• Fulltext

       

        Click here to view fulltext PDF


      Permanent link:
      https://www.ias.ac.in/article/fulltext/joaa/025/01-02/0001-0055

    • Keywords

       

      Galaxies: active; galaxies: jets; galaxies: photometry; quasars: general

    • Abstract

       

      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 rangez ≃ 0.2 toz ≃ 2.2. The sample, matched in the optical luminosity—redshift(MB—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).

    • Author Affiliations

       

      C. S. Stalin1 2 3 Gopal-Krishna2 Ram Sagar1 Paul J. Wiita4

      1. Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital - 263 129, India
      2. National Centre for Radio Astrophysics, TIFR, Pune University Campus, Pune - 411 007, India
      3. Laboratoire de Physique Corpusculaire et Cosmolgie, College de France, 11 pl. Marcelin Berthelot, Paris Cedex 5 - F-75231, France
      4. Department of Physics & Astronomy, MSC 8R0314, Georgia State University, Atlanta, Georgia - 30303-3088, USA
    • Dates

       
  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.