Astrometric microlensing

Nucita, A. A.; Paolis, F. De; Ingrosso, G.; Giordano, M.; Manni, L.

doi:10.1142/s0218271817410152

Cited by 31 publications

(7 citation statements)

References 53 publications

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“…Note that the components of the GAIA DR2 proper motions are µ α * = µ α cos(δ) and µ δ (Luri et al 2018). This measurement is also affected by the blending and, assuming the blend light is coming only from the lens, the reported proper motion is the proper motion of the photocenter, similarly to the astrometric microlensing (Dominik & Sahu 2000;Nucita et al 2017):…”

Section: Predictions With Gaia Dr2 Proper Motionsmentioning

confidence: 99%

Reconciling the Predictions of Microlensing Analysis with Radial Velocity Measurements for OGLE-2011-BLG-0417

Bachelet

Beaulieu

Boisse

et al. 2018

ApJ

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Microlensing is able to reveal multiple body systems located several kilo-parsec away from the Earth. Since it does not require the measurement of light from the lens, microlensing is sensitive to a range of objects from free-floating planets to stellar black holes. But if the lens emits enough light, the microlensing model predictions can be tested with high-resolution imaging and/or radial velocity methods. Such follow-up was done for the microlensing event OGLE-2011-BLG-0417, which was expected to be a close by (≤ 1 kpc), lowmass (∼ 0.8M ) binary star with a period P ∼ 1.4 yr. The spectroscopic follow-up observations conducted with the VLT did not measure any variation in the radial velocity, in strong contradiction with the published microlensing model. In the present work, we remodel this event and find a simpler model in agreement with all the available measurements, including the recent GAIA DR2 parallax constraints. We also present a new way to distinguish degenerate models by using the GAIA DR2 proper motions. This work stresses the importance of thorough microlensing modeling, especially with the horizon of the WFIRST and the Euclid microlensing space missions.

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Section: Predictions With Gaia Dr2 Proper Motionsmentioning

confidence: 99%

Reconciling the Predictions of Microlensing Analysis with Radial Velocity Measurements for OGLE-2011-BLG-0417

Bachelet

Beaulieu

Boisse

et al. 2018

ApJ

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“…To break this degeneracy, second-order effects, as the finite source effects and the parallax effect, can be considered. Also, it is well known that a gravitational microlensing event gives rise to an astrometric shift of the source, which may be extremely useful to break, at least partially, the parameter degeneracy problem in microlensing observations (Hamolli et al (2019), Nucita et al (2017)).…”

Section: Microlensing Basicsmentioning

confidence: 99%

Gravitational microlensing constraints on primordial black holes by Euclid

Hamolli,

Hafizi,

De Paolis

et al. 2021

Preprint

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Primordial black holes (PBHs) may form in the early stages of the Universe via the collapse of large density perturbations. Depending on the formation mechanism, PBHs may exist and populate today the galactic halos and have masses in a wide range, from about 10 −14 M ⊙ up to thousands, or more, of solar masses.Gravitational microlensing is the most robust and powerful method to constrain primordial black holes (PBHs), since it does not require that the lensing objects be directly visible. We calculate the optical depth and the rate of microlensing events caused by PBHs eventually distributed in the Milky Way halo, towards some selected directions of observation. Then we discuss the capability of Euclid, a space-based telescope which might perform microlensing observations at the end of its nominal mission, to probe the PBH populations in the Galactic halo.

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“…It is well known that, in addition to the photometric lightcurve, a gravitational microlensing event gives rise also to an astrometric deflection, as the event unfolds. This is because the images produced by the lens are not symmetrically distributed, leading to a typical elliptic pattern traced by the centroid, which was studied by many authors [45][46][47][48][49]. The centroid of the image pair can be defined as the average position of the + and − images weighted by the associated magnifications [50,51]:…”

Section: Basics Of Astrometric Microlensingmentioning

confidence: 99%

Free-floating planets in the Milky Way

et al. 2019

Self Cite

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Gravitational microlensing is a powerful method to search for and characterize exoplanets, and it was first proposed by Paczyński in 1986. We provide a brief historical excursus of microlensing, especially focused on the discoveries of free-floating planets (FFPs) in the Milky Way. We also emphasize that, thanks to the technological developments, it will allow to estimate the physical parameters (in particular the mass and distance) of FFPs towards the center of our Galaxy, through the measure of the source finite radius, Earth or satellite parallax, and/or astrometric effects.Mathematics Subject Classification 85-xx · 85-08 IntroductionDiscovery of the extrasolar planets in our Galaxy is one of the most discussed issues in the scientific community. These objects are outside our solar system and have masses smaller than about 0.01M . Their detection is being achieved using different methods and, until now, we have 3824 confirmed exoplanes (see the website http://exoplanet.eu). Most exoplanets are discovered by the Transit method (∼ 74%) and by Radial Velocity method (∼ 20%). A few exoplanets have been detected using the Direct Imaging technique. Until now, only ∼ 2% of exoplanets have been detected through gravitational microlensing.In recent years, several unbound objects with mass possibly as small as a few times that of Jupiter (M J = 9.5 × 10 −4 M ) have been found in many young star-forming region using infrared imaging surveys [1]. These objects are called free-floating planets or also rogue planets, nomads, or orphan planets (see [2] and references therein). Examples of objects of this kind are WISE 0855-0714, about 2.4 pc away from the Earth [3], and Cha 110913-773444 in the Chamaeleon I star-forming region at a distance of about 160 pc. It is difficult to find this kind of objects by infrared imaging at large distances, so we need the development of alternative methods to search for them. The origin of the FFPs is doubtful, and their formation mechanism remains an open theoretical question in astrophysics. One possibility is that they originally formed around a host star and then scattered out from orbit. A second option is that they may form on their own through gas cloud direct collapse, similarly to star formation.Paczyński [4] first envisaged the search of Galactic dark matter in compact form using gravitational lensing method, which happens when a massive object passes close enough to the line of sight to a distant source star. Since the angular separation of the lensed images are of the order of microarcseconds, such phenomena are often called microlensing [5,6]. In his calculations, Paczyński showed that the chance (or optical depth) of a massive object in the Galactic halo to serve as a lens and magnify a background star in nearby galaxy is 10 −6 . Also, he suggested that, based on modern instruments, we could be able to catch such microlensing events by monitoring a dense stellar field with several millions of stars simultaneously. Therefore, several groundbased experiments such as MACHO (Massiv...

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Astrometric microlensing

Cited by 31 publications

References 53 publications

Reconciling the Predictions of Microlensing Analysis with Radial Velocity Measurements for OGLE-2011-BLG-0417

Reconciling the Predictions of Microlensing Analysis with Radial Velocity Measurements for OGLE-2011-BLG-0417

Gravitational microlensing constraints on primordial black holes by Euclid

Free-floating planets in the Milky Way

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