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Calchi Novati S.,Istituto Internazionale per gli Alti Studi Scientifici | Calchi Novati S.,University of Zurich | Calchi Novati S.,University of Salerno | Mirzoyan S.,University of Zurich | And 5 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present a new analysis of the results of the Expérience pour la Recherche d'Objets Sombres (EROS)-2, Optical Gravitational Lensing Experiment (OGLE)-II and OGLE-III microlensing campaigns towards the Small Magellanic Clouds (SMC). Through a statistical analysis we address the issue of the nature of the reported microlensing candidate events, whether to be attributed to lenses belonging to known population [the SMC luminous components or the MilkyWay disc, to which we broadly refer to as 'self-lensing'] or to the would be population of dark matter compact halo objects (MACHOs). To this purpose, we present profiles of the optical depth and, comparing to the observed quantities, we carry out analyses of the events position and duration. Finally, we evaluate and study the microlensing rate. Overall, we consider five reported microlensing events towards the SMC(one byEROSand four by OGLE). The analysis shows that in terms of number of events the expected self-lensing signal may indeed explain the observed rate. However, the characteristics of the events, spatial distribution and duration (and for one event, the projected velocity) rather suggest a non-self-lensing origin for a few of them. In particular, we evaluate, through a likelihood analysis, the resulting upper limit for the halo mass fraction in form of MACHOs given the expected self-lensing and MACHO lensing signal. At 95 per cent CL, the tighter upper limit, about 10 per cent, is found forMACHO mass of 10-2M⊙, upper limit that reduces to above 20 per cent for 0.5M⊙ MACHOs. © 2013 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society. Source


Rossini N.,Istituto Internazionale per gli Alti Studi Scientifici
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Deception is a determinant social phenomenon already observed extensively in the literature of several different research fields. This study presents the analysis of both micro-expressions and voice features in sample TV clips, in order to outline a defined research agenda on the topic. © 2011 Springer-Verlag. Source


Choi J.-Y.,Chungbuk National University | Han C.,Chungbuk National University | Udalski A.,University of Warsaw | Sumi T.,Osaka University | And 135 more authors.
Astrophysical Journal | Year: 2013

Although many models have been proposed, the physical mechanisms responsible for the formation of low-mass brown dwarfs (BDs) are poorly understood. The multiplicity properties and minimum mass of the BD mass function provide critical empirical diagnostics of these mechanisms. We present the discovery via gravitational microlensing of two very low mass, very tight binary systems. These binaries have directly and precisely measured total system masses of 0.025 M· and 0.034 M·, and projected separations of 0.31 AU and 0.19 AU, making them the lowest-mass and tightest field BD binaries known. The discovery of a population of such binaries indicates that BD binaries can robustly form at least down to masses of 0.02 M·. Future microlensing surveys will measure a mass-selected sample of BD binary systems, which can then be directly compared to similar samples of stellar binaries. © 2013. The American Astronomical Society. All rights reserved. Source


Skottfelt J.,Copenhagen University | Bramich D.M.,European Southern Observatory | Figuera Jaimes R.,European Southern Observatory | Figuera Jaimes R.,University of St. Andrews | And 38 more authors.
Astronomy and Astrophysics | Year: 2013

Two previously unknown variable stars in the crowded central region of the globular cluster NGC 6981 are presented. The observations were made using the electron multiplying CCD (EMCCD) camera at the Danish 1.54 m Telescope at La Silla, Chile. The two variableswere not previously detected by conventional CCD imaging because of their proximity to a bright star. This discovery demonstrates that EMCCDs are a powerful tool for performing high-precision time-series photometry in crowded fields and near bright stars, especially when combined with difference image analysis. © ESO, 2013. Source


Calchi Novati S.,Istituto Internazionale per gli Alti Studi Scientifici | Calchi Novati S.,University of Salerno | Bozza V.,University of Salerno | Bozza V.,National Institute of Nuclear Physics, Italy | And 23 more authors.
Astrophysical Journal | Year: 2014

We present the final analysis of the observational campaign carried out by the PLAN (Pixel Lensing Andromeda) collaboration to detect a dark matter signal in form of MACHOs through the microlensing effect. The campaign consists of about 1 month/year observations carried out over 4 years (2007-2010) at the 1.5 m Cassini telescope in Loiano (Astronomical Observatory of BOLOGNA, OAB) plus 10 days of data taken in 2010 at the 2 m Himalayan Chandra Telescope monitoring the central part of M31 (two fields of about 13′ × 12.′6). We establish a fully automated pipeline for the search and the characterization of microlensing flux variations. As a result, we detect three microlensing candidates. We evaluate the expected signal through a full Monte Carlo simulation of the experiment completed by an analysis of the detection efficiency of our pipeline. We consider both "self lensing" and "MACHO lensing" lens populations, given by M31 stars and dark matter halo MACHOs, in M31 and the Milky Way, respectively. The total number of events is consistent with the expected self-lensing rate. Specifically, we evaluate an expected signal of about two self-lensing events. As for MACHO lensing, for full 0.5(10-2) M⊙ MACHO halos, our prediction is for about four (seven) events. The comparatively small number of expected MACHO versus self-lensing events, together with the small number statistics at our disposal, do not enable us to put strong constraints on that population. Rather, the hypothesis, suggested by a previous analysis, on the MACHO nature of OAB-07-N2, one of the microlensing candidates, translates into a sizeable lower limit for the halo mass fraction in form of the would-be MACHO population, f, of about 15% for 0.5 M⊙ MACHOs. © 2014. The American Astronomical Society. All rights reserved. Source

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