Optical Variability Modeling of Newly Identified Blazar Candidates behind Magellanic Clouds

Żywucka, N.; Tarnopolski, Mariusz; Böttcher, M.; Stawarz, Ł.; Marchenko, Volodymyr

doi:10.3847/1538-4357/ab5fe5

Cited by 13 publications

(12 citation statements)

References 117 publications

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“…Finally, given all the above considerations, the A − T plane, while potentially useful in classifying LCs (cf. Żywucka et al 2020;Tarnopolski et al 2020), does not hint at any clustering of long GRBs into more than one group (other than an overconcentration of flat PSDs at (1, 2 /3), likely owing to low signal-to-noise ratio), consistent with the findings of Jespersen et al (2020).…”

Section: The a − T Planesupporting

confidence: 70%

“…The already proposed generation mechanisms (MRI (Masada et al 2007); precessing magnetic field (Ziaeepour & Gardner 2011)) can be complemented with some models employed for active galactic nuclei (AGNs), since both GRBs and AGNs often exhibit striking similarities (Wang et al 2014;Wu et al 2016;Deng et al 2016). In the simplest scenario, association of the break time scale with the viscous time scale of an accretion disk, coupled with the Keplerian motion on a circular orbit around the newly forming BH (Mohan & Mangalam 2014;Żywucka et al 2020) can explain the PSD breaks in GRBs as well. Since a relativistic two-body problem (in both Schwarzschild and Kerr metrics) allows for an inspiral (which is impossible in the Newtonian framework), occuring in a finite time (Levin & Perez-Giz 2008), a fragmented accretion disk could result in QPOs, lasting several cycles, and possibly chirping signals as well.…”

Section: Qposmentioning

confidence: 99%

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A Comprehensive Power Spectral Density Analysis of Astronomical Time Series. II. The Swift/BAT Long Gamma-Ray Bursts

Tarnopolski,

Marchenko

2021

Preprint

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We investigated the prompt light curves (LCs) of long gamma-ray bursts (GRBs) from the Swift/BAT catalog. We aimed to characterize their power spectral densities (PSDs), search for quasiperiodic oscillations (QPOs), and conduct novel analyses directly in the time domain. We analyzed the PSDs using Lomb-Scargle periodograms, and searched for QPOs using wavelet scalograms. We also attempted to classify the GRBs using the Hurst exponent, H, and the A − T plane. The PSDs fall into three categories: power law (PL; P (f ) ∝ 1/f β ) with index β ∈ (0, 2), PL with a non-negligible Poisson noise level (PLC) with β ∈ (1, 3), and a smoothly broken PL (SBPL; with Poisson noise level) yielding high-frequency index β 2 ∈ (2, 6). The latter yields break time scales on the order of 1-100 seconds. The PL and PLC models are broadly consistent with a fully developed turbulence, β = 5 /3. For an overwhelming majority of GRBs (93%), H > 0.5, implying ubiquity of the long-term memory. We find no convincing substructure in the A − T plane. Finally, we report on 34 new QPOs: with one or more constant leading periods, as well as several chirping signals. The presence of breaks and QPOs suggests the existence of characteristic time scales that in at least some GRBs might be related to the dynamical properties of plasma trajectories in the accretion disks powering the relativistic jets.

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Section: The a − T Planesupporting

confidence: 70%

Section: Qposmentioning

confidence: 99%

A Comprehensive Power Spectral Density Analysis of Astronomical Time Series. II. The Swift/BAT Long Gamma-Ray Bursts

Tarnopolski,

Marchenko

2021

Preprint

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“…Whether the stochastic process remains stationery on the timescales probed is crucial for understanding the physical processes operating on widely different spatial scales (e.g., Kushwaha et al 2016;Giebels & Degrange 2009). Studies of different blazars performed at different wavelengths have indeed revealed breaks in the slopes of PSDs, which could be attributed to the size of the emission zone or, alternatively, to cooling timescales of the particles (e.g., Abramowski et al 2010;Sobolewska et al 2014;Isobe et al 2015;Kastendieck et al 2011;Abdalla et al 2017;Ryan et al 2019;Żywucka et al 2020). The emerging picture of the broad-band blazar variability is that at higher energies (i.e., X−ray, and GeV and TeV γ−rays) is characterized by flicker/pink-noise processes (i.e., Abdalla et al 2017;Abdo et al 2010;Isobe et al 2015), whereas at lower energies (GHz band radio and optical frequencies) damped/red-noise type processes dominate (i.e., Ciprini et al 2007;Kastendieck et al 2011;Park & Trippe 2014;Max-Moerbeck et al 2014b;Nilsson et al 2018).…”

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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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“…The FSRQs are characterised by lower values of A than BL Lacs and these two classes of blazars are clearly separated on the A − T plane (Figure 3). This was earlier discovered by [13]…”

Section: Resultsmentioning

confidence: 70%

Comprehensive power spectral density analysis of the Fermi-LAT $γ$-ray light curves of selected blazars

Żywucka¹,

Tarnopolski²,

Marchenko³

et al. 2021

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We present the results of the Fermi-Large Area Telescope (LAT) light curve (LC) modelling of selected blazars: six flat spectrum radio quasars (FSRQs) and five BL Lacertae (BL Lacs). All objects have densely sampled and long-term LCs, over 10 years. For each blazar we generated three LCs with 7, 10, and 14 days binning, using the latest LAT 8-year source catalog and binned analysis provided within the package. The LCs were modelled with several tools: the Fourier transform, the Lomb-Scargle periodogram (LSP), the autoregressive moving average (ARMA), the fractional autoregressive integrated moving average, the continuous-time autoregressive moving average (CARMA) processes, the Hurst exponents (𝐻), the A − T plane, and the wavelet scalogram. The power law indices 𝛽 calculated from the Fourier and LSP modelling are consistent with each other. Many objects yield 𝛽 1, with PKS 2155-304 even flatter, but some are significantly steeper, e.g. Mrk 501 and B2 1520+31. The power law PSD is indicative of a self-affine stochastic process characterised by 𝐻, underlying the observed variability. Several algorithms for the 𝐻 estimations are employed. For some objects we found 𝐻 > 0.5, indicating long-term memory. We confirm a quasi-periodic oscillation (QPO) in the PKS 2155−304 data with the period of 612 ± 42 days at a 3𝜎 significance level, but do not detect any QPOs in other objects. The ARMA results give in general higher orders for 7 days binned LCs and lower orders for 10 and 14 days binned LCs, implying temporal variations in the LCs are consistently captured by the fitted models. CARMA modelling leads to featureless PSDs. The recently introduced A − T plane allows us to successfully classify the PSDs based on the LCs alone and clearly separates the FSRQ and BL Lac types of blazars.

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Optical Variability Modeling of Newly Identified Blazar Candidates behind Magellanic Clouds

Cited by 13 publications

References 117 publications

A Comprehensive Power Spectral Density Analysis of Astronomical Time Series. II. The Swift/BAT Long Gamma-Ray Bursts

A Comprehensive Power Spectral Density Analysis of Astronomical Time Series. II. The Swift/BAT Long Gamma-Ray Bursts

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

Comprehensive power spectral density analysis of the Fermi-LAT $γ$-ray light curves of selected blazars

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