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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…

Astrophysics · Physics 2007-05-23 D. Lennon , S. Mao , J. Reetz , T. Gehren , L. Yan , A. Renzini

One possibility for detecting low-amplitude pulsational variations is through gravitational microlensing. During a microlensing event, the temporary brightness increase leads to improvement in the signal-to-noise ratio, and thereby better…

Solar and Stellar Astrophysics · Physics 2021-09-01 Sedighe Sajadian , Richard Ignace , Hilding Neilson

The transition from current Stage-III surveys such as the Kilo-Degree Survey (KiDS) to the increased area and redshift range of Stage IV surveys such as Euclid will significantly increase the precision of weak lensing analyses. However,…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-29 L. Linke , S. Unruh , A. Wittje , T. Schrabback , S. Grandis , M. Asgari , A. Dvornik , H. Hildebrandt , H. Hoekstra , B. Joachimi , R. Reischke , J. L. van den Busch , A. H. Wright , P. Schneider , N. Aghanim , B. Altieri , A. Amara , S. Andreon , N. Auricchio , C. Baccigalupi , M. Baldi , S. Bardelli , D. Bonino , E. Branchini , M. Brescia , J. Brinchmann , S. Camera , V. Capobianco , C. Carbone , V. F. Cardone , J. Carretero , S. Casas , F. J. Castander , M. Castellano , S. Cavuoti , A. Cimatti , G. Congedo , C. J. Conselice , L. Conversi , Y. Copin , F. Courbin , H. M. Courtois , A. Da Silva , H. Degaudenzi , J. Dinis , M. Douspis , F. Dubath , X. Dupac , S. Dusini , M. Farina , S. Farrens , S. Ferriol , P. Fosalba , M. Frailis , E. Franceschi , M. Fumana , S. Galeotta , B. Gillis , C. Giocoli , A. Grazian , F. Grupp , L. Guzzo , S. V. H. Haugan , W. Holmes , I. Hook , F. Hormuth , A. Hornstrup , P. Hudelot , K. Jahnke , E. Keihänen , S. Kermiche , A. Kiessling , M. Kilbinger , T. Kitching , B. Kubik , K. Kuijken , M. Kümmel , M. Kunz , H. Kurki-Suonio , S. Ligori , P. B. Lilje , V. Lindholm , I. Lloro , D. Maino , E. Maiorano , O. Mansutti , O. Marggraf , K. Markovic , N. Martinet , F. Marulli , R. Massey , H. J. McCracken , E. Medinaceli , S. Mei , Y. Mellier , M. Meneghetti , E. Merlin , G. Meylan , M. Moresco , L. Moscardini , E. Munari , R. Nakajima , R. C. Nichol , S. -M. Niemi , J. W. Nightingale , C. Padilla , S. Paltani , F. Pasian , K. Pedersen , V. Pettorino , S. Pires , G. Polenta , M. Poncet , L. A. Popa , F. Raison , R. Rebolo , A. Renzi , J. Rhodes , G. Riccio , E. Romelli , M. Roncarelli , R. Saglia , Z. Sakr , D. Sapone , B. Sartoris , M. Schirmer , A. Secroun , G. Seidel , S. Serrano , C. Sirignano , G. Sirri , L. Stanco , J. -L. Starck , P. Tallada-Crespí , A. N. Taylor , I. Tereno , R. Toledo-Moreo , F. Torradeflot , I. Tutusaus , L. Valenziano , T. Vassallo , G. Verdoes Kleijn , A. Veropalumbo , Y. Wang , J. Weller , G. Zamorani , E. Zucca , C. Burigana , A. Pezzotta , C. Porciani , V. Scottez , M. Viel , A. M. C. Le Brun

To improve photometric precision by removing blending effect, a newly developed technique of difference image analysis (DIA) is adopted by several gravitational microlensing experiment groups. However, the principal problem of the DIA…

