Related papers: Black hole mass estimate in OJ 287 based on the bu…
Supermassive black holes are common in centers of galaxies. Among the active galaxies, quasars are the most extreme, and their black hole masses range as high as to $6\cdot 10^{10} M_\odot$. Binary black holes are of special interest but so…
We present the results of long-term photometric monitoring of two active galactic nuclei, 2MASX J08535955+7700543 (z $\sim$ 0.106) and VII Zw 244 (z $\sim$ 0.131), being investigated by the reverberation mapping method in medium-band…
We discuss masses of stellar black holes found in binary systems and errors in their determination. The observed mass distribution has a broad shape within the range $4-16 M_\odot$ without visible concentration to some preferred value. On…
We present the results of X-ray variability and spectral analysis of a sample of 15 new candidates for active galactic nuclei with relatively low-mass black holes (BHs). They are selected from the Second XMM-Newton Serendipitous Source…
There are very few confirmed black holes with a mass that could be $\sim\! 4\, M_\odot$ and no neutron stars with masses greater than $\sim\! 2\, M_\odot$, creating a gap in the observed distribution of compact star masses. Some black holes…
We propose a methodology to derive a black-hole mass for super-critical accretion flow. Here, we use the extended disk blackbody (extended DBB) model, a fitting model in which the effective temperature profile obeys the relation $T_{\rm…
An empirical relation between the broad line region (BLR) size and optical continuum luminosity is often adopted to estimate the BLR size and then the black hole mass of AGNs. However, optical luminosity may not be a good indicator of…
Estimation of the black hole mass in bright X-ray sources of nearby galaxies is crucial to the understanding of these systems and their formation. However, the present allowed black hole mass range spans five order of magnitude (10Msun < M…
We present a summary of the results of the OJ 287 observational campaign, which was carried out during the 2021/2022 observational season. This season is special in the binary model because the major axis of the precessing binary happens to…
We present the results of our optical monitoring of the BL Lacertae object OJ 287 during the first half of 2005. The source did not show large-amplitude variations during this period and was in a relatively quiescent state. A possible…
We combine time-dependent multi-waveband flux and linear polarization observations with sub-milliarcsecond-scale polarimetric images at lambda=7mm of the BL Lacertae-type blazar OJ287 to locate the gamma-ray emission in prominent flares in…
We investigate low-density accretion flows onto massive black holes (BHs) with masses of $\gtrsim 10^5~M_\odot$ orbiting around in the outskirts of their host galaxies, performing three-dimensional hydrodynamical simulations. Those…
The correlation between black hole mass M(BH) and the central stellar velocity dispersion sigma in nearby elliptical galaxies affords a novel way to determine M(BH) in active galaxies. We report on measurements of sigma from optical spectra…
We investigate the relation between black hole (BH) mass and bulge stellar mass for a sample of 117 local ($z \sim 0$) galaxies hosting low-luminosity, broad-line active galactic nuclei (AGN). Our sample comes from Reines & Volonteri…
The rising phase of the 2023-24 outburst of the recently discovered bright transient black hole candidate Swift J1727.8-1613 was monitored by {\it Insight}-HXMT. We study the evolution of hard ($4$-150$ keV) and soft ($2$-$4$ keV) band…
The velocity dispersion of 7 Seyfert 1 galaxies at z~0.37 is measured using high signal-to-noise Keck spectra. Black hole (BH) mass estimates are obtained via an empirically calibrated photoionization method. We derive the BH mass velocity…
Motivated by the large body of literature around the phenomenological properties of accreting black hole (BH) and neutron star (NS) X-ray binaries in the radio:X-ray luminosity plane, we carry out a comparative regression analysis on 36 BHs…
We report the re-emergence of a new broadband emission through a detailed and systematic study of the multi-wavelength spectral and temporal behavior of OJ 287 after its first-ever reported VHE activity in 2017 to date, which includes the…
We make use of two empirical relations between the black hole mass and the global properties (bulge luminosity and stellar velocity dispersion) of nearby elliptical galaxies, to infer the mass of the central black hole (M_BH) in low…
Aims. The black hole binary SWIFT J1753.5-0127 is providing a unique data set to study accretion flows. Various investigations of this system and of other black holes have not, however, led to an agreement on the accretion flow geometry or…