Related papers: Response to Comment on "A Non-Interacting Low-Mass…
We analyse the apparent disagreement between the mass estimates of the central black hole(s) in Mkn~501 based on (i) the observations of the host galaxy, (ii) the high energy (HE) emission mechanism, and (iii) the modulation of the beamed…
We report the discovery and analysis of a massive, compact, hierarchical triple system (TIC 470710327) initially identified by citizen scientists in data obtained by NASA's Transiting Exoplanet Survey Satellite (TESS). Spectroscopic…
We show that the radial velocity-variable star in the black hole candidate NGC 1850 BH1 cannot be a normal $\approx 5\,M_{\odot}$ subgiant, as was proposed, but is an overluminous stripped-envelope star with mass $\approx 1 M_{\odot}$. The…
We analyze the dynamical evolution of binary stars that interact with a static background of single stars in the environment of a massive black hole (MBH). All stars are considered to be single mass, Newtonian point particles. We follow the…
The determination of unseen companion masses ($M_1$) is essential for identifying compact objects in binary systems, yet obtaining reliable orbital inclinations remains one of the most difficult challenges. In this study, we focus on ten…
We report the discovery of a quasar close to SDSS J0927+2943 (z = 0.713), which is a massive binary / recoiling black hole candidate. The companion quasar is at a projected distance of 125 h_70^{-1} kpc and exhibits a radial velocity…
We predict the number of black holes with stellar companions that are potentially detectable with Gaia astrometry over the course of its five-year mission. Our model estimates that nearly 2$\times$10$^5$ astrometric binaries hosting black…
Among the four black hole binary merger events detected by LIGO, six progenitor black holes have masses greater than 20\,$M_\odot$. The existence of such massive BHs calls for extreme metal-poor stars as the progenitors. An alternative…
Recent observational results provide possible evidence that binary black holes (BBHs) exist in the center of giant galaxies and may merge to form a supermassive black hole in the process of their evolution. We first detected a periodic flux…
We present a new constraint on the mass of the black hole in the active S0 galaxy NGC 5273. Due to the proximity of the galaxy at $16.6 \pm 2.1$ Mpc, we were able to resolve and extract the bulk motions of stars near the central black hole…
The formation and evolution of binary black holes (BH) is studied using the modern evolutionary scenario for very massive stars with high mass loss (Vanbeveren et al. 1998). Main sequence stars with masses $M>35 M_\odot$ are assumed to form…
It is now well established that a large fraction of the low-mass stars are binaries or higher order multiples. Similarly a sizable fraction have giant planets. In contrast to these, the situation for brown dwarf companions is complicated:…
The LIGO/Virgo collaboration has recently announced the detection of a heavy binary black hole merger, with component masses that cannot be explained by standard stellar structure theory. In this letter we propose several explanations based…
In the present-day universe, supermassive black hole masses (MBH) appear to be strongly correlated with their galaxy's bulge luminosity, among other properties. In this study, we explore the analogous relationship between MBH, derived using…
New spectroscopic observations of the LBV/WR multiple system HD5980 in the Small Magellanic Cloud are used to address the question of the masses and evolutionary status of the two very luminous stars in the 19.3d eclipsing binary system.…
A discussion of the entropy of the universe leads to the suggestion of very many intermediate-mass black holes between thirty and three hundred thousand solar masses in the halo. It is consistent with observations on wide binaries as well…
We use the clustering of galaxies around distant active-galactic nuclei to derive an estimate of the relationship between galaxy and black hole mass that obtained during the ancient quasar epoch, at redshifts 2 <~ z <~ 3, when giant black…
Quasars at early redshifts ($z > 6$) with companion galaxies offer unique insights into the growth and evolution of the first supermassive black holes. Here, we report on a 150 ks Chandra observation of PSO J308.0416$-$21.2339, a $z=6.23$…
In binary black-hole mergers from isolated binary-star evolution, both black holes are from progenitor stars that have lost their hydrogen-rich envelopes by binary mass transfer. Envelope stripping is known to affect the pre-supernova core…
While there are a number of proposed formation channels for subsolar mass compact objects, including black holes formed primordially, or neutron stars that form in collapsar disks, there have yet to be any conclusive observations of such…