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We have been spectroscopically monitoring 88 quasars selected to have broad H$\beta$ emission lines offset from their systemic redshift by thousands of km s$^{-1}$. By analogy with single-lined spectroscopic binary stars, we consider these…

With about a hundred mergers of binary black holes (BBHs) detected via gravitational waves by the LIGO-Virgo-KAGRA (LVK) Collaboration, our understanding of the darkest objects in the Universe has taken unparalleled steps forward. While…

Astrophysics of Galaxies · Physics 2023-07-19 Giacomo Fragione , Frederic A. Rasio

We examine the distribution of masses of black holes in transient low mass X-ray binary systems. A Bayesian analysis suggests that it is probable that six of the seven systems with measured mass functions have black hole masses clustered…

Astrophysics · Physics 2009-10-30 Charles D. Bailyn , Raj K. Jain , Paolo Coppi , Jerome A. Orosz

Recent work on the modes of accretion onto black holes (BHs) in Soft X-Ray Transients (SXTs) is reviewed, with an emphasis on uncertainties affecting models of accretion during quiescence (inner hot flow, outer thin disk). Various…

Astrophysics · Physics 2017-08-23 Kristen Menou

Recent work has linked the quiescent luminosities and hard/soft spectral state switches of neutron stars (NSs) to their spinning magnetic fields. It is shown here that the quiescent luminosities and spectral switches of galactic black hole…

Astrophysics · Physics 2007-05-23 Stanley L. Robertson

Studies of nearby galaxies reveal that roughly half of their low mass X-ray binary (LMXB) populations are associated with globular clusters (GCs). We have established that the LMXB hosting frequency is correlated to various GC properties…

With references to both key and oft-forgotten pioneering works, this article starts by presenting a review into how we came to believe in the existence of massive black holes at the centres of galaxies. It then presents the historical…

Astrophysics of Galaxies · Physics 2016-09-07 Alister W. Graham

We have searched for long duration microlensing events originating from intermediate mass Black Holes (BH) in the halo of the Milky Way, using archival data from EROS-2 and MACHO photometric surveys towards the Large Magellanic Cloud. We…

The dynamics of apparent and event horizons of various black hole spacetimes, including those containing distorted, rotating and colliding black holes, are studied. We have developed a powerful and efficient new method for locating the…

General Relativity and Quantum Cosmology · Physics 2009-10-22 Peter Anninos , David Bernstein , Steven Brandt , Joseph Libson , Joan Masso , Edward Seidel , Larry Smarr , Wai-Mo Suen , Paul Walker

Isolated black holes and neutron stars can be revealed through the observation of long duration gravitational microlensing events. A few candidates have been found in surveys of stars in the direction of the Galactic bulge. Recently, thanks…

High Energy Astrophysical Phenomena · Physics 2022-08-03 Sandro Mereghetti , Lara Sidoli , Gabriele Ponti , Aldo Treves

The dark and dynamic parts of the Galaxy, including the bulk shape and movement of the Galactic Bulge and characteristics of dark compact object populations, such as a hypothetical population of primordial black holes (PBHs), are difficult…

Astrophysics of Galaxies · Physics 2025-03-31 Scott E. Perkins , Peter McGill , William A. Dawson , Ming-Feng Ho , Natasha S. Abrams , Simeon Bird , Jessica R. Lu

The case for collapsed objects in some X-ray binary systems continues to strengthen. But there is now even firmer evidence for supermassive black holes in galactic centres. Gravitational collapse seems to have occurred in the centres of…

Astrophysics · Physics 2008-02-03 Martin J. Rees

The majority of known Galactic black holes reside in low-mass X-ray binaries. They are rare and fascinating objects, providing unique information on strong gravity, accretion disc physics, and stellar and binary evolution. There is no doubt…

High Energy Astrophysical Phenomena · Physics 2015-06-24 Xiang-Dong Li

It has been shown by Paczy\'nski that gravitational microlensing is potentially a useful method for detecting the dark constituents of the halo of our galaxy, if their mass lies in the approximate domain $10^{-6} < M/M_{\odot} < 10^{-1}$.…

Astrophysics · Physics 2008-02-03 Philippe Jetzer

Mass distribution of black holes in low-mass X-ray binaries previously suggested the existence of a $ \sim 2-5M_{\odot} $ mass gap between the most massive neutron stars and the least massive black holes, while some recent evidence appears…

High Energy Astrophysical Phenomena · Physics 2022-11-30 Yong Shao

Sizeable number of stellar-mass black holes (BHs) in globular clusters (GCs) can strongly influence the dynamical evolution and observational properties of their host cluster. Using results from a large set of numerical simulations, we…

Astrophysics of Galaxies · Physics 2020-03-18 Abbas Askar , Mirek Giersz , Manuel Arca Sedda , Ammar Askar , Mario Pasquato , Agostino Leveque

The Mock LISA Data Challenges are a programme to demonstrate and encourage the development of LISA data-analysis capabilities, tools and techniques. At the time of this workshop, three rounds of challenges had been completed, and the next…

We show that at any given time, the Galactocentric black hole Sgr A* is expected to be microlensing N(lens)=1.7 bulge stars if the threshold of detectability of the fainter image is K(thr)=21, and about N(lens)=8 sources if K(thr)=23. The…

Astrophysics · Physics 2009-11-06 Julio Chaname , Andrew Gould , Jordi Miralda-Escude

Stellar-mass black holes ($3$ $M_\odot \lesssim M_{\rm BH} \lesssim 150$ $M_\odot$) are the natural product of the evolution of heavy stars ($M_{\rm star} \gtrsim 20$ $M_\odot$). In our Galaxy, we expect $10^8$-$10^9$ stellar-mass black…

High Energy Astrophysical Phenomena · Physics 2025-08-27 Cosimo Bambi

Upcoming VLBI observations will resolve nearby supermassive black holes, most notably Sagittarius A* and M87, on event horizon-scales. Recent observations of Sagittarius A* with the Event Horizon Telescope have revealed horizon-scale…

High Energy Astrophysical Phenomena · Physics 2020-04-15 Ziri Younsi , Oliver Porth , Yosuke Mizuno , Christian M. Fromm , Hector Olivares