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Browsing by Subject "Active galactic nuclei"

Browsing by Subject "Active galactic nuclei"

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  • 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 ...
  • Coordinated TeV gamma-ray and optical polarization study of BL Lac object Mkn 501 
    Joshi, U. C; Baliyan, K. S; Ganesh, S; Deshpande, M. R; Bhattacharyya, S; Kaul, R. K; Kaul, C. L; Bhat, C. L (Astronomical Society of India, 2000)
    Coordinated TeV gamma-ray and optical polarization observations of the BL Lac object Mkn 501, carried out during 1997 with the TACTIC imaging Cerenkov telescope of the BARC and the 1.2 m Gurushikhar optical/IR telescope ...
  • 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 ...
  • Energetics of a Kerr blackhole in electromagnetic fields: Role of the relative angular velocity of charged particles 
    Parthasarathy, S; Dhurandhar, S. V; Dadhich, N (Astronomical Society of India, 1985-06)
  • 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 ...
  • An Expanding Plasma Model for the X-ray/radio knots in KPC-scale Jets of Active Galactic Nuclei 
    Sahayanathan, S; Misra, R; Kembhavi, A. K; Kaul, C. L (Astronomical Society of India, 2003)
    We model the observed X-ray/radio knots in Active Galactic Nuclei (AGN) as isotropically expanding spherical plasma clouds fed continously by non-thermal electrons. The time-dependent electron distribution and the emitted ...
  • 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 ...
  • 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 ...
  • Seyferts at milli-arcsec scales 
    Lal, D. V; Shastri, P; Gabuzda, D (Astronomical Society of India, 2000)
    We have observed a sample of Seyfert galaxies using Global Very Long Baseline Interferometry at 5 GHz. Our goal is to investigate the systematics of their nuclear radio morphology on milli-arcsecond scales. We have chosen ...
  • 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, ...
  • 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 ...
  • X-Ray Spectral Variability of the Seyfert Galaxy NGC4593 
    Ghosh, K. K; Soundararajaperumal, S (European Southern Observatory, 1993-06)
    X-ray (0.1-10 keV) spectra of NGC 4593 were obtained with EXOSAT on seven epochs between 1984 and 1986 using the low and medium energy detectors. Detailed results of the spectral analysis of the seven spectra (obtained ...
  • X-ray spectrum of the radio-loud quasar PKS 1217 + 023 
    Ghosh, K. K; Soundararajaperumal, S (EDP Sciences, 1991-12)
    A study of the X-ray (0.1-10 keV) spectrum from the radio-loud quasar, PKS 1217 + 023 is presented. This quasar was observed with Exosat on two epochs in January 29 and May 14, 1984. The data were obtained from the Exosat ...
  • The X-shaped Radio Galaxy J0725+5835 is Associated with an AGN Pair 
    Yang, Xiaolong; Ji, Jialu; Joshi, Ravi; Yang, Jun; An, Tao; Wang, Ran; Ho, Luis C; Roberts, David H; Saripalli, Lakshmi (IOP Publishing, 2022-07-01)
    X-shaped radio galaxies (XRGs) are those that exhibit two pairs of unaligned radio lobes (main radio lobes and wings). One of the promising models for the peculiar morphology is jet reorientation. To clarify this, we ...

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