Related papers: Eppur non si trovano: Comments on the Primordial B…
The nature of the dark matter in the halo of our Galaxy is still largely unknown. The microlensing events found so far towards the Large Magellanic Cloud suggest that at most about 20% of the halo dark matter is in the form of MACHOs…
We consider the possibility that the black-hole (BH) binary detected by LIGO may be a signature of dark matter. Interestingly enough, there remains a window for masses $20\,M_\odot \lesssim M_{\rm bh} \lesssim 100\, M_\odot$ where…
Gravitational microlensing is one of the few means of finding primordial black holes (PBHs), if they exist. Recent LIGO detections of 30 Msun black holes have re-invigorated the search for PBHs in the 10-100 Msun mass regime. Unfortunately,…
Primordial black holes (PBHs) have long been suggested as a candidate for making up some or all of the dark matter in the Universe. Most of the theoretically possible mass range for PBH dark matter has been ruled out with various null…
Though stellar-mass black holes (BHs) are likely abundant in the Milky Way (N=10^8-10^9), only ~20 have been detected to date, all in accreting binary systems (Casares 2006). Gravitational microlensing is a proposed technique to search for…
The recent astrometric data of hundreds of millions of stars from Gaia DR3 has allowed a precise determination of the Milky Way rotation curve up to $28$~kpc. The data suggests a rapid decline in the density of dark matter beyond $19$~kpc.…
The motivation for this paper is to review the limits set on the MACHO content of the Galactic halo by microlensing experiments in the direction of the Large Magellanic Cloud. This has been prompted by recent measurements of the Galactic…
The abundance of primordial black holes is currently significantly constrained in a wide range of masses. The weakest limits are established for the small mass objects, where the small intensity of the associated physical phenomenon…
Recent observations of microlensing events in the Large Magellanic Cloud by the MACHO and EROS collaborations suggest that an important fraction of the galactic halo is in the form of Massive Halo Objects (MHO) with mass $\sim 0.1…
We discuss the implications of the more than 50 microlensing events seen by the EROS, MACHO, and OGLE collaborations for the composition of the halo of our galaxy. The event rates indicate that the halo mass fraction in MACHO's is less than…
We report the detection of a 282 $^{+34}_{-31}$ pc-sized core in the center of Milky Way dark matter halo at $68\%$ confidence level by using the micro-lensing event rate sky map data from the Optical Gravitational Lensing Experiment (OGLE)…
We suggest a new component of the Milky Way galaxy that can account for both the optical depth and the event durations obtained by the MACHO microlensing survey toward the Large Magellanic Cloud. This component is consistent with recent…
In the mass range of 1e15 g up to 1e26 g, primordial black holes (PBHs) as a possible contribution to the dark matter are still unexplored. In this contribution, we investigate the possibility of an electromagnetic signal from PBH…
We update the constraints on the fraction of the Universe that may have gone into primordial black holes (PBHs) over the mass range $10^{-5}\text{--}10^{50}$ g. Those smaller than $\sim 10^{15}$ g would have evaporated by now due to Hawking…
Microlensing has established itself as a powerful new method for the detection of baryonic dark matter in the Galaxy. The theory of microlensing is sketched and its similarity with the optical effect of twinkling is explained. The bulk of…
If massive black holes constitute the dark matter in the halo surrounding the Milky Way, the existence of low mass globular clusters in the halo suggests an upper limit to their mass, $M_{_{BH}}$. We use a combination of the impulse…
The existence of compact gravitational lenses, with masses around 0.5 (M_{\odot}), has been reported in the halo of the Milky Way. The nature of these dark lenses is as yet obscure, particularly because these objects have masses well above…
We present the basics of microlensing and give an overview of the results obtained so far. We also describe a scenario in which dark clusters of MACHOs (Massive Astrophysical Compact Halo Objects) and cold molecular clouds (mainly of $H_2$)…
Primordial Black Holes (PBHs) with a mass $M \lesssim {10^{17}}$g are expected to inject sub-GeV electrons and positrons in the Galaxy via Hawking radiation. These cosmic rays are shielded by the solar magnetic field for Earth-bound…
Intermediate Mass Black Holes (IMBHs) are a class of black holes with masses in the range $10^2 \div 10^5$ $M_\odot$, which can not directly derive from stellar evolution. Looking for these objects and estimating their abundance is…