microlensing binaries with candidate brown dwarf companions
... phenomenon wherein the brightness of a star is magnified by the bending of light caused by the gravity of an intervening object (lens) between the background star (source) and an observer. Since the phenomenon occurs regardless of the lens brightness, microlensing was proposed to detect dark compone ...
... phenomenon wherein the brightness of a star is magnified by the bending of light caused by the gravity of an intervening object (lens) between the background star (source) and an observer. Since the phenomenon occurs regardless of the lens brightness, microlensing was proposed to detect dark compone ...
a space smile - Physique chimie Dijon
... agency, in which we learned: "Galaxy clusters are the most massive structures in the Universe and exert such a powerful gravitational pull that they warp the spacetime around them and act as cosmic lenses which can magnify, distort and bend the light behind them. This phenomenon, crucial to many of ...
... agency, in which we learned: "Galaxy clusters are the most massive structures in the Universe and exert such a powerful gravitational pull that they warp the spacetime around them and act as cosmic lenses which can magnify, distort and bend the light behind them. This phenomenon, crucial to many of ...
CHAPTER-17 Light and Image Formation
... E6: A positive lens has a focal length of 12 cm. An object is located at a distance of 3 cm from the lens. a. How far from the lens is the image? b. State three properties of the image? (real/virtual, erect/inverted, magnified/reduced) c. Draw a ray diagram and show the image formation. ...
... E6: A positive lens has a focal length of 12 cm. An object is located at a distance of 3 cm from the lens. a. How far from the lens is the image? b. State three properties of the image? (real/virtual, erect/inverted, magnified/reduced) c. Draw a ray diagram and show the image formation. ...
Dark matter in the Galactic Halo Rotation curve (i.e. the orbital
... there is too much dark matter for it all to be baryons, must be largely non-baryonic. On galaxy scales no such simple argument exists. Individual types of dark matter can be constrained using various indirect arguments, but only direct probe is via gravitational lensing. ...
... there is too much dark matter for it all to be baryons, must be largely non-baryonic. On galaxy scales no such simple argument exists. Individual types of dark matter can be constrained using various indirect arguments, but only direct probe is via gravitational lensing. ...
CRAZY ILLUSIONS can be created by the power of gravity. Objects
... a star does the lensing, for example, the images are so close together that even the best telescopes cannot resolve them. This so-called microlensing effect is nonetheless measurable. Because the star is moving, the lens configuration— and therefore the magnification— changes over time. If observers ...
... a star does the lensing, for example, the images are so close together that even the best telescopes cannot resolve them. This so-called microlensing effect is nonetheless measurable. Because the star is moving, the lens configuration— and therefore the magnification— changes over time. If observers ...
(eo211) 6. Convex Lens Focal Length Measurement: Conjugate
... The key equation here is the Gaussian Lens formula. For D>4f there are two real and positive solutions to the equation: ...
... The key equation here is the Gaussian Lens formula. For D>4f there are two real and positive solutions to the equation: ...
Cosmological Applications of Gravitational Lensing
... Dark Matter Studies Large Scale Structure Inhomogeneities up to 50 100 Mpc elliptical distortions in images of distant sources and changes in apparent luminosities Discovery of faint blue galaxy population provides a potential way to study these effects If cold dark matter cosmology is co ...
... Dark Matter Studies Large Scale Structure Inhomogeneities up to 50 100 Mpc elliptical distortions in images of distant sources and changes in apparent luminosities Discovery of faint blue galaxy population provides a potential way to study these effects If cold dark matter cosmology is co ...
CHAPTER-17 Light and Image Formation
... E6: A positive lens has a focal length of 12 cm. An object is located at a distance of 3 cm from the lens. a. How far from the lens is the image? b. State three properties of the image? (real/virtual, erect/inverted, magnified/reduced) c. Draw a ray diagram and show the image formation. ...
... E6: A positive lens has a focal length of 12 cm. An object is located at a distance of 3 cm from the lens. a. How far from the lens is the image? b. State three properties of the image? (real/virtual, erect/inverted, magnified/reduced) c. Draw a ray diagram and show the image formation. ...
