Gamma-ray and optical oscillations of 0716+714, MRK 421, and BL Lacertae

Sandrinelli, A.; Covino, S.; Treves, A.; Lindfors, E.; Raiteri, C. M.; Nilsson, K.; Takalo, L. O.; Reinthal, R.; Berdyugin, A.; Ramazani, Vandad Fallah; Kadenius, V.; Tuominen, T.; Kehusmaa, P.; Bachev, R.; Strigachev, A.

doi:10.1051/0004-6361/201630288

Cited by 64 publications

(76 citation statements)

References 61 publications

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“…No this energy range, similar to the radio-UV and GeV-TeV ranges. Periodic brightness variations have not been found also by different authors (see, e.g., Carnerero et al 2017;Sandrinelli et al 2017).…”

Section: Variability Charactermentioning

confidence: 79%

Swift Observations of Mrk 421 in Selected Epochs. III. Extreme X-Ray Timing/Spectral Properties and Multiwavelength Lognormality during 2015 December–2018 April

Kapanadze

Gurchumelia

Dorner

et al. 2020

ApJS

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We present the results from the timing and spectral study of Mrk 421 based mainly on the Swift data in the X-ray energy range obtained during the time interval 2015 December-2018 April. The most extreme X-ray flaring activity on the long-term, daily and intraday timescales was observed during the 2-month period which started in 2017 December when the 0.3-10 keV flux exceeded a level of 5×10 −9 erg cm −2 s −1 , recorded only twice previously. While the TeV-band and X-ray variabilities mostly were correlated, the source often varied in a complex manner in the MeV-GeV and radio-UV energy ranges, indicating that the multifrequency emission of Mrk 421 could not be always generated in a single zone. The longer-term flares at X-rays and γ-rays showed a lognormal character, possibly indicating a variability imprint of the accretion disk onto the jet. A vast majority of the 0.3-10 keV spectra were consistent with the log-parabolic model, showing relatively low spectral curvature and correlations between the different spectral parameters, predicted in the case of the first and secondorder Fermi processes. The position of the synchrotron spectral energy distribution (SED) peak showed an extreme variability on diverse timescales between the energies E p <0.1 keV and E p >15 keV, with 15% of the spectra peaking at hard X-rays and was related to the peak height as S p ∝E α p with α∼0.6, which is expected for the transition from Kraichnan-type turbulence into the "hard-sphere" one. The 0.3-300 GeV spectra showed the features of the hadronic contribution, jet-star interaction and upscatter in the Klein-Nishina regime in different time intervals.

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Section: Variability Charactermentioning

confidence: 79%

Swift Observations of Mrk 421 in Selected Epochs. III. Extreme X-Ray Timing/Spectral Properties and Multiwavelength Lognormality during 2015 December–2018 April

Kapanadze

Gurchumelia

Dorner

et al. 2020

ApJS

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“…Possible γ-ray QPOs have been reported for several blazars (e.g., Sandrinelli et al 2014;Ackermann et al 2015;Sandrinelli et al 2016aSandrinelli et al , 2016bSandrinelli et al , 2017Zhang et al 2017aZhang et al , 2017b. However, the significance of the claimed QPOs is not very high.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…So far, the Large Area Telescope (LAT; Atwood et al 2009) on board Fermi has collected gamma-rays for over 8 years. The possible quasiperiodic variabilities of blazars with periods of ∼2-3 yr have been reported in γ-ray fluxes of several blazars (e.g., Sandrinelli et al 2014;Ackermann et al 2015;Sandrinelli et al 2016aSandrinelli et al , 2016bSandrinelli et al , 2017Zhang et al 2017aZhang et al , 2017b. In particular, PKS 2155-304 has been reported to have a significance of ∼4σ (Zhang et al 2017b).…”

Section: Introductionmentioning

confidence: 92%

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

Zhang

Yan

Zhou

et al. 2017

ApJ

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We report a nominally high-confidence γ-ray quasi-periodic modulation in the blazar PKS 0301-243. For this target, we analyze its Fermi-LAT Pass 8 data from 2008 August to 2017 May. Two techniques, i.e., maximum likelihood optimization and exposure-weighted aperture photometry, are used to build the γ-ray light curves. Then, both the Lomb-Scargle periodogram and the weighted wavelet Z-transform are applied to the light curves to search for period signals. A quasi-periodicity with a period of 2.1±0.3 yr appears at the significance level of s5 , although it should be noted that this putative quasi-period variability is seen in a data set that is barely four times longer. We speculate that this γ-ray quasi-periodic modulation may be evidence of a binary supermassive black hole.

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“…Mrk 421 has been a subject of intense monitoring ever since its discovery in the VHE band, in particular, the relation between the variations at X-ray and VHE γ−rays have been probed widely (B lażejowski et al 2005;Fossati et al 2008;Hovatta et al 2015;Ahnen et al 2016;González et al 2019). For the blazar Mrk 421, no quasi-periodic oscillations (QPOs) in the decade-long optical and HE γ−ray light curves were reported in the study of Sandrinelli et al (2017) ; 2004-2012), partial HE γ−ray (Fermi-LAT; and X−ray (Swift-XRT;2006 light curves have been presented in Abdalla et al (2017) and Kapanadze et al (2014). PKS 2155−304 is also known for a log-normal distribution of TeV flux densities, and also for a change in the PSD slope, such that β ∼ 1 and ∼ 2 on timescales longer and shorter than 1 day, respectively).…”

Section: Introductionmentioning

confidence: 99%

Blazar variability power spectra from radio up to TeV photon energies: Mrk 421 and PKS 2155−304

Goyal

2020

Monthly Notices of the Royal Astronomical Society

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We present the results of the power spectral density (PSD) analysis for the blazars Mrk 421 and PKS 2155−304, using good-quality, densely sampled light curves at multiple frequencies, covering 17 decades of the electromagnetic spectrum, and variability timescales from weeks up to a decade. The data were collected from publicly available archives of observatories at radio from OVRO, optical and infrared (B, V, R, I, J, H, and K-bands), X-rays from the Swift and the Rossi X-ray Timing Explorer, high and very high energy γ−rays from the Fermi and Very Energetic Radiation Imaging Telescope Array System as well as the High Energy Stereoscopic System. Our results are: (1) the power-law form of the variability power spectra at radio, infra-red and optical frequencies have slopes ∼1.8, indicative of random-walk type noise processes;(2) the power-law form of the variability power spectra at higher frequencies, from Xrays to very high energy γ-rays, however, have slopes ∼1.2, suggesting a flicker noise type process; (3) there is significantly more variability power at X-rays, high and very high energy γ-rays on timescales 100 days, as compared to lower energies. Our results do not easily fit into a simple model, in which a single compact emission zone is dominating the radiative output of the blazars across all the timescales probed in our analysis. Instead, we argue that the frequency-dependent shape of the variability power spectra points out a more complex picture, with highly inhomogeneous outflow producing non-thermal emission over an extended, stratified volume.

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Gamma-ray and optical oscillations of 0716+714, MRK 421, and BL Lacertae

Cited by 64 publications

References 61 publications

Swift Observations of Mrk 421 in Selected Epochs. III. Extreme X-Ray Timing/Spectral Properties and Multiwavelength Lognormality during 2015 December–2018 April

Swift Observations of Mrk 421 in Selected Epochs. III. Extreme X-Ray Timing/Spectral Properties and Multiwavelength Lognormality during 2015 December–2018 April

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

Blazar variability power spectra from radio up to TeV photon energies: Mrk 421 and PKS 2155−304

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