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Browsing IIAP Publications by Subject "Active galactic nuclei"

Browsing IIAP Publications by Subject "Active galactic nuclei"

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  • An accreting supermassive black hole buried in a faint dwarf galaxy 
    Paswan, Abhishek; Das, Mousumi; Rubinur, K (The American Astronomical Society, 2024-09-10)
    In the last decade, there have been several discoveries of active galactic nuclei (AGN) in dwarf galaxies including an AGN in an ultracompact dwarf galaxy with a black hole mass >106 Me. However, finding a supermassive ...
  • The Black Hole-Galaxy Connection: Interplay between Feedback, Obscuration, and Host Galaxy Substructure 
    Juneau, Stephanie; Goulding, Andy D; Banfield, Julie; Bianchi, Stefano; Duc, Pierre-Alain; Ho, I. -Ting; Dopita, Michael A; Scharwächter, Julia; Bauer, Franz E; Groves, Brent; Alexander, David M; Davies, Rebecca L; Elbaz, David; Freeland, Emily; Hampton, Elise; Kewley, Lisa J; Nikutta, Robert; Shastri, Prajval; Shu, Xinwen; Vogt, Frederic P. A; Wang, Tao; Wong, O. Ivy; Woo, Jong-Hak (American Astronomical Society, 2022-02-01)
    There is growing evidence for physical influence between supermassive black holes and their host galaxies. We present a case study of the nearby galaxy NGC 7582, for which we find evidence that galactic substructure plays ...
  • Breaks in the X-ray spectra of high-redshift blazars and the intervening medium 
    Gaur, Haritma; Mohan, Prashanth; Pandey, Ashwani (IOP Publishing, 2021-06-10)
    Flat-spectrum radio quasars (FSRQs) are a subclass of blazars characterized by prominent optical emission lines and a collimated large-scale jet along the observer's line of sight. An X-ray spectral flattening has been ...
  • CatNorth: An Improved Gaia DR3 Quasar Candidate Catalog with Pan-STARRS1 and CatWISE 
    Fu, Yuming; Wu, Xue-Bing; Li, Yifan; Pang, Yuxuan; Joshi, Ravi; Zhang, Shuo; Wang, Qiyue; Yang, Jing; Ng, FanLam; Liu, Xingjian; Qiu, Yu; Zhu, Rui; Wang, Huimei; Wolf, Christian; Zhang, Yanxia; Huo, Zhi-Ying; Ai, Y. L; Ma, Qinchun; Feng, Xiaotong; Bouwens, R. J (American Astronomical Society, 2024-04)
    A complete and pure sample of quasars with accurate redshifts is crucial for quasar studies and cosmology. In this paper, we present CatNorth, an improved Gaia Data Release 3 (Gaia DR3) quasar candidate catalog with more ...
  • Changing-look active galactic nuclei: a study of optical/uv and the highly ionized fe kα x-ray line flux variations using photoionization simulations 
    Adhikari, T. P; Mondal, Santanu; He, Zhicheng; Rozanska, Agata; Hryniewicz, K (American Astronomical Society, 2025-07-20)
    Significant variability in broad emission line strengths of active galactic nuclei (AGN) over months to years has been observed, often accompanied by intrinsic continuum changes. Such spectral variability challenges the ...
  • Characterizing the Optical Nature of the Blazar S5 1803+784 during Its 2020 Flare 
    Agarwal, A; Pandey, Ashwani; Ozdonmez, Aykut; Ege, Ergun; Avik, Kumar Das; Volkan, Karakulak (IOP Publishing, 2022-07-01)
    We report the results from our study of the blazar S5 1803+784 carried out using quasi-simultaneous B, V, R, and I observations from 2020 May to 2021 July on 122 nights. Our observing campaign detected a historically bright ...
  • Effect of the time spent by the photon in the absorbed state on the time-dependent transfer of radiation 
    Mohan Rao, D; Rangarajan, K. E; Peraiah, A (The American Astronomical Society, 1990-08)
    The time-dependent transfer equation is derived for a two-level atomic model which takes both bound-bound and bound-free transitions into account. A numerical scheme is proposed for solving the monochromatic time-dependent ...
  • Evidence for Low-power Radio Jet–ISM Interaction at 10 pc in the Dwarf AGN Host NGC 4395 
    Nandi, Payel; Stalin, C. S; Saikia, D. J; Riffel, Rogemar A; Manna, Arijit; Pal, Sabyasachi; Dors, O. L; Wylezalek, Dominika; Paliya, Vaidehi S; Saikia, Payaswini; Dabhade, Pratik; Patig, Markus-Kissler; Sagar, R (American Astronomical Society, 2023-12-20)
    Black-hole-driven outflows in galaxies hosting active galactic nuclei (AGN) may interact with their interstellar medium (ISM) affecting star formation (SF). Such feedback processes, reminiscent of those seen in ...
  • Exploring the central region of NGC 1365 in the ultraviolet domain 
    Kurian, K. S; Stalin, C. S; Wylezalek, D; Lyubenova, Mariya; Adhikari, T. P; Devaraj, A; Sagar, R; Kissler-Patig, Markus; Mondal, Santanu (American Astronomical Society, 2024-10-10)
    Active galactic nuclei (AGN) feedback and its impact on their host galaxies are critical to our understanding of galaxy evolution. Here, we present a combined analysis of new high resolution ultraviolet (UV) data from the ...
