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      Permanent link:
      https://www.ias.ac.in/article/fulltext/joaa/039/06/0065

    • Keywords

       

      Active galaxies; Seyferts; variability.

    • Abstract

       

      Flux variability is one of the defining characteristics of Seyfert galaxies, a class of active galactic nuclei (AGN). Although these variations are observed over a wide range of wavelengths, results on their flux variability characteristics in the ultraviolet (UV) band are very limited.We present here the long-term UV fluxvariability characteristics of a sample of fourteen Seyfert galaxies using data from the International Ultraviolet Explorer acquired between 1978 and 1995. We found that all the sources showed flux variations with no statistically significant differences in the amplitude of UV flux variation between shorter and longer wavelengths. Also, the flux variations between different near-UV (NUV, 1850−3300 å) and far-UV (FUV, 1150−2000 å) pass bands in the rest frames of the objects are correlated with no time lag. The data show indications of (i) a mild negative correlation of UV variability with bolometric luminosity and (ii) weak positive correlation between UV variability and black hole mass. At FUV, about 50% of the sources show a strong correlation between spectral indices and flux variations with a hardening when brightening behaviour, while for the remaining sources the correlation is moderate. In NUV, the sources do show a harder spectrum when brighter, but the correlation is either weak or moderate.

    • Author Affiliations

       

      N. SUKANYA1 C. S. STALIN2 P. JOSEPH2 S. RAKSHIT2 3 D. PRAVEEN4 R. DAMLE1

      1. Department of Physics, Bangalore University, Bengaluru 560 056, India.
      2. Indian Institute of Astrophysics, Block II, Koramangala, Bengaluru 560 034, India.
      3. Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea.
      4. Physics Department, Amrita School of Engineering, Bengaluru 560 035, India.
    • Dates

       
  • Journal of Astrophysics and Astronomy | News

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      Posted on January 27, 2016

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