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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 ...
  • 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 ...
  • Variability and the Size–Luminosity Relation of the Intermediate-mass AGN in NGC 4395 
    Cho, Hojin; Woo, Jong-Hak; Hodges-Kluck, E; Son, Donghoon; Shin, Jaejin; Gallo, Elena; Bae, Hyun-Jin; Brink, T. G; Cho, Wanjin; Filippenko, A. V; Horst, J. C; Ilic, Dragana; Joner, M. D; Kang, Daeun; Kang, Wonseok; Kaspi, Shai; Kim, Taewoo; Kovacevic, A. B; Kumar, S; Le, Huynh Anh N; Nadzhip, A. E; Nunez, F. P; Metlov, V. G; Oknyansky, V. L; Park, Songyoun; Popovic, L. C; Rakshit, S; Schramm, M; Shatsky, N. I; Spencer, M; Sung, E.-H; Sung, H.-i; Tatarnikov, A. M; Vince, O (IOP Publishing, 2020-04-01)
    We present a variability study of the lowest-luminosity Seyfert 1 nucleus of the galaxy NGC 4395 based on photometric monitoring campaigns in 2017 and 2018. Using 22 ground-based and space telescopes, we monitored NGC ...

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