Astrophysics · Physics 2009-10-31 Cheongho Han

We compute the predicted optical depth and duration distribution of microlensing events towards Baade's window in a model composed of a Galactic disk and a bar. The bar model is a self-consistent dynamical model built out of individual…

Astrophysics · Physics 2009-10-22 HongSheng Zhao , David N. Spergel , R. Michael Rich

We show that the statistical error, $\sigma_{\tau}$, in estimating the optical depth, $\tau$, due to microlensing is substantially higher than the naive Poisson estimate: $\sigma_{\tau} = \sqrt{\eta / N} \tau$, where $N$ is the number of…

Astrophysics · Physics 2009-10-22 Cheongho Han , Andrew Gould

We present the analysis of the binary-lens microlensing event OGLE-2017-BLG-0537. The light curve of the event exhibits two strong caustic-crossing spikes among which the second caustic crossing was resolved by high-cadence surveys. It is…

We estimate the rate of near-field microlensing events expected from all-sky surveys and investigate the properties of these events. Under the assumption that all lenses are composed of stars, our estimation of the event rate ranges from…

Astrophysics · Physics 2009-11-13 Cheongho Han

To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that central…

Microlensing searches toward the inner galaxy $(|l|,|b|\leq 22.\hskip-2pt'5)$ have several major advantages. First, the event rate is strongly dominated by bulge-bulge lensing events where both the source and lens lie in the bulge. Second,…

Astrophysics · Physics 2009-10-22 Andrew Gould

The current weak lensing measurements of the large scale structure are mostly related to statistical study of background galaxy ellipticities. We consider a possibility to extend lensing studies with intrinsically unresolved sources and…

Astrophysics · Physics 2008-11-26 Asantha Cooray

The computation of the magnification of a finite source by an arbitrary gravitational lens can be reduced from a two-dimensional to a one-dimensional integral using a generalization of Stoke's theorem. For a large source lensed by a…

Astrophysics · Physics 2007-05-23 Andrew Gould , Cedric Gaucherel

We present the photometry and theoretical models for a Galactic bulge microlensing event OGLE-2000-BUL-43. The event is very bright with I=13.54 mag, and has a very long time scale, t_E=156 days. The long time scale and its light curve…

We analyze the lightcurve of the microlensing event OGLE-2003-BLG-175/MOA-2003-BLG-45 and show that it has two properties that, when combined with future high resolution astrometry, could lead to a direct, accurate measurement of the lens…

Astrophysics · Physics 2009-11-10 H. Ghosh

This study commenced by cross-matching data from the GAIA and OGLE telescopes with the aim of resolving the source star, long after microlensing is finished. The aim is breaking degeneracy between parameters of the microlensing equation,…

Instrumentation and Methods for Astrophysics · Physics 2024-05-28 Saeed Mozaheb , Sohrab Rahvar

The microlensing probability (optical depth $\tau$) toward the Galactic center carries information about the mass distribution of the Galactic bulge/bar, so can be used to constrain the very uncertain shape parameters of the bar. We find…

Astrophysics · Physics 2015-06-24 HongSheng Zhao , Shude Mao

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…

We present the open-source Python package, BAGLE (Bayesian Analysis of Gravitational Lensing Events), which enables modeling and joint fitting of photometric and astrometric data sets. We describe the model parameterizations and present the…

Solar and Stellar Astrophysics · Physics 2025-12-04 J. R. Lu , M. Medford , C. Y. Lam , T. D. Bhadra , M. J. Huston , N. S. Abrams , E. Broadberry , J. Chen , S. K. Terry , N. Arredondo , A. Scharf

The MACHO collaboration has recently analyzed 2.1 years of photometric data for about 8.5 million stars in the Large Magellanic Cloud (LMC). This analysis has revealed 8 candidate microlensing events and a total microlensing optical depth…

Chromaticity effects introduced by the finite source size in microlensing events by presumed natural wormholes are studied. It is shown that these effects provide a specific signature that allow to discriminate between ordinary and negative…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Ernesto Eiroa , Gustavo E. Romero , Diego F. Torres