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The nature and the location of the lenses discovered in the microlensing surveys done so far towards the LMC remain unclear. Motivated by these questions we computed the optical depth for the different intervening populations and the number…

Astrophysics · Physics 2007-05-23 Philippe Jetzer

During the months when the galactic bulge is visible from the southern hemisphere, there are typically about 8 to 10 on-going microlensing events at any given time. If the lensing stars have planets around them, then the signature of the…

Astrophysics · Physics 2007-05-23 Kailash C. Sahu

If compact baryonic objects contribute significantly to the dark matter in our Galaxy, their mass function will present vital clues for galaxy formation theories and star formation processes in the early Universe. Here we discuss what one…

Astrophysics · Physics 2008-11-26 E. J. Kerins , B. J. Carr

We combine the available astrometric and photometric data for the 1993 microlensing event MACHO-LMC-5 to measure the mass of the lens, M=0.097 +/- 0.016 Msun. This is the most precise direct mass measurement of a single star other than the…

Astrophysics · Physics 2009-11-10 Andrew Gould , David P. Bennett , David R. Alves

Traditional approaches to measuring the stellar mass function (MF) are fundamentally limited because objects are detected based on their luminosity, not their mass. These methods are thereby restricted to luminous and relatively nearby…

Astrophysics · Physics 2009-10-28 Andrew Gould

A significant fraction of non-baryonic or baryonic dark matter in galactic halos may consist of MASsive Compact Objects (MASCOs) with mass M=10^{1-4}M_{sun}. Possible candidates for such compact objects include primordial black holes or…

Astrophysics · Physics 2009-11-07 Kaiki Taro Inoue , Masashi Chiba

Estimating the number of microlensing events observed in different parts of the Galactic bulge is a crucial point in planning microlensing experiments. Reliable estimates are especially important if observing resources are scarce, as is the…

Astrophysics of Galaxies · Physics 2015-12-09 R. Poleski

The EROS microlensing survey has monitored nearly 100 million stars for seven years, to search for halo brown dwarfs and compact objects in the Galactic disk. In this paper, we review the various EROS observation programs and the…

Astrophysics · Physics 2007-05-23 R. Ansari

Caustic crossing microlensing events provide us a unique opportunity to measure the relative proper motion of the lens to the source, and so those caused by binary MACHOs are of great importance for understanding the structure of the…

Astrophysics · Physics 2009-10-31 Mareki Honma

We present microlens parallax measurements for 21 (apparently) isolated lenses observed toward the Galactic bulge that were imaged simultaneously from Earth and Spitzer, which was ~1 AU West of Earth in projection. We combine these…

We present the Catalog of microlensing events detected toward the Galactic bulge in three observing seasons, 1997--1999, during the OGLE-II microlensing survey. The search for microlensing events was performed using a database of about…

Astrophysics · Physics 2007-05-23 A. Udalski , K. Zebrun , M. Szymanski , M. Kubiak , G. Pietrzynski , I. Soszynski , P. Wozniak

The EROS-2 project was designed to test the hypothesis that massive compact halo objects (the so-called ``machos'') could be a major component of the dark matter halo of the Milky Way galaxy. To this end, EROS-2 monitored over 6.7 years…

Microlensing has a unique advantage for detecting dark objects in the Milky Way, such as free-floating planets, neutron stars, and stellar-mass black holes. Most microlensing surveys focus on the Galactic bulge, where higher stellar density…

Astrophysics of Galaxies · Physics 2024-11-11 Ruocheng Zhai , Antonio C. Rodriguez , Shude Mao , Casey Y. Lam , Eric C. Bellm , Josiah Purdum , Frank J. Masci , Avery Wold

We propose the existence of ultracompact minihalos as a new type of massive compact halo object (MACHO) and suggest an observational test to discover them. These new MACHOs are a powerful probe into the nature of dark matter and physics in…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 M. Ricotti , A. Gould

The longest microlensing events provide enough information to estimate the mass and distance of the lens. Among hundreds of millions of stars which were monitored for many years by the OGLE project we selected those with clear parallax…

Solar and Stellar Astrophysics · Physics 2016-01-13 Łukasz Wyrzykowski , Zuzanna Kostrzewa-Rutkowska , Krzysztof Rybicki

We report the final analysis of a search for microlensing events in the direction of the Andromeda galaxy, which aimed to probe the MACHO composition of the M31 halo using data collected during the 1998-99 observational campaign at the MDM…

Gould & DePoy proposed a pixel lensing survey towards the Galactic bulge using a small aperture (~65 mm) camera with a large pixel size (10") detector and deliberately degraded optics achieving 30" PSF. In this paper, we estimate the event…

Astrophysics · Physics 2009-11-06 Cheongho Han

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

Massive Compact objects in the halo, known as MACHOs, have been postulated as the origin of a substantial fraction of `dark matter' known to exist in the haloes of galaxies$^{1,2}$. Paczy\'nski$^3$ has suggested that it might possible to…

Astrophysics · Physics 2015-06-24 Kailash C. Sahu

I show that by observing microlensing events both astrometrically and photometrically, the Space Interferometry Mission (SIM) can measure the mass function of stellar remnants in the Galactic bulge including white dwarfs, neutron stars, and…

Astrophysics · Physics 2009-10-31 Andrew Gould