Related papers: Supermassive Black Hole Binary Candidates from the…
A list of candidates for \textit{supermassive binary black holes} (SMBBHs), compiled from available data on the variability in the optical range and the shape of the emission spectrum, is analysed. An artificial neural network is…
We report the identification of 64 new candidates of compact galaxies, potentially hosting faint quasars with bolometric luminosities of $L_\mathrm{bol} = 10^{43}$--10$^{46}$ erg s$^{-1}$, residing in the reionization epoch within the…
Supermassive black hole binaries (SMBHs) are expected to result from galaxy mergers, and thus are natural byproducts (and probes) of hierarchical structure formation in the Universe. They are also the primary expected source of…
We present analysis of Chandra X-ray observations of seven quasars that were identified as candidate sub-parsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey (CRTS) based on apparent periodicity in…
Quasars whose broad emission lines show temporal, bulk radial velocity (RV) shifts have been proposed as candidate sub-parsec (sub-pc), binary supermassive black holes (BSBHs). We identified a sample of 16 BSBH candidates based on two-epoch…
Supermassive black hole binaries (SMBHBs) should be common in galactic nuclei as a result of frequent galaxy mergers. Recently, a large sample of sub-parsec SMBHB candidates was identified as bright periodically variable quasars in optical…
We perform a systematic search for sub-parsec binary supermassive black holes (BHs) in normal broad line quasars at z<0.8, using multi-epoch SDSS spectroscopy of the broad Hbeta line. Our working model is that: only one of the two BHs in…
Periodic quasars are candidates for binary supermassive black holes (BSBHs) efficiently emitting low frequency gravitational waves. Recently, $\sim$150 candidates were identified from optical synoptic surveys. However, they may be false…
In several previous studies, quasars exhibiting broad emission lines with >1000 km/s velocity offsets with respect to the host galaxy rest frame have been discovered. One leading hypothesis for the origin of these velocity-offset broad…
We present the results of a systematic search for massive black hole binaries in the Sloan Digital Sky Survey spectroscopic database. We focus on bound binaries, under the assumption that one of the black holes is active. In this framework,…
We present analysis of NuSTAR X-ray observations of three AGN that were identified as candidate subparsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey based on apparent periodicity in their…
Supermassive black hole (SMBH) binary systems are unavoidable outcomes of galaxy mergers. Their dynamics encode information about their formation and growth, the composition of their host galactic nuclei, the evolution of galaxies, and the…
Understanding the origin and evolution of supermassive black holes (SMBH) stands as one of the most important challenges in astrophysics and cosmology, with little current theoretical consensus. Improved observational constraints on the…
Supermassive binary black holes (SBBHs) are a natural outcome of galaxy mergers. Here we show that low-frequency ($f \leq 10^{-6}$ Hz) quasi-periodic variability observed from cosmic blazar sources can provide substantial inductive support…
Haystack and Owens Valley Radio Observatory (OVRO) observations recently revealed strong, intermittent, sinusoidal total flux-density variations that maintained coherence between 1975 and 2021 in the blazar PKS 2131$-$021 ($z=1.283$). This…
We present Hubble Space Telescope ultraviolet (UV) of 13 quasars at z<0.7, along with contemporaneous optical spectra from ground-based telescopes. The targets were selected to have broad H-beta emission lines with substantial velocity…
Here we consider the perspective to detect sub-pc super-massive binary black-hole (SMBBH) systems using long-term photometric and spectroscopic monitoring campaigns of active galactic nuclei. This work explores the nature of long-term…
Supermassive binary black holes at sub-parsec orbital separations have yet to be discovered, with the possible exception of blazar OJ~287. In parallel to the global hunt for nanohertz gravitational waves from supermassive binaries using…
We recently discovered a supermassive black hole binary (SMBHB) candidate, PKS J1309+1154, in the combined 46-yr University of Michigan Radio Astronomy Observatory (UMRAO) plus Owens Valley Radio Observatory (OVRO) blazar monitoring…
The role of mergers in the evolution of massive black holes is still unclear, and their dynamical evolution, from the formation of pairs to binaries and the final coalescence, carries large physical uncertainties. The identification of the…