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Diffraction is important when nearby substellar objects gravitationally lens distant stars. If the wavelength of the observation is comparable to the Schwarzschild radius of lensing object, diffraction leaves an observable imprint on the lensing signature. The SKA may have sufficient sensitivity to detect the typical sources, giant stars in the bulge. The diffractive signatures in a lensing event break the degeneracies between the mass of the lens, its distance and proper motion.
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 the high e
Microlensings events are predicted for the light coming from cosmological sources. In addition to the microlensing due to gravitation lensing, microlensing produced also by refraction of light due to either ionized, or not, gas clouds can be consider
The Wide Field Infrared Survey Telescope (WFIRST) will monitor $sim 2$ deg$^2$ toward the Galactic bulge in a wide ($sim 1-2~mu$m) W149 filter at 15-minute cadence with exposure times of $sim$50s for 6 seasons of 72 days each, for a total $sim$41,000
Recent studies suggest the existence of very massive stars (VMS) up to 300 solar masses in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 solar masses, it is timely to evaluate the
We present htof, an open-source tool for interpreting and fitting the intermediate astrometric data (IAD) from both the 1997 and 2007 reductions of Hipparcos, the scanning-law of Gaia, and future missions such as the Nancy Grace Roman Space Telescope