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Proceeding Paper

Study of Periodic Signals from Blazars †

Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland
Presented at the Recent Progress in Relativistic Astrophysics, Shanghai, China, 6–8 May 2019.
Proceedings 2019, 17(1), 15;
Published: 10 December 2019
(This article belongs to the Proceedings of Recent Progress in Relativistic Astrophysics)


The search for periodic signals from blazars has become an actively pursued field of research in recent years. This is because periodic signals bring us information about the processes occurring near the innermost regions of blazars, which are mostly inaccessible to our direct view. Such signals provide insights into some of the extreme conditions that take place in the vicinity of supermassive black holes that lead to the launch of the relativistic jets. In addition, studies of characteristic timescales in blazar light curves shed light on some of the challenging issues in blazar physics that include disk-jet connection, strong gravity near fast-rotating supermassive black holes and release of gravitational waves from binary supermassive black hole systems. However, a number of issues associated with the search for quasi-periodic oscillations (QPOs) in blazars e.g., red-noise dominance, modest significance of the detection, periodic modulation lasting for only a couple of cycles and their transient nature, make it difficult to estimate the true significance of the detection. Consequently, it also becomes difficult to make meaningful inferences about the nature of the on-going processes. In this proceedings, results of study focused on searching for QPOs in a number of blazar multi-frequency light curves are summarized. The time series analyses of long term observations of the blazars revealed the presence of year-timescale QPOs in the sources including OJ 287 (optical), Mrk 501 (gamma-ray), J1043+2408 (radio) and PKS 0219-164 (radio). A likely explanations, we discuss a number of scenarios including binary supermassive black hole systems, lense-thirring precession, and jet precession.
Keywords: supermassive black holes: non-thermal radiation; active galactic nuclei: BL Lacertae objects; galaxies: jets; method: time series analysis supermassive black holes: non-thermal radiation; active galactic nuclei: BL Lacertae objects; galaxies: jets; method: time series analysis

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MDPI and ACS Style

Bhatta, G. Study of Periodic Signals from Blazars. Proceedings 2019, 17, 15.

AMA Style

Bhatta G. Study of Periodic Signals from Blazars. Proceedings. 2019; 17(1):15.

Chicago/Turabian Style

Bhatta, Gopal. 2019. "Study of Periodic Signals from Blazars" Proceedings 17, no. 1: 15.

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