Browsing FAS Scholarly Articles by Keyword "accretion disks"

Now showing items 1-11 of 11

    • Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets 

      McClintock, Jeffrey E.; Narayan, Ramesh; Steiner, James (Springer Science + Business Media, 2013)
      The spins of ten stellar black holes have been measured using the continuum- fitting method. These black holes are located in two distinct classes of X-ray binary systems, one that is persistently X-ray bright and another ...

    • The constant inner-disk radius of LMC X-3: A basis for measuring black hole spin 

      Steiner, James; McClintock, Jeffrey E.; Remillard, Ronald A.; Gou, Lijun; Yamada, Shin; Narayan, Ramesh (IOP Publishing, 2010)
      he black hole binary system LMC X-3 has been observed by virtually every X-ray mission since the inception of X-ray astronomy. Among the persistent sources, LMC X-3 is uniquely both habitually soft and highly variable. ...

    • The flare activity of Sagittarius A* 

      Eckart, A.; Baganoff, F. K.; Schödel, R.; Morris, M.; Genzel, R.; Bower, G. C.; Marrone, D.; Moran, James M.; Viehmann, T.; Bautz, M. W.; Brandt, W. N.; Garmire, G. P.; Ott, T.; Trippe, S.; Ricker, G. R.; Straubmeier, C.; Roberts, D. A.; Yusef-Zadeh, F.; Zhao, Jun-Hui; Rao, Ramprasad (EDP Sciences, 2006)
      Context. We report new simultaneous near-infrared/sub-millimeter/X-ray observations of the SgrA* counterpart associated with the massive 3–4×106M⊙ black hole at the Galactic Center. Aims. The main aim is to investigate the ...

    • The GALEX Time Domain Survey. II. Wavelength-Dependent Variability of Active Galactic Nuclei in the Pan-STARRS1 Medium Deep Survey 

      Hung, T; Gezari, S; Jones, D.O.; Kirshner, Robert P.; Chornock, R; Berger, Edo; Rest, A.; Huber, M.; Narayan, G.; Scolnic, D.; Waters, C.; Wainscoat, R.; Martin, D.C.; Forster, K.; Neill, J.D. (American Astronomical Society, 2016)
      We analyze the wavelength-dependent variability of a sample of spectroscopically confirmed active galactic nuclei (AGN) selected from near-UV (NUV) variable sources in the GALEX Time Domain Survey that have a large amplitude ...

    • Hot Accretion Flows Around Black Holes 

      Yuan, Feng; Narayan, Ramesh (Annual Reviews, 2014)
      Black hole accretion flows can be divided into two broad classes: cold and hot. Cold accretion flows, which consist of cool optically thick gas, are found at relatively high mass accretion rates. Prominent examples are the ...

    • Location of the bow shock ahead of cloud G2 at the Galactic Centre 

      Sadowski, A.; Narayan, Ramesh; Sironi, L.; Ozel, F. (Oxford University Press (OUP), 2013)
      We perform detailed magnetohydrodynamic simulations of the gas cloud G2 interacting with the accretion flow around the Galactic Center black hole Sgr A∗ . We take as our initial conditions a steady-state, converged solution ...

    • Measuring the Spins of Stellar Black Holes: A Progress Report 

      McClintock, Jeffrey E.; Narayan, Ramesh; Gou, L.; Liu, J.; Penna, R; Steiner, J; Comastri, A.; Angelini, L.; Cappi, Marina Christine (American Institute of Physics, 2010)
      We use the Novikov-Thorne thin disk model to fit the thermal continuum X-ray spectra of black hole X-ray binaries, and thereby extract the dimensionless spin parameter a∗=a/M of the black hole as a parameter of the fit. ...

    • Ps1-10jh Continues to Follow the Fallback Accretion Rate of a Tidally Disrupted Star 

      Gezari, S.; Chornock, R.; Lawrence, A.; Rest, A.; Jones, D. O.; Berger, Edo; Challis, P. M.; Narayan, G. (IOP Publishing, 2015)
      We present late-time observations of the tidal disruption event candidate PS1-10jh. UV and optical imaging with HST/WFC3 localize the transient to be coincident with the host galaxy nucleus to an accuracy of 0.023 arcsec, ...

    • Radio light curves during the passage of cloud G2 near Sgr A* 

      Sadowski, A.; Sironi, L.; Abarca, D.; Guo, X.; Ozel, F.; Narayan, Ramesh (Oxford University Press (OUP), 2013)
      We calculate radio light curves produced by the bow shock that is likely to form in front of the G2 cloud when it penetrates the accretion disk of Sgr A∗ . The shock acceleration of the radioemitting electrons is captured ...

    • The structure of the accretion disk in NGC 4258 

      Moran, James M.; Humphreys, Elizabeth; Greenhill, Lincoln Jared; Reid, Mark Jonathan; Argon, Alice (Cambridge University Press (CUP), 2007)
      A wealth of new information about the structure of the maser disk in NGC 4258 has been obtained from a series of 18 VLBA observations spanning three years, as well as from 32 additional epochs of spectral monitoring data ...

    • Toward a New Geometric Distance to the Active Galaxy NGC 4258. II. Centripetal Accelerations and Investigation of Spiral Structure 

      Humphreys, E. M. L.; Reid, Mark Jonathan; Greenhill, Lincoln J.; Moran, James M.; Argon, Alice L. (American Astronomical Society, 2008)
      We report measurements of centripetal accelerations of maser spectral components of NGC 4258 for 51 epochs spanning 1994 to 2004. This is the second paper of a series, in which the goal is the determination of a new geometric ...