Abstract
Since 2016 October, the active galaxy PKS 2247−131 has undergone a γ-ray outburst, which we studied using data obtained with the Fermi Gamma-ray Space Telescope. The emission arises from a relativistic jet in PKS 2247−131, as an optical spectrum only shows a few weak absorption lines, typical of the BL Lacertae sub-class of the blazar class of active galactic nuclei. Here we report a ≃34.5 day quasi-periodic oscillation (QPO) in the emission after the initial flux peak of the outburst. Compared to one-year time-scale QPOs, previously identified in blazars in Fermi energies, PKS 2247−131 exhibits the first clear case of a relatively short, month-like oscillation. We show that this QPO can be explained in terms of a helical structure in the jet, where the viewing angle to the dominant emission region in the jet undergoes periodic changes. The time scale of the QPO suggests the presence of binary supermassive black holes in PKS 2247−131.
Highlights
Since 2016 October, the active galaxy PKS 2247−131 has undergone a γ-ray outburst, which we studied using data obtained with the Fermi Gamma-ray Space Telescope
We report our discovery of a possible month-long quasi-periodic oscillation (QPO) in γ-ray emission of the blazar PKS 2247−131; the only previous claim of a QPO on this time-scale was reported to have been detected at γ-ray TeV energies during a flare of the blazar Markarian 501 in 199719,20, but fewer cycles were observed and the strength of that oscillatory signal is weak
In 2016 October, a γ-ray outburst event in the direction of PKS 2247−131 was detected with Fermi LAT21, and based on multi-wavelength observations, we confirmed the outburst to have originated from PKS 2247 −131
Summary
Since 2016 October, the active galaxy PKS 2247−131 has undergone a γ-ray outburst, which we studied using data obtained with the Fermi Gamma-ray Space Telescope. Compared to one-year time-scale QPOs, previously identified in blazars in Fermi energies, PKS 2247−131 exhibits the first clear case of a relatively short, month-like oscillation. We show that this QPO can be explained in terms of a helical structure in the jet, where the viewing angle to the dominant emission region in the jet undergoes periodic changes. The SMBH is sometimes fed by enough matter, accreted through a surrounding disc, to produce strong emissions from the central region of the galaxy that can sometimes outshine the emission from all the stars in the galaxy These Active Galactic Nuclei (AGN)[2] naturally are objects of great interest, and relativistic jets, launched from the immediate vicinity of the SMBHs, are found to be associated with ~10% of AGN3. We report our discovery of a possible month-long QPO in γ-ray emission of the blazar PKS 2247−131; the only previous claim of a QPO on this time-scale was reported to have been detected at γ-ray TeV energies during a flare of the blazar Markarian 501 in 199719,20, but fewer cycles were observed and the strength of that oscillatory signal is weak
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