Timing analysis in microlensing

Timing analysis is a powerful tool used to determine periodic features of physical phenomena. Here we review two applications of timing analysis to gravitational microlensing events. The first one, in particular cases, allows the estimation of the orbital period of binary lenses, which in turn enables the breaking of degeneracies. The second one is a method to measure the rotation period of the lensed star by observing signatures due to stellar spots on its surface.Comment: 11 pages, 4 figures. To be published in International Journal of Modern Physics D (IJMPD

Starspot induced effects in microlensing events with rotating source star

We consider the effects induced by the presence of hot and cold spots on the source star in the light curves of simulated microlensing events due to either single or binary lenses taking into account the rotation of the source star and the orbital motion of the lens system. Our goal is to study the anomalies induced by these effects on simulated microlensing light curves.Comment: 5 pages, 2 figures, accepted for publication in MNRA

Search for exoplanets in M31 with pixel-lensing and the PA-99-N2 event revisited

Several exoplanets have been detected towards the Galactic bulge with the microlensing technique. We show that exoplanets in M31 may also be detected with the pixel-lensing method, if telescopes making high cadence observations of an ongoing microlensing event are used. Using a Monte Carlo approach we find that the mean mass for detectable planetary systems is about $2 M_{\rm {J}}$. However, even small mass exoplanets ($M_{\rm P} < 20 M_{\oplus}$) can cause significant deviations, which are observable with large telescopes. We reanalysed the POINT-AGAPE microlensing event PA-99-N2. First, we test the robustness of the binary lens conclusion for this light curve. Second, we show that for such long duration and bright microlensing events, the efficiency for finding planetary-like deviations is strongly enhanced with respect to that evaluated for all planetary detectable events.Comment: 14 pages, 8 figures. Paper presented at the "II Italian-Pakistani Workshop on Relativistic Astrophysics, Pescara, July 8-10, 2009. To be published in a special issue of General Relativity and Gravitation (eds. F. De Paolis, G.F.R. Ellis, A. Qadir and R. Ruffini

Exoplanet Searches in the Habitable Zone with Gravitational Microlensing

There are different methods for finding exoplanets such as radial spectral shifts, astrometrical measurements, transits, timing, etc. Gravitational microlensing (including pixel-lensing) is among the most promising techniques with the potential of detecting Earth-like planets at distances about a few astronomical units from their host stars. Here we emphasize the importance of polarization measurements which can help to resolve degeneracies in theoretical models. In particular, the polarization angle could give additional information about the relative position of the lens with respect to the sourc

Periastron shift in Weyl class spacetimes

The periastron position advance for geodesic motion in axially symmetric solutions of the Einstein field equations belonging to the Weyl class of vacuum solutions is investigated. Explicit examples corresponding to either static solutions (single Chazy-Curzon, Schwarzschild and a pair of them), or stationary solution (single rotating Chazy-Curzon and Kerr black hole) are discussed. The results are then applied to the case of S2-SgrA$^*$ binary system of which the periastron position advance will be soon measured with a great accuracy.Comment: To appear on General Relativity and Gravitation, vol. 37, 200

Hunting for intermediate mass black holes in a sample of close dwarf spheroidal galaxies

We analyse archival XMM-Newton and Chandra observations of some dwarf MW satellites and characterized the X-ray source population by cross-correlating with available databases. We also investigate if intermediate-mass black holes are hosted in the center of these galaxies. In the most interesting case of UMI dwarf, we put an upper limit to the central compact object luminosity of ≃ 4 × 1033 erg s-1. As the target correlates in position also with a radio source, we estimated a black hole mass of ≃ 32.0-2.76+2.54 × 106 M☉

Exoplanet searches in the habitable zone with gravitational microlensing

There are different methods for finding exoplanets such as radial spectral shifts, astrometrical measurements, transits, timing, etc. Gravitational microlensing (including pixel-lensing) is among the most promising techniques with the potential of detecting Earth-like planets at distances about a few astronomical units from their host stars. Here we emphasize the importance of polarization measurements which can help to resolve degeneracies in theoretical models. In particular, the polarization angle could give additional information about the relative position of the lens with respect to the sourc

Efficient Transmission and Characterization of Creutzfeldt–Jakob Disease Strains in Bank Voles

Transmission of prions between species is limited by the “species barrier,” which hampers a full characterization of human prion strains in the mouse model. We report that the efficiency of primary transmission of prions from Creutzfeldt–Jakob disease patients to a wild rodent species, the bank vole (Clethrionomys glareolus), is comparable to that reported in transgenic mice carrying human prion protein, in spite of a low prion protein–sequence homology between man and vole. Voles infected with sporadic and genetic Creutzfeldt–Jakob disease isolates show strain-specific patterns of spongiform degeneration and pathological prion protein–deposition, and accumulate protease-resistant prion protein with biochemical properties similar to the human counterpart. Adaptation of genetic Creutzfeldt–Jakob disease isolates to voles shows little or no evidence of a transmission barrier, in contrast to the striking barriers observed during transmission of mouse, hamster, and sheep prions to voles. Our results imply that in voles there is no clear relationship between the degree of homology of the prion protein of the donor and recipient species and susceptibility, consistent with the view that the prion strain gives a major contribution to the species barrier. The vole is therefore a valuable model to study human prion diversity and, being susceptible to a range of animal prions, represents a unique tool for comparing isolates from different species