Related papers: A Method for Black Hole Mass Determination in Accr…
I review the status of observational determinations of central masses in nearby galactic nuclei. Results from a variety of techniques are summarized, including ground-based and space-based optical spectroscopy, radio VLBI measurements of…
We determine the mass of the black hole at the center of the spiral galaxy NGC 4258 by constructing axisymmetric dynamical models of the galaxy. These models are constrained by high spatial resolution imaging and long-slit spectroscopy of…
We investigate the relationship between black hole mass (MBH) and Doppler boosted emission for BL Lacertae type objects (BL Lacs) detected in the SDSS and FIRST surveys. The synthesis of stellar population and bidimensional decomposition…
To test the idea that ultraluminous X-ray sources (ULXs) in external galaxies represent a class of accreting intermediate-mass black holes (IMBHs), we have undertaken a program to identify ULXs and a lower luminosity X-ray comparison sample…
We describe a program that we have embarked on to estimate the spins of stellar-mass black holes in X-ray binaries. We fit the continuum X-ray spectrum of the radiation from the accretion disk using the standard thin disk model, and extract…
We present spatially extended gas kinematics at parsec-scale resolution for the nuclear regions of four nearby disk galaxies, and model them as rotation of a gas disk in the joint potential of the stellar bulge and a putative central black…
Current astrophysical research suggests that the most persistently luminous objects in the Universe are powered by the flow of matter through accretion disks onto black holes. Accretion disk systems are observed to emit copious radiation…
We study the possibility of identifying dark matter in the galactic center from the physical properties of the electromagnetic radiation emitted from a optical-thin disk region around a static and spherically symmetric black hole. In…
We have embarked in an HST program to determine the masses of black holes in spiral galaxies directly by measuring the line emission arising from an extended accretion disk. For each of the galaxies in our sample we have measured the…
Black hole mass is a fundamental property of active galactic nuclei (AGNs). In the distant universe, black hole mass is commonly estimated using the MgII, Hbeta, or Halpha emission line widths and the optical/UV continuum or line…
The accretion flow in the disk dominated state of black hole binaries has peak temperature and luminosity which vary together in such a way as to indicate an approximately constant emitting area. The association of this with the last stable…
In our previous work, using luminosity and the H-beta FWHM as surrogates for black hole mass (M_BH), we compared the black hole masses of narrow-line Seyfert 1 galaxies (NLS1s) and broad-line Seyfert 1 galaxies (BLS1s) in a sample of soft…
The interaction of a supermassive black hole with the matter of an accretion disk in the presence of a magnetic field is the key mechanism of energy release in active galactic nuclei. However, determining the physical parameters of this…
We present our analysis of the high-energy radiation from black hole (BH) transients, using archival data obtained primarily with RXTE observatory, and a comprehensive test of the bulk motion Comptonization (BMC) model for the high-soft…
The nature of ultra-luminous X-ray sources (ULXs) has long been plagued by an ambiguity about whether the central compact objects are intermediate-mass (IMBH, >~ 10^3 M_sun) or stellar-mass (a few tens M_sun) black holes (BHs). The high…
The spins of a number of supermassive and stellar-mass black holes have been measured based on detections of thermal continuum emission and relativistically broadened iron lines in their x-ray spectra. Likewise, quasiperiodic variability…
We investigate the evolution of the properties of model populations of ultraluminous X-ray sources (ULXs) consisting of a black-hole accretor in a binary with a donor star. We have computed models corresponding to three different…
The supermassive black hole at the center of a distant galaxy can be weighed, in rare but realistic cases, when the galaxy acts as a strong gravitational lens. The central image that should be produced by the lens is either destroyed or…
Mass distribution of black holes in low-mass X-ray binaries previously suggested the existence of a $ \sim 2-5M_{\odot} $ mass gap between the most massive neutron stars and the least massive black holes, while some recent evidence appears…
We model the spectral energy distribution of the type 1 Seyfert galaxy NGC 5548, fitting data from simultaneous optical, UV, and X-ray monitoring observations. We assume a geometry consisting of a hot central Comptonizing region surrounded…