A γ-ray Quasi-periodic Modulation in the Blazar PKS 0301–243?

Zhang, Peng-Fei; Yan, Dahai; Zhou, Jianeng; Fan, Yi‐Zhong; Wang, Jiancheng; Zhang, Li

doi:10.3847/1538-4357/aa7ecd

Cited by 47 publications

(25 citation statements)

References 49 publications

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“…at γ-ray energies this has been possible only with the advent of the Fermi-LAT in 2008 thanks to the continuous and systematic sky monitoring in the MeV-GeV energy range. A similar approximately two-year quasi-periodicity (with significance above > 3σ) has also been claimed in a few other blazars such as PKS 0537-441(Sandrinelli et al 2016), BL Lacertae(Sandrinelli et al 2017), PKS 2155-304(Zhang et al 2017a), PKS 0301-243(Zhang et al 2017b), and J1043+2408(Bhatta 2018).…”

supporting

confidence: 76%

A parsec-scale wobbling jet in the high-synchrotron peaked blazar PG 1553+113

Lico

Liu

Giroletti

et al. 2020

A&A

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Context. The detection of quasi-periodic variability in active galactic nuclei (AGNs) in general, and in blazars in particular, is key to our understanding of the origin and nature of these objects as well as their cosmological evolution. PG 1553+113 is the first blazar showing an approximately two-year quasi-periodic pattern in its γ-ray light curve, which is also revealed at optical frequencies.Aims. Such quasi-periodicity might have a geometrical origin, possibly related to the precessing nature of the jet, or could be intrinsic to the source and related to pulsational accretion flow instabilities. In this work we investigate and characterise the high-resolution radio emission properties of PG 1553+113 on parsec scales in order to differentiate between these different physical scenarios. Methods. We monitored the source with the very long baseline array (VLBA) at 15, 24, and 43 GHz during an entire cycle of γ-ray activity in the period 2015-2017, with a cadence of about 2 months, both in total and polarised intensity. We constrained the jet position angle across the different observing epochs by investigating the total intensity ridge lines. Results. We find a core-dominated source with a limb-brightened jet structure extending for ∼ 1.5 mas in the northeast direction whose position angle varies in time in the range ∼ 40 • − 60 • . No clear periodic pattern can be recognized in the VLBA light curves during 2015-2017 or in the 15 GHz Owens Valley Radio Observatory light curve during the period 2008-2018. The core region polarisation percentage varies in the range ∼ 1 − 4%, and the polarisation angle varies from being roughly parallel to roughly transverse to the jet axis. We estimate a rotation measure value in the core region of ∼ −1.0 ± 0.4 × 10 4 rad m −2 . The brightness temperature (T B ) is found to decrease as the frequency increases with an intrinsic value of ∼ 1.5 × 10 10 K and the estimated Doppler factor is ∼ 1.4. Conclusions. Although the jet wobbling motion indicates that geometrical effects can produce an enhanced emission through the Doppler boosting modulation, additional mechanisms are required in order to account for the quasi-periodic variability patterns observed in γ rays. The intrinsic T B value indicates that the total energy in the core region is dominated by the magnetic field.

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confidence: 76%

A parsec-scale wobbling jet in the high-synchrotron peaked blazar PG 1553+113

Lico

Liu

Giroletti

et al. 2020

A&A

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“…At γ-rays, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope (Fermi) has provided a powerful tool for monitoring blazars at γ-ray energies 10 . Candidate γ-ray QPOs have been discovered; [11][12][13][14][15][16][17][18] these QPOs all have yearly time scales. Here 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 1997 19,20 , but fewer cycles were observed then and the strength of that oscillatory signal is weak.…”

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confidence: 99%

A 34.5 day quasi-periodic oscillation in γ-ray emission from the blazar PKS 2247–131

et al. 2018

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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.

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“…In the case of AGNs with weak jets, the observed QPOs can be explained by a variety of theoretical models such as instabilities in the AD [63], hot spots in the AD [27] or the disk precision [64]. Alternatively, the AGNs with strong jets such as blazars, the observed QPO in all likelihood is dominated by processes related to the jet itself, such as the precession of the jet (e.g., [65][66][67] and references therein) or to the processes that feed the jet such as pulsational accretion flow instabilities [20].…”

Section: Discussionmentioning

confidence: 99%

“…The prevailing notion that AGNs show that only random flux variations over a range of time scales from low energy radio to high energy γ-ray bands have been challenged since the last decade, with the first detection of a highly significant quasi-periodic oscillation (QPO) of about 1 h in the X-ray light curve of the narrow-line Seyfert 1 (NLSy1) galaxy RE J1034+396 [11,12]. Since then, QPOs in AGNs have been detected in the radio ( [13][14][15] and references therein), optical ( [16,17] and references therein), X-rays [11,18,19] and γrays ( [20] and references therein). Thus, it is now evident that AGNs do show QPO similar to what is seen in galactic compact X-ray sources that include white dwarfs, neutron stars, and X-ray binaries (XRBs) [21].…”

Section: Introductionmentioning

confidence: 99%

A Possible Quasi-Periodic Oscillation in the X-ray Emission of 3C 120

et al. 2021

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We present here the detection of a possible quasi-periodic oscillation (QPO) signal in the X-ray light curve of the active galactic nucleus 3C 120, a broad line radio galaxy at z = 0.033. The hint of a QPO at the 3σ level at 7.1 × 10−6 Hz (∼1.65 days) was detected based on the analysis of X-ray data acquired in the 3–79 keV band by the Nuclear Spectroscopic Telescope Array (NuSTAR). The data, when processed separately in the soft (3–10 keV), hard (10–79 keV) and the total (3–79 keV) bands using four different techniques, namely discrete correlation function, Lomb Scargle periodogram, structure–function, and power spectral density indicated the presence of a QPO. 3C 120 very well fits in the negative correlation in the frequency of the QPO versus the black hole mass (FQPO versus MBH) diagram known for stellar-mass and supermassive black hole sources. Considering the observed signs of QPO to represent the innermost stable orbit of the accretion disk, we found a black hole mass of 1.9×109 M⊙ for a Kerr black hole and 3.04×108 M⊙ for a Schwarzschild black hole. This deduced black hole mass from QPO measurement is a few times larger than the black hole mass obtained from reverberation mapping observations.

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A γ-ray Quasi-periodic Modulation in the Blazar PKS 0301–243?

Cited by 47 publications

References 49 publications

A parsec-scale wobbling jet in the high-synchrotron peaked blazar PG 1553+113

A parsec-scale wobbling jet in the high-synchrotron peaked blazar PG 1553+113

A 34.5 day quasi-periodic oscillation in γ-ray emission from the blazar PKS 2247–131

A Possible Quasi-Periodic Oscillation in the X-ray Emission of 3C 120

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