Optical variability properties of high luminosity AGN classes

Stalin, C. S. ; Gopal-Krishna, ; Ram Sagar, ; Wiita, Paul J. (2004) Optical variability properties of high luminosity AGN classes Journal of Astrophysics and Astronomy, 25 (1-2). pp. 1-55. ISSN 0250-6335

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Official URL: http://www.ias.ac.in/jaa/marjune2004/absmarjun.htm...

Related URL: http://dx.doi.org/10.1007/BF02702287


We present the results of a comparative study of the intranight optical variability (INOV) characteristics of radio-loud and radioquiet quasars, which involves a systematic intra-night optical monitoring of seven sets of high luminosity AGNs covering the redshift range z ⋍ 0.2 to z ⋍ 2.2. The sample, matched in the optical luminosity-redshift(M B-z) plane, consists of seven radio-quiet quasars (RQQs), eight radio lobedominated quasars (LDQs), five radio core-dominated quasars (CDQs) and six BL Lac objects (BLs). Systematic CCD observations, aided by a careful data analysis procedure, have allowed us to detect INOV with amplitudes as low as about 1%. Present observations cover a total of 113 nights (720 hours) with only a single quasar monitored as continuously as possible on a given night. Considering the cases of only unambiguous detections of INOV we have estimated duty cycles (DCs) of 17%, 12%, 20% and 61% for RQQs, LDQs, CDQs, and BLs, respectively. The much lower amplitude and DC of ESfOV shown by RQQs compared to BLs may be understood in terms of their having optical synchrotron jets which are modestly misdirected from us. From our fairly extensive dataset, no general trend of a correlation between the INOV amplitude and the apparent optical brightness of the quasar is noticed. This suggests that the physical mechanisms of INOV and long term optical variability (LTOV) do not have a one-to-one relationship and different factors are involved. Also, the absence of a clear negative correlation between the INOV and LTOV characteristics of blazars of our sample points toward an inconspicuous contribution of accretion disk fluctuations to the observed INOV. The INOV duty cycle of the AGNs observed in this program suggests that INOV is associated predominantly with the highly polarized optical emission components. We also report new VLA imaging of two RQQs (1029 + 329 & 1252 + 020) in our sample which has yielded a 5 GHz detection in one of them (1252 + 020; S5GHZ ⋍ 1 mJy).

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Galaxies: Active; Galaxies: Jets; Galaxies: Photometry; Quasars: General
ID Code:65282
Deposited On:17 Oct 2011 03:43
Last Modified:18 May 2016 13:21

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