OB390 and the new microlensing planets
... percent) on the light curve of a gravitationally lensed bulge star in about 20 percent of the microlensing events. » Griest & Safizadeh 1998 « We show that by focusing on high-magnification events, the probability of detecting planets of Jupiter mass or greater in the lensing zone ...
... percent) on the light curve of a gravitationally lensed bulge star in about 20 percent of the microlensing events. » Griest & Safizadeh 1998 « We show that by focusing on high-magnification events, the probability of detecting planets of Jupiter mass or greater in the lensing zone ...
All About MACHO
... speeds of objects. For example, in large clusters of more than a thousand galaxies, the speeds of those galaxies imply a mass of dark matter that is 10–30 times greater than that of visible stars and gas. In these systems there are other ways to measure the depth of the gravitational potential well, ...
... speeds of objects. For example, in large clusters of more than a thousand galaxies, the speeds of those galaxies imply a mass of dark matter that is 10–30 times greater than that of visible stars and gas. In these systems there are other ways to measure the depth of the gravitational potential well, ...
DM in the Galaxy - University of Oxford
... • Proper motions essential: vlos ! vr, vt! r¹ • Need also dº/dr for population • Wilkinson & Evans (99): ...
... • Proper motions essential: vlos ! vr, vt! r¹ • Need also dº/dr for population • Wilkinson & Evans (99): ...
www-thphys.physics.ox.ac.uk
... • Baryons drive towards axisymmetry • Uncertain predictions • Should be able to probe with tidal streams • Conflicting results to date • SDSS and Leiden-Argentine-Bonn surveys should transform the situation ...
... • Baryons drive towards axisymmetry • Uncertain predictions • Should be able to probe with tidal streams • Conflicting results to date • SDSS and Leiden-Argentine-Bonn surveys should transform the situation ...
WIMPs versus MACHOS
... governs the majestic rotation of galaxies seeds the evolution of cosmic structures determines the fate of the Universe Understanding the nature and distribution of Dark Matter is one of the most pressing open questions in the physical sciences today ...
... governs the majestic rotation of galaxies seeds the evolution of cosmic structures determines the fate of the Universe Understanding the nature and distribution of Dark Matter is one of the most pressing open questions in the physical sciences today ...
Dai, S - PulsarAstronomy.net
... directly measured only in binaries; no isolated stellar-mass BH has been detected unambiguously within our Galaxy. We have underway a large, 3-year HST program (192 orbits) designed to detect ...
... directly measured only in binaries; no isolated stellar-mass BH has been detected unambiguously within our Galaxy. We have underway a large, 3-year HST program (192 orbits) designed to detect ...
Astrophysics in the Time Domain: Results and lessons
... a crude measure of the event’s wavelength spectrum – The ratios for “vanilla” stars (i.e. microlensing) differ from supernovae ...
... a crude measure of the event’s wavelength spectrum – The ratios for “vanilla” stars (i.e. microlensing) differ from supernovae ...
WIMPs vs. MACHOS: What's the Matter?
... • The trick is distinguishing microlensing from intrinsic stellar variability • More than 200 events seen towards Galactic center • Valuable new tool for astrophysics ...
... • The trick is distinguishing microlensing from intrinsic stellar variability • More than 200 events seen towards Galactic center • Valuable new tool for astrophysics ...
The Gravitational Microlensing Planet Search Technique from
... background imply significantly poorer photometric accuracy even for relatively uncrowded stars such as the example shown above. Nevertheless, there are some events for which the signals of Earth-mass planets are large enough to be detected. Our simulations of a survey from a 2.5m wide-field imaging ...
... background imply significantly poorer photometric accuracy even for relatively uncrowded stars such as the example shown above. Nevertheless, there are some events for which the signals of Earth-mass planets are large enough to be detected. Our simulations of a survey from a 2.5m wide-field imaging ...
