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Browsing by Author "Mangalam, A"

Browsing by Author "Mangalam, A"

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  • Eccentric equatorial trajectories around a Kerr black hole asa QPO model for M82X-1 
    Prerna Rana; Mangalam, A (World Scientific Publishing, 2022)
    We study the bound orbit conditions for equatorial and eccentric orbits around a Kerrblack hole both in the parameter space (E,L,a) representing the energy, angular mo-mentum of the test particle, and spin of the black ...
  • Energy distribution of solar flare events 
    Sen, Samrat; Mangalam, A; Ramesh, R (Cambridge University Press, 2018-02)
    The coronal field typically reorganizes itself to attain a force-free field configuration. We have evaluated the power law index of the energy distribution f(E) = f0E−α by using a model of relaxation incorporating ...
  • Evolution of the M•-σ relation 
    Bhattacharyya, D; Mangalam, A (Cambridge University Press, 2018-05)
    Black holes at the centers of the galaxies grow mainly by the processes of accretion, mergers, and consumption of stars. In the case of gas accretion with cooling sources, the flow is momentum driven, after which the black ...
  • Flux tube model in the solar atmosphere 
    Sen, Samrat; Mangalam, A (Cambridge University Press, 2018-02)
    We construct two classes of the magnetohydrostatic equilibria of the axisymmetric flux tubes with twisted magnetic fields in the stratified solar atmosphere that span from the photosphere to the transition region. We built ...
  • Formation of a proto-quasar from accretion flows in a halo 
    Mangalam, A (E D P Sciences, 2001-12)
    We present a detailed model for the formation of massive objects at the centers of galaxies. The effects of supernovae heating and the conditions of gas loss are revisited. The escape time of the gas is compared with the ...
  • Frequency-dependent core shifts and parameter estimation for the blazar 3C 454.3 
    Mohan, Prashanth; Agarwal, A; Mangalam, A; Gupta, A. C; Wiita, P. J; Volvach, A. E; Aller, M. F; Aller, H. D; Gu, M. F; Lahteenmaki, A; Tornikoski, M; Volvach, L. N (Oxford University Press on behalf of the Royal Astronomical Society, 2015-09-11)
    We study the core shift effect in the parsec-scale jet of the blazar 3C 454.3 using the 4.8– 36.8 GHz radio light curves obtained from three decades of continuous monitoring. From a piecewise Gaussian fit to each flare, ...
  • A Geometric Origin for Quasi-periodic Oscillations in Black Hole X-Ray Binaries 
    Prerna Rana; Mangalam, A (IOP Publishing, 2020-11-10)
    We expand the relativistic precession model to include nonequatorial and eccentric trajectories and apply it to quasi-periodic oscillations (QPOs) in black hole X-ray binaries (BHXRBs) and associate their frequencies with ...
  • A Global galactic dynamo with a corona constrained by relative helicity 
    Avijeet Prasad; Mangalam, A (IOP Publishing, 2016-01)
    We present a model for a global axisymmetric turbulent dynamo operating in a galaxy with a corona that treats the parameters of turbulence driven by supernovae and by magneto-rotational instability under a common ...
  • Kinematics of and emission from helically orbiting blobs in a relativistic magnetized jet 
    Mohan, Prashanth; Mangalam, A (IOP Publishing, 2015-07-01)
    We present a general relativistic (GR) model of jet variability in active galactic nuclei due to orbiting blobs in helical motion along a funnel or cone-shaped magnetic surface anchored to the accretion disk near the black ...
  • A model for relativistic disk emission, flow and variability 
    Mohan, Prashanth; Mangalam, A (Astronomical Society of India, 2015-04)
    Orbiting features near a black hole can cause variability in optical/UV and X-ray bands with quasi-periodic signatures. The variable flux is derived in Kerr geometry including the following relativistic effects: light ...
  • Model of a fluxtube with a twisted magnetic field in the stratified solar atmosphere 
