Bhattacharya, Debbijoy and Mohana A, Krishna and Gulati, Sanna and Bhattacharyya, Subir and Bhatt, Nilay and Sreekumar, Parameswaran and Stalin, C S (2017) Unusual long-term low activity states of EGRET Blazars in the Fermi Era. Monthly Notices of the Royal Astronomical Society, 471 (4). pp. 5008-5017. ISSN 1745-3933

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Abstract

We examine the long-term (∼ 10 years) γ-ray variability of blazars observed by EGRET and Fermi and find that 10 EGRET-detected flat spectrum radio quasars (FSRQs) were not present in any of the Fermi catalogue (during the first four years of Fermi observation). Six of these 10 EGRET sources show possible Fermi counterparts based on overlap with error circles given in 3 r d Fermi catalogue. A seventh EGRET source is positionally consistent with a newly discovered Fermi source from our analysis. Unlike the high luminosity state exhibited during 1991 to 1995, our analysis using seven years of Fermi data showed that five of these are at its low luminosity state in the GeV band. This result indicates that FSRQs exhibit a long-term quiescent state (more than 7 years). In addition, 37 new γ-ray sources are also detected during the course of this analysis. On the basis of AGN being the most dominant source class in γ-rays, many of these new sources could be associated with AGN and may exhibit long-term variabilities in γ-rays.

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