Related papers: On minor black holes in galactic nuclei
We review the recent multifrequency studies of galactic black hole binaries, aiming at revealing the underlying emission processes and physical properties in these systems. The optical and infrared observations are important for determining…
Ultra-luminous X-ray sources (ULXs) are off-nuclear X-ray sources in nearby galaxies with X-ray luminosities $\geq$ 10$^{39}$ erg s$^{-1}$. The measurement of the black hole (BH) masses of ULXs is a long-standing problem. Here we estimate…
Ultraluminous infrared galaxies (ULIRGs) with multiple ($\ge 3$) nuclei are frequently observed. It has been suggested that these nuclei are produced by multiple major mergers of galaxies. The expected rate of such mergers is, however, too…
The centers of elliptical galaxies host supermassive black holes that significantly affect the surrounding interstellar medium through feedback resulting from the accretion process. The evolution of this gas and of the nuclear emission…
Using the black hole merger rate inferred from LIGO, we calculate the abundance of tightly bound binary black holes in the Milky Way galaxy. Binaries with a small semimajor axis ($\lesssim 10 R_\odot$) originate at larger separations…
We review observations of ultraluminous X-ray sources (ULXs). X-ray spectroscopic and timing studies of ULXs suggest a new accretion state distinct from those seen in Galactic stellar-mass black hole binaries. The detection of coherent…
Massive central objects affect both the structure and evolution of galactic nuclei. Adiabatic growth of black holes generates power-law central density profiles with logarithmic slopes in the range from ~1.5 to ~2.5, in good agreement with…
Accretion states, which are universally observed in stellar-mass black holes in X-ray binaries, are also anticipated in active galactic nuclei (AGN). This is the case at low luminosities, when the jet-corona coupling dominates the energy…
Low-luminosity AGN (with X-ray luminosity < 1e42 ergs/s) far outnumber ordinary AGN, and are therefore perhaps more relevant to our understanding of AGN phenomena and the relationship between AGN and host galaxies. Many normal galaxies…
Supermassive black holes (SMBH) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGN) produce a characteristic transit lightcurve, just like extrasolar…
While until recently they were often considered as exotic objects of dubious existence, in the last decades there have been overwhelming observational evidences for the presence of stellar mass black holes in binary systems, supermassive…
Galaxy mergers provide a mechanism for galaxies to effectively funnel gas and materials toward their nuclei and fuel the central starbursts and accretion of supermassive black holes. In turn, the active nuclei drive galactic-scale outflows…
Many theories for the formation of massive black holes in galactic nuclei predict that the stellar motions should be anisotropic within the radius of influence of the black hole. We report tentative evidence for such an effect in M87.
Cool thermal emission components have recently been revealed in the X-ray spectra of a small number of ultra-luminous X-ray (ULX) sources with L_X > 1 E+40 erg/s in nearby galaxies. These components can be well fitted with accretion disk…
Massive black holes are key inhabitants of the nuclei of galaxies. Moreover, their astrophysical relevance has gained significant traction in recent years, thanks especially to the amazing results that are being (or will be) delivered by…
The low-mass end of the supermassive black hole mass function is unknown and difficult to determine. Here we discuss our successful program to find active nuclei of late type "normal" galaxies using X-ray detections and multiwavelength…
If very low mass primordial black holes (PBH) within the asteroid/moon-mass range indeed reside in galactic dark matter halos, they must necessarily collide with galactic neutron stars (NSs). These collisions must, again necessarily, form…
Accreting black holes are unique tools to understand the physics under extreme gravity. While black hole X-ray binaries differ vastly in mass from AGN, their accretion and ejection flows are assumed to be essentially similar. Black hole…
We propose a simple and unambiguous way to deduce the parameters of black holes which may reside in AGNs and some types of X-ray binaries. The black-hole mass and angular momentum are determined in physical units. The method is applicable…
Black hole masses for samples of active galactic nuclei (AGN) are currently estimated from single-epoch optical spectra. In particular, the size of the broad-line emitting region needed to compute the black hole mass is derived from the…