components. From modeling of the light curves considering full Keplerian motion of the lens, we also measure the orbital parameters of the binaries. The blended light of OGLE-2011-BLG-0417 comes very likely from the lens itself, making it possible to check the microlensing orbital solution by follow-up radial-velocity observation. For both events, the caustic-crossing parts of the light curves, which are critical for determining the physical lens parameters, were resolved by high-cadence survey observations and thus it is expected that the number of microlensing binaries with measured physical parameters will increase in the future.

Minimizing follow-up for space-based transit surveys using full lightcurve analysis

One of the biggest challenges facing large transit surveys is the elimination of false-positives from the vast number of transit candidates. We investigate to what extent information from the lightcurves can identify blend scenarios and eliminate them as planet candidates, to significantly decrease the amount of follow-up observing time required to identify the true exoplanet systems. If a lightcurve has a sufficiently high signal-to-noise ratio, a distinction can be made between the lightcurve of a stellar binary blended with a third star and the lightcurve of a transiting exoplanet system. We perform simulations to determine what signal-to-noise level is required to make the distinction between blended and non-blended systems as function of transit depth and impact parameter. Subsequently we test our method on real data from the first IRa01 field observed by the CoRoT satellite, concentrating on the 51 candidates already identified by the CoRoT team. About 70% of the planet candidates in the CoRoT IRa01 field are best fit with an impact parameter of b>0.85, while less than 15% are expected in this range considering random orbital inclinations. By applying a cut at b<0.85, meaning that ~15% of the potential planet population would be missed, the candidate sample decreases from 41 to 11. The lightcurves of 6 of those are best fit with such low host star densities that the planet-to-star size ratii imply unrealistic planet radii of R>2RJup. Two of the five remaining systems, CoRoT1b and CoRoT4b, have been identified as planets by the CoRoT team, for which the lightcurves alone rule out blended light at 14% (2sigma) and 31% (2sigma). We propose to use this method on the Kepler database to study the fraction of real planets and to potentially increase the efficiency of follow-up.