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Browsing IIAP Publications by Subject "Quasars"

Browsing IIAP Publications by Subject "Quasars"

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  • Anomalous heating of quasar emission-line regions 
    Krishan, V (Royal Astronomical Society, 1987-06)
    It is shown that the non-thermal radio radiation from a quasar is intense enough to drive parametric instabilities in the fully ionized emission-line regions. These instabilities cause significant enhancement of the plasma ...
  • Anomalous redshifts of quasi-stellar objects 
    Narlikar, J. V; Das, P. K (American Astronomical Society, 1980-09)
    This paper is based on the assumption that the observational evidence to date does point to the possibility that high-redshift quasars are physically associated with low-redshift galaxies. It is first argued that the excess ...
  • 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 ...
  • A central gravitational redshift model for the absorption redshift systems in quasi-stellar objects 
    Das, P. K (Royal Astronomical Society, 1979-01)
    Static, spherically symmetric configurations of core and envelope type have been considered in General Relativity as central gravitational redshift models for the quasi-stellar objects (QSOs) and an attempt has been made ...
  • Ejection of massive black holes from galaxies 
    Kapoor, R. C (Indian Academy of Sciences, 1976-11)
    Gravitational recoil of a gigantic black hole of about 10 to the 8th to 10 to the 9th solar masses formed in the nonspherical collapse of the nuclear part of a typical galaxy can take place with an appreciable speed as a ...
  • High-redshift narrow-line Seyfert 1 galaxies: a candidate sample 
    Rakshit, S; Stalin, C. S; Kotilainen, Jari; Shin, Jaejin (IOP Publishing, 2021-03)
    The study of narrow-line Seyfert 1 galaxies (NLS1s) is now mostly limited to low redshift (z < 0.8) because their definition requires the presence of the Hβ emission line, which is redshifted out of the spectral coverage ...
  • Is 21-cm absorption associated with the emission-line regions of quasars? 
    Krishan, V (Royal Astronomical Society, 1988-03)
    The 21-cm absorption line observed in several QSO systems is believed to originate in neutral hydrogen clouds in the vicinity of the QSOs. The aim of this paper is to show that 21-cm absorption can also originate in a ...
  • Long-term optical flux and colour variability in quasars 
    Sukanya, N; Stalin, C. S; Jeyakumar, S; Praveen, D; Dhani, A; Damle, R (IOP Publishing, 2016-02)
    We have used optical V and R band observations from the Massive Compact Halo Object (MACHO) project on a sample of 59 quasars behind the Magellan ic clouds to study their long term optical flux and colour ...
  • Near-infrared and optical imaging of Q2345+007: The largest gravitationally lensed QSO system? 
    Gopal-Krishna; Yates, M; Wiita, P. J; Smette, A; Pati, A. K; Altieri, B (The European Southern Observatory, 1993-12)
    We have taken K, R, V, and B band images of Q 2345+007, which has been claimed to be the gravitationally lensed quasar with the widest separation between the two images (approximately equal 7 arcsec), although the lens ...
  • On the hypothesis of ejection of supermassive black holes from centers of galaxies and its application to quasar-galaxy associations 
    Kapoor, R. C (D. Reidel Publishing Co., 1983-06)
    It is argued that accreting supermassive black holes ejected from centers of galaxies are the likely models for the quasars observed in association with galaxies. Also pointed out are the implications of a recent suggestion ...
  • Polarization and QPOs from jets in black hole systems 
    Mangalam, A (Indian Academy of Sciences, 2018-12)
    The historical observations of polarized jet emission for Blazars are reviewed and previous models are discussed. Motivated by this, a model for polarization of both steady and transient behavior using a helical magnetic ...
  • Quasar catalogue for the astrometric calibration of the forthcoming ILMT survey 
    Mandal, A. K; Pradhan, Bikram; Surdej, Jean; Stalin, C. S; Sagar, R; Mathew, B (Indian Academy of Sciences, 2020-12)
    Quasars are ideal targets to use for astrometric calibration of large scale astronomical surveys as they have negligible proper motion and parallax. The forthcoming 4-m International Liquid Mirror Telescope (ILMT) will ...
  • Radio wave heating of astrophysical plasmas 
    Gangadhara, R. T; Krishan, V (Indian Academy of Sciences, 1990-12)
    The coherent plasma process, parametric decay instability (PDI), has been applied to a homogeneous and unmagnetized plasma. These instabilities cause anomalous absorption of strong electromagnetic radiation under specific ...
  • Raman scattering of the synchrotron self-absorbed radiation in accretion discs 
    Krishan, V (Royal Astronomical Society, 1988-01)
    The quasar non-thermal continuum in the radio region can undergo Raman scattering in the accretion disc plasma around the central black hole provided that the frequency and the wave vector matching and the threshold ...
  • 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 ...
  • The role of Compton and Raman scattering in the quasar continuum 
    Gangadhara, R. T; Krishan, V (Blackwell Publishing, 1992-05)
    There are three ways in which an electromagnetic wave can undergo scattering in a plasma: (1) when the scattering of radiation occurs by a single electron, it is called Compton Scattering; (2) if it occurs by a longitudinal ...
  • Scattering of quasar radiation in intercloud plasma 
    Krishan, V (Royal Astronomical Society, 1988-09)
    Three different levels of description are available to describe the interaction of electromagnetic radiation with electrons in a fully ionized plasma: stimulated Raman scattering, stimulated Compton scattering, and Compton ...
  • A search for intra-night optical variability in radio-quiet QSOs 
    Gopal-Krishna; Sagar, R; Witta, P. J (Royal Astronomical Society, 1993-06-15)
    We report results from a new program, using the 2.34-m Vainu Bappu Telescope, to search for intra-night optical variability in five QSOs which are radio-quiet but optically bright and luminous. Our limited data show mild ...
  • The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release 
    Lyke, Brad W; Higley, Alexandra N; McLane, J. N; Schurhammer, D. P; Myers, A. D; Ross, A. J; Dawson, K; Chabanier, S; Martini, P; Busca, N. G; Mas des Bourboux, Helion du; Salvato, Mara; Streblyanska, A; Zarrouk, P; Burtin, E; Anderson, S. F; Bautista, J; Bizyaev, D; Brandt, W. N; Brinkmann, J; Brownstein, J. R; Comparat, J; Green, Paul; de la Macorra, Axel; Munoz Gutierrez, Andrea; Hou, Jiamin; Newman, J. A; Palanque-Delabrouille, N; Paris, I; Percival, W. J; Petitjean, P; Rich, J; Rossi, G; Schneider, D. P; Smith, Alexander; Vivek, M; Weaver, Benjamin A (IOP Publishing, 2020-09)
    We present the final Sloan Digital Sky Survey IV (SDSS-IV) quasar catalog from Data Release 16 of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). This catalog comprises the largest selection of spectroscopically ...
  • Some constraints on quasar progenitors and quasar evolution 
    Sivaram, C (International Astronomical Union, 1986)

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