Related papers: A supermassive binary black hole in the quasar 3C3…
Relativistic jets powered by stellar mass black holes in X-ray binaries appear to come in two types: steady outflows associated with hard X-ray states and large scale discrete ejections associated with transient outbursts. We show that the…
Very Long Baseline Interferometry (VLBI) allows for high-resolution and high-sensitivity observations of relativistic jets, that can reveal periodicities of several years in their structure. We perform an analysis of long-term VLBI data of…
Massive merging black holes will be the primary sources of powerful gravitational waves at low frequency, and will permit to test general relativity with candidate galaxies close to a binary black hole merger. In this paper we identify the…
We present a new type of observation relating the gravitational wave emission of supermassive black hole mergers to their electromagnetic counterparts. This dual emission involves variability of a relativistic jet arising from the…
The observations and theory of the exciting new class of galactic black hole X-ray transients is reviewed. Seven of these systems have measured mass functions or mass estimates in excess of stable neutron stars, making them excellent black…
Search for periodic signals from blazars has become widely discussed topic in recent years. In the scenario that such periodic changes originate from the innermost regions of blazars, the signals bear imprints of the processes occurring…
The geometry of the accretion flow around stellar-mass black holes can change on timescales of days to months. When a black hole emerges from quiescence (that is, it "turns on" after accreting material from its companion) it has a very hard…
The existence of binary supermassive black holes (SBHs) is predicted by models of hierarchical galaxy formation. To date, only a single binary SBH has been imaged, at a projected separation of 7.3 parsecs. Here we report the detection of a…
Quasi-periodic oscillations and X-ray spectroscopy are powerful probes of black hole masses and accretion disks, and here we apply these diagnostics to an ultraluminous X-ray source (ULX) in the spiral galaxy NGC628 (M74). This object was…
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…
Tests of Einstein's general theory of relativity have mostly been carried out in weak gravitational fields where the space-time curvature effects are first-order deviations from Newton's theory. Binary pulsars provide a means of probing the…
We consider the periodic modulation of emission from jets in blazar-type sources. A differential Doppler boosting origin, associated with the helical motion of a radiating component, is analyzed for different periodic driving sources…
The search for periodic signals from blazars has become an actively pursued field of research in recent years. This is because periodic signals bring us information about the processes occurring near the innermost regions of blazars, which…
Galactic black hole binaries produce powerful outflows with emit over almost the entire electromagnetic spectrum. Here, we report the first detection with the Herschel observatory of a variable far-infrared source associated with the…
Supermassive black hole binaries (SMBHs) are a fascinating byproduct of galaxy mergers in the hierarchical universe. In the last stage of their orbital evolution, gravitational wave radiation drives the binary inspiral and produces the…
We present our view of the immediate environment of an astrophysical black hole. We discuss the origin of the electron-positron and electron-proton jet components, and the origin of the large-scale magnetic field. We show how the aberrated…
Quasars shine brightly due to the liberation of gravitational energy as matter falls onto a supermassive black hole in the centre of a galaxy. Variations in the radiation received from active galactic nuclei (AGN) are studied at all…
Accretion disks around supermassive black holes in active galactic nuclei produce continuum radiation at ultraviolet and optical wavelengths. Physical processes in the accretion flow lead to stochastic variability of this emission on a wide…
We present a high-cadence multi-epoch analysis of dramatic variability of three broad emission lines (MgII, H$\beta$, and H$\alpha$) in the spectra of the luminous quasar ($\lambda L_{\lambda}$(5100\r{A}) = $4.7 \times 10^{44}$ erg…
We present a detailed study of a binary system of tailed radio galaxies which, along with 3C75, is the only such binary known to exist. The binary is located in a region of low galaxy density at the periphery of a poor cluster Abell S345,…