Turning AGN Microlensing From a Curiosity Into a Tool
... • Computationally challenging to allow stars to move – we need ~3 GByte to analyze a systems at 2 wavelengths with static patterns, but ~300 GBytes if we allow the stars to move and need an animated sequence of patterns. Probably doable on shared memory machines (and we have experimented with this), ...
... • Computationally challenging to allow stars to move – we need ~3 GByte to analyze a systems at 2 wavelengths with static patterns, but ~300 GBytes if we allow the stars to move and need an animated sequence of patterns. Probably doable on shared memory machines (and we have experimented with this), ...
Microlensing - Caltech Astronomy
... lens moves across the Earth–source line and the amount of brightening changes. Typically the source will appear to brighten, reach a maximum and then fade symmetrically back to normal over the course of a few weeks or months; this is called a ‘microlensing event’. The major application of microlensi ...
... lens moves across the Earth–source line and the amount of brightening changes. Typically the source will appear to brighten, reach a maximum and then fade symmetrically back to normal over the course of a few weeks or months; this is called a ‘microlensing event’. The major application of microlensi ...
Powerpoint file
... Planets discovered using the transit (blue), RV (black), and microlensing (magenta) techniques are shown as individual points, with OGLE-2005-BLG-169Lb displayed as an open symbol. Solar system planets are indicated by their initials for comparison. ...
... Planets discovered using the transit (blue), RV (black), and microlensing (magenta) techniques are shown as individual points, with OGLE-2005-BLG-169Lb displayed as an open symbol. Solar system planets are indicated by their initials for comparison. ...
Blue and Grey
... Microlensing occurs when a massive foreground object passes between the observer and the source being observed. The Einstein angle is angular radius of the Einstein ring in the event of perfect alignment given by ...
... Microlensing occurs when a massive foreground object passes between the observer and the source being observed. The Einstein angle is angular radius of the Einstein ring in the event of perfect alignment given by ...
Lecture 10
... from the source star (2) For u = 0, apparently infinite magnification! In reality, finite size of source limits the peak amplification (3) Rule of thumb: significant magnification requires an impact parameter smaller than the Einstein ring radius (4) Microlensing is achromatic – all wavelengths affe ...
... from the source star (2) For u = 0, apparently infinite magnification! In reality, finite size of source limits the peak amplification (3) Rule of thumb: significant magnification requires an impact parameter smaller than the Einstein ring radius (4) Microlensing is achromatic – all wavelengths affe ...
Measuring the Frequency of Massive Planets around M
... other stars (left). Adaptive optics observations resolve the blended stars and allow a measurement of the lens light (right). ...
... other stars (left). Adaptive optics observations resolve the blended stars and allow a measurement of the lens light (right). ...
Gravitational microlensing
Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers can only detect bright objects that emit much light (stars) or large objects that block background light (clouds of gas and dust). These objects make up only a tiny portion of the mass of a galaxy. Microlensing allows the study of objects that emit little or no light.When a distant star or quasar gets sufficiently aligned with a massive compact foreground object, the bending of light due to its gravitational field, as discussed by Einstein in 1915, leads to two distorted unresolved images resulting in an observable magnification. The time-scale of the transient brightening depends on the mass of the foreground object as well as on the relative proper motion between the background 'source' and the foreground 'lens' object.Since microlensing observations do not rely on radiation received from the lens object, this effect therefore allows astronomers to study massive objects no matter how faint. It is thus an ideal technique to study the galactic population of such faint or dark objects as brown dwarfs, red dwarfs, planets, white dwarfs, neutron stars, black holes, andMassive Compact Halo Objects. Moreover, the microlensing effect is wavelength-independent, allowing study of source objects that emit any kind of electromagnetic radiation.Microlensing by an isolated object was first detected in 1989. Since then, microlensing has been used to constrain the nature of the dark matter, detect extrasolar planets, study limb darkening in distant stars, constrain the binary star population, and constrain the structure of the Milky Way's disk. Microlensing has also been proposed as a means to find dark objects like brown dwarfs and black holes, study starspots, measure stellar rotation, and probe quasars including their accretion disks.