  • Kinetic Equilibria of Accretion Discs 
    Bhaskaran, P; Krishan, V (Springer, 1995-10)
    A kinetic description of the equilibrium structure of accretion disc plasma is presented. It is possible to have an equilibrium configuration for a stationary axisymmetric gravitating plasma disc with spatial gradients in ...
  • Long-Term Monitoring of Blazar PKS 0208-512: A Change of γ-Ray Baseline Activity from EGRET to Fermi Era 
    Ammenadka, Krishna Mohana; Bhattacharya, Debbijoy; Bhattacharyya, Subir; Bhatt, N; Stalin, C. S (Multidisciplinary Digital Publishing Institute, 2022-10)
    The blazar PKS 0208-512 was in the lowest 𝛾 -ray brightness state during the initial 10 years of observations with the Fermi Gamma-ray Space Telescope (Fermi), which was an order of magnitude lower than its flux state ...
  • The modulation of radiation in an electron-positron plasma 
    Gangadhara, R. T; Krishan, V; Shukla, P. K (Royal Astronomical Society, 1993-05-01)
    The modulational instability of a large-amplitude, linearly polarized electromagnetic wave propagating in an electron-positron plasma is considered, including the combined effect of relativistic mass variation of the plasma ...
  • NGC 7314: X-ray study of the evolving accretion properties 
    Chatterjee, Debjit; Jana, Arghajit; Mangalam, A; Chang, Hsiang-Kuang (American Astronomical Society, 2024-11-20)
    We present a comprehensive analysis of the timing and spectral properties of NGC 7314, a Seyfert 1.9 galaxy, using X-ray observations from XMM-Newton, NuSTAR, and RXTE/proportional counter array (PCA). The timing analysis ...
  • On the properties of X-Ray corona in Seyfert 1 galaxies 
    Pal, Indrani; Anju, A; Sreehari, H; Rameshan, Gitika; Stalin, C. S; Ricci, Claudio; Marchesi, S (American Astronomical Society, 2024-11-20)
    We carried out a uniform and systematic analysis of a sample of 112 nearby bright Seyfert 1 type active galactic nuclei, the observations of which were carried out by the Nuclear Spectroscopic Telescope Array between 2013 ...
  • Revisiting the Dust Torus Size–Luminosity Relation Based on a Uniform Reverberation-mapping Analysis 
    Mandal, Amit Kumar; Woo, Jong-Hak; Wang, Shu; Rakshit, Suvendu; Cho, Hojin; Son, Donghoon; Stalin, C. S (2024-06-20)
    We investigate the torus size–luminosity relation of Type 1 active galactic nuclei (AGNs) based on the reverberation-mapping analysis using the light curves of the optical continuum and the IR continuum obtained with the ...
  • Simultaneous x-ray and optical polarization observations of the blazar Mrk 421 
    Bharathan, Athira M; Stalin, C. S; Sahayanathan, S; Wani, Kiran; Mandal, A. K; Chatterjee, Rwitika; Joshi, Santosh; Pandey, J. C; Mathew, B; Agrawal, V. K (American Astronomical Society, 2024-11-10)
    We present near-simultaneous X-ray and optical polarization measurements in the high synchrotron peaked (HSP) blazar Mrk 421. The X-ray polarimetric observations were carried out using Imaging X-ray Polarimetry Explorer ...
  • Spectrophotometric reverberation mapping of intermediate-mass black hole NGC 4395 
    Pandey, Shivangi; Rakshit, S; Chand, Krishan; Stalin, C. S; Cho, Hojin; Woo, Jong-Hak; Jalan, P; Mandal, A. K; Omar, A; Jose, Jincen; Gupta, Archana (American Astronomical Society, 2024-11-20)
    Understanding the origins of massive black hole seeds and their coevolution with their host galaxy requires studying intermediate-mass black holes (IMBHs) and estimating their mass. However, measuring the masses of these ...
  • Star Formation in the Dwarf Seyfert Galaxy NGC 4395: Evidence for Both AGN and SN Feedback? 
    Nandi, Payel; Stalin, C. S; Saikia, D. J; Muneer, S; Mountrichas, George; Wylezalek, D; Sagar, R; Patig, M. K (American Astronomical Society, 2023-06-20)
    We present a detailed multiwavelength study of star formation in the dwarf galaxy NGC 4395, which hosts an active galactic nucleus (AGN). From our observations with the Ultra-Violet Imaging Telescope, we have compiled a ...
  • Stimulated raman scattering in active galactic nuclei 
    Krishan, V; Wiita, P. J (International Astronomical Union, 1986)
    Stimulated Raman Scattering (SRS) processes offer an attractive and efficient method for producing both essentially the entire non-thermal continuum as well as fast electrons in active galactic nuclei (AGN). In this picture, ...
  • Ultraviolet flux and spectral variability study of blazars observed with UVIT/AstroSat 
    Reshma, M; Agarwal, Aditi; Stalin, C. S; Joseph, P; Dagore, A; Mandal, A. K; Devaraj, A; Gudennavar, S. B (American Astronomical Society, 2024-11-01)
    Blazars, the peculiar class of active galactic nuclei, are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics ...

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