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      Permanent link:
      https://www.ias.ac.in/article/fulltext/joaa/032/01-02/0109-0112

    • Keywords

       

      Galaxies: active; galaxies: evolution; BL Lac objects: general.

    • Abstract

       

      Many quasi-simultaneous optical observations of nine BL Lac objects are obtained from literature. We study the relationship between the optical spectral index and the luminosity of BL Lac objects, and are tempted to exploit spectral evolution in the optical frequency ranges. Our results show that:

      1. The optical spectra index of the low-frequency peaked BL Lac objects (LBLs) is steeper than the high-frequency peaked BL Lac objects (HBLs);

      2. The spectra tend to be softer when the source becomes brighter for LBLs and the intermediate BL Lac objects (IBLs) (i.e., bluer-when-brighter), and the spectra of HBLs does not vary when the brightness of HBLs changes. Possible explanations are briefly discussed for this phenomenon.

    • Author Affiliations

       

      X. W. Bi1 B. Z. Wang2 Z. Q. Ni3 Q. Cai1 J. J. Tian1

      1. Department of Physics, Honghe University, Mengzi 661100, Yunnan, China.
      2. Department of Physics and Electronic Engineering, Jiaozuo Teachers College, Jiaozuo 454000, Henan, China.
      3. Nationality Middle School of Shilin, Shilin 651000, Yunnan, China.

    • Dates

       
      Published
      6 March 2011

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      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.

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