    Sen, Samrat; Mangalam, A (Elsevier B.V, 2018-01-15)
    We build a single vertical straight magnetic fluxtube spanning the solar photosphere and the transition region which does not expand with height. We assume that the fluxtube containing twisted magnetic fields is in ...
  • Models of Flux Tubes from Constrained Relaxation 
    Mangalam, A; Krishan, V (Indian Academy of Sciences, 2000-12)
    We study the relaxation of a compressible plasma to an equilibrium with flow. The constraints of conservation of mass, energy, angular momentum, cross-helicity and relative magnetic helicity are imposed. Equilibria ...
  • Models of force-free spheres and applications to solar active regions 
    Avijeet Prasad; Mangalam, A (Astronomical Society of India, 2013)
    Here we present a systematic study of force-free field equation for simple axisymmetric configurations in spherical geometry. The condition of separability of solutions in radial and angular variables leads to two classes ...
  • Multiwavelength intraday variability of the BL Lacertae S5 0716+714 
    Gupta, A. C; Krichbaum, T. P; Wiita, P. J; Rani, B; Sokolovsky, K. V; Mohan, Prashanth; Mangalam, A; Marchili, N; Fuhrmann, L; Agudo, I; Bach, U; Bachev, R; Böttcher, M; Gabanyi, K. E; Gaur, H; Hawkins, K; Kimeridze, G. N; Kurtanidze, O. M; Kurtanidze, S. O; Lee, C.-U; Liu, X; McBreen, B; Nesci, R; Nestoras, G; Nikolashvili, M. G; Ohlert, J. M; Palma, N; Peneva, S; Pursimo, T; Semkov, E; Strigachev, A; Webb, J. R; Wiesemeyer, H; Zensus, J. A (Wiley-Blackwell, 2012-09)
    We report results from a one-week multiwavelength campaign to monitor the BL Lacertae object (BL Lac) S5 0716+714 (on 2009 December 9–16). Nine ground-based telescopes at widely separated longitudes and one space-based ...
  • M∙ − σ relation in spherical systems 
    Bhattacharyya, D; Mangalam, A (Indian Academy of Sciences, 2018-02)
    To investigate the M∙−σ relation, we consider realistic elliptical galaxy profiles that are taken to follow a single power-law density profile given by Ï (r)=Ï 0(r/r0)−γ or the Nuker intensity profile. We calculate ...
  • On the injection spectrum of relativistic electrons in high-redshift radio galaxies 
    Gopal-Krishna; Mhaskey, Mukul; Mangalam, A (IOP Publishing, 2012-01-01)
    We point out that the remarkable linearity of the ultra-steep radio spectra of high redshift radio galaxies re ects a previously reported general trend for powerful radio galaxies, according to which the spectral curvature ...
  • Open and closed magnetic configurations of twisted flux tubes 
    Sen, Samrat; Mangalam, A (IOP Publishing, 2019-06-01)
    We construct two classes of magnetohydrostatic (MHS) equilibria for an axisymmetric vertical flux tube spanning from the photosphere to the lower part of the transition region within a realistic stratified solar atmosphere ...
  • Orbital signatures from observed light curves of blazars 
    Mangalam, A; Mohan, Prashanth (Indian Academy of Sciences, 2014-04)
    Variability in active galactic nuclei is observed in ultraviolet to X-ray emission based light curves. This could be attributed to orbital signatures of the plasma that constitutes the accretion flow on the putative disk ...
  • Parametric models of the periodogram 
    Mohan, Prashanth; Mangalam, A; Chattopadhyay, S (Indian Academy of Sciences, 2014-04)
    The maximum likelihood estimator is used to determine fit parameters for various parametric models of the Fourier periodogram followed by the selection of the best fit model amongst competing models using the Akaike ...
  • Parsec-scale jet properties of the quasar PG 1302-102 
    Mohan, P; An, T; Frey, S; Mangalam, A; Gabanyi, K. E; Kun, E (Oxford University Press on behalf of the Royal Astronomical Society, 2016-12-01)
    The quasar PG 1302−102 is believed to harbour a supermassive binary black hole (SMBBH) system. Using the available 15 GHz and 2–8 GHz, multi-epoch Very Long Baseline Array data, we constrain the pc-scale jet properties ...

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