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Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by…

The analysis of the first two years of OGLE data revealed 9 microlensing events of the galactic bulge stars, with the characteristic time scales in the range $ 8.6 < t_0 < 62 $ days, where $ t_0 = R_E / V $. The optical depth to…

天体物理学 · 物理学 2008-12-18 B. Paczynski , K. Z. Stanek , A. Udalski , M. Szymanski , J. Kaluzny , M. Kubiak , M. Mateo , W. Krzeminski

The gravitational microlensing as a unique astrophysical tool can be used for studying the atmosphere of stars thousands of parsec far from us. This capability results from the bending of light rays in the gravitational field of a lens…

太阳与恒星天体物理 · 物理学 2015-08-06 Sedighe Sajadian , Sohrab Rahvar

We present the result of microlensing event MOA-2016-BLG-290, which received observations from the two-wheel Kepler (K2), Spitzer, as well as ground-based observatories. A joint analysis of data from K2 and the ground leads to two…

The availability of photometric imaging of several thousand galaxies with the Spitzer Space Telescope enables a mid-infrared calibration of the correlation between luminosity and rotation in spiral galaxies. The most important advantage of…

宇宙学与河外天体物理 · 物理学 2015-06-11 Jenny G. Sorce , Helene M. Courtois , R. Brent Tully

The microlens parallax is a crucial observable for conclusively identifying the nature of lens systems in microlensing events containing or composed of faint (even dark) astronomical objects such as planets, neutron stars, brown dwarfs, and…

We report the detection of 45 candidate microlensing events in fields toward the Galactic bulge. These come from the analysis of 24 fields containing 12.6 million stars observed for 190 days in 1993. Many of these events are of extremely…

The MACHO Project is a search for dark matter in the form of massive compact halo objects (Machos). Photometric monitoring of millions of stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and Galactic bulge is used to…

Gravitational microlensing is a powerful method for discovering Isolated Stellar-Mass Black Holes(ISMBHs). These objects make long-duration microlensing events. To characterize these lensing objects by fully resolving the microlensing…

星系天体物理 · 物理学 2023-09-15 Sedighe Sajadian , Arya Mahmoudzadeh , Setareh Moein

Foundations of standard theory of microlensing are described, namely we consider microlensing stars in Galactic bulge, the Magellanic Clouds or other nearby galaxies. We suppose that gravitational microlenses lie between an Earth observer…

天体物理学 · 物理学 2007-05-23 A. F. Zakharov

Three ongoing microlensing experiments have found more candidate events than expected from the known stars. These experiments measure only one parameter of the massive compact halo objects (machos), the magnification time scale of the…

天体物理学 · 物理学 2009-10-28 Thomas Boutreux , Andrew Gould

The primary goal of this paper is to provide the evidence that can either prove or falsify the hypothesis that dark matter in the Galactic halo can clump into stellar-mass compact objects. If such objects existed, they would act as lenses…

Spitzer microlensing parallax observations of OGLE-2015-BLG-1212 decisively breaks a degeneracy between planetary and binary solutions that is somewhat ambiguous when only ground-based data are considered. Only eight viable models survive…

A high optical depth to gravitational microlensing towards the galactic bulge is consistent with current models of the galactic bar. The low optical depth towards the LMC can probably be accounted for by the ordinary stars in our galaxy and…

天体物理学 · 物理学 2016-08-30 Bohdan Paczynski

Parallax is the most fundamental technique to measure distances to astronomical objects. Although terrestrial parallax was pioneered over 2000 years ago by Hipparchus (ca. 140 BCE) to measure the distance to the Moon, the baseline of the…

星系天体物理 · 物理学 2011-02-11 A. Gould , A. Udalski , B. Monard , K. Horne , Subo Dong , N. Miyake , K. Sahu , D. P. Bennett , the OGLE , MicroFUN , RoboNet , MOA , PLANET collaborations

We propose a near-infrared microlensing survey of the central 2 degree field of the Galactic Center, in an attempt to estimate the surface density and mass distribution of distant free-floating brown dwarfs in the bulge and in the disk,…

天体物理学 · 物理学 2016-08-30 Hans Zinnecker

We describe a real-time spectroscopic program to observe bright gravitational microlensing events toward the Galactic Bulge. The program is carried out using the NTT at ESO. We present the preliminary analysis of the microlensing events we…

天体物理学 · 物理学 2007-05-23 D. Lennon , S. Mao , J. Reetz , T. Gehren , L. Yan , A. Renzini

We have obtained mid-infrared spectra of nine cool-core galaxy clusters with the Infrared Spectrograph aboard the Spitzer Space Telescope. X-ray, ultraviolet and optical observations have demonstrated that each of these clusters hosts a…

宇宙学与河外天体物理 · 物理学 2009-08-25 G. E. de Messières , R. W. O'Connell , B. R. McNamara , M. Donahue , P. E. J. Nulsen , G. M. Voit , M. W. Wise

Microlensing is the only known direct method to measure the masses of stars that lack visible companions. In terms of microlensing observables, the mass is given by M=(c^2/4G)\tilde r_E \theta_E and so requires the measurement of both the…

Due to dramatic improvements in the precision of astrometric measurements, the observation of light centroid shifts in observed stars due to intervening massive compact objects (`astrometric microlensing') will become possible in the near…

天体物理学 · 物理学 2007-05-23 Martin Dominik , Kailash C. Sahu