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Gopal-Krishna & Paul Joseph Wiita

Optical monitoring of Active Galactic Nuclei from ARIES

(Volume 87 - Année 2018 — Actes de colloques — First Belgo-Indian Network for Astronomy & Astrophysics (BINA) workshop - November 2016 - Nainital, India)
Open Access

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Mots-clés : AGN, astronomy, astrophysics, extragalactique, photométrie, visible


This overview provides a historical perspective highlighting the pioneering role which the fairly modest observational facilities of ARIES have played since the 1990s in systematically characterizing the optical variability on hour-like time scale (intra-night optical variability, or INOV) of several major types of high-luminosity Active Galactic Nuclei (AGN). Such information was previously available only for blazars. Similar studies have since been initiated in at least a dozen countries, giving a boost to AGN variability research.

Our work has, in particular, provided strong indication that mild INOV occurs in radio-quiet QSOs (amplitude up to ~ 3 – 5 % and duty cycle ~ 10%) and, moreover, has demonstrated that similarly mild INOV is exhibited even by the vast majority of radio-loud quasars which possess powerful relativistic jets (even including many that are beamed towards us). The solitary outliers are blazars, the tiny strongly polarized subset of powerful AGN, which frequently exhibit a pronounced INOV. Among the blazars, BL Lac objects often show a bluer-when-brighter chromatic behavior, while the flat spectrum radio quasars seem not to. Quantifying any differences of INOV among the major subclasses of non-blazar type AGNs will require dedicated monitoring programs using 2 - 3 metre class telescopes.

Keywords : AGN, astronomy, astrophysics, extragalactic, photometry, visible

To cite this article

Gopal-Krishna & Paul Joseph Wiita, «Optical monitoring of Active Galactic Nuclei from ARIES», Bulletin de la Société Royale des Sciences de Liège [En ligne], Volume 87 - Année 2018, Actes de colloques, First Belgo-Indian Network for Astronomy & Astrophysics (BINA) workshop - November 2016 - Nainital, India, 281 - 290 URL :

About:  Gopal-Krishna

Centre for Excellence in Basic Sciences, University of Mumbai Campus (Kalina), Mumbai-400098, India,

About: Paul Joseph Wiita

Department of Physics, The College of New Jersey, Ewing, NJ 08628-0718, USA