The long-term multiwavelength observations of the blazar PKS 2005-489

Kapanadze, Bidzina

doi:10.1016/j.astropartphys.2021.102620

Cited by 4 publications

(3 citation statements)

References 67 publications

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“…3 (U band versus the X-ray band). Our variability results for PKS2005-489, Mrk 421, and 3C 454.3 agree with those of the recent literature that have utilized the same data from Swift(Raiteri et al 2011;Aleksić et al 2015;Kapanadze 2021). The overall anticorrelation between the X-ray and UV/optical fluxes, and power-law spectral densities present in the nonflaring states of Mrk 421 are especially evident, along with the prominent X-ray variability (which follows the UV/optical) of 3C 454.3.The average range in normalized flux units across all 19 sources is 1.94 for the X-ray band and 0.99 for the UV/optical band, with the best observed objects illustrating the largest ranges in both fluxes (without outliers).…”

supporting

confidence: 91%

“…The launch of the Fermi Gamma-ray Space Telescope, a few years after Swift, made it easier to obtain observations in both the X-ray and gamma-ray regions. This led to a number of extensive investigations of variability from the radio through the gamma-ray region for individual objects, and on a broad range of timescales, such as for 3C-454.3, OJ 287, PKS 0735+178, PKS 2155-304, PKS 2004, and S5 0716+714, to mention a few (Raiteri et al 2011;Aleksić et al 2015;Ahnen et al 2017;Goyal et al 2017Goyal et al , 2018Kapanadze et al 2017;MAGIC Collaboration et al 2018;Chevalier et al 2019;Kapanadze 2021). For a sample of radiobright blazars, we apply a uniform set of tests to characterize the variability, using structure functions to explore these properties.…”

Section: Introductionmentioning

confidence: 99%

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Characterizing the Variable X-Ray and UV–Optical Flux Behavior of Blazars

Moo

Bregman

Reynolds

2022

ApJ

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The variability of blazars in the X-ray and optical regions both informs the physics of their emitting region and places demands on the observer if a program requires that the object be bright or faint. The extensive simultaneous X-ray and optical observation by the Neil Gehrels Swift Observatory (Swift) provides the best insight into the variable nature of these objects. This program uses Swift data for 19 X-ray-bright blazars, generally at z > 0.1, to determine their variability properties. The analysis is based on structure functions and provides insight into the nature of the variability and how it depends on time, luminosity, and redshift. We also consider strategies for observing blazars at or above average brightness, given a time delay between planning an observation and obtaining the data. This is critical to observations with orbiting X-ray telescopes, current or future. The variability in the soft X-ray band is typically three to eight times larger than at UV–optical wavelengths, at fixed time differences (i.e., 30 or 100 days). There is almost no difference in the amplitude of variation (X-ray or UV–optical) as a function of redshift (time delay of 30 days) and a modest positive correlation with luminosity. In the X-ray band, blazars that become brighter than normal typically remain bright for at least 2–3 months, although with significant flickering. One can avoid observing objects that are significantly below the average X-ray flux by scheduling the observation when F X > 0.9F X,avg, which requires monitoring observations near the time of the scheduling activity.

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supporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Characterizing the Variable X-Ray and UV–Optical Flux Behavior of Blazars

Moo

Bregman

Reynolds

2022

ApJ

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“…The lognormal γ-ray variability has been reported for a number of HBLs. Namely, this was the case for the observations performed with LAT (Mrk 421 [44,206,207]), Mrk 501 ( [208]), 1ES 0033+595 ( [187]), PKS 2005−489 ( [209], RGB 0136+391 ( [210]), H1722+119 ([210] etc.) and Cherenkov-type telescopes (Mrk 421 [44,207], Mrk 501 [134,208] and PKS 2155−304 ( [134]).…”

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confidence: 97%

Gamma-ray Emission and Variability Processes in High-Energy-Peaked BL Lacertae Objects

Kapanadze

2023

Universe

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BL Lac objects are active galactic nuclei notable for a beamed nonthermal radiation, which is generated in one of the relativistic jets forming a small angle to the observer’s line-of-sight. The broadband spectra of BL Lacs show a two-component spectral energy distribution (SED). High-energy-peaked BL Lacs (HBLs) exhibit their lower-energy (synchrotron) peaks at UV to X-ray frequencies. The origin of the higher-energy SED component, representing the γ-ray range in HBLs, is still controversial and different emission scenarios (one- and multi-zone synchrotron self-Compton, hadronic etc.) are proposed. In γ-rays, HBLs show a complex flaring behavior with rapid and large-amplitude TeV-band variations on timescales down to a few minutes. This review presents a detailed characterization of the hypothetical emission mechanisms which could contribute to the γ-ray emission, their application to the nearby TeV-detected HBLs, successes in the broadband SED modeling and difficulties in the interpretation of the observational data. I also overview the unstable processes to be responsible for the observed γ-ray variability and particle energization up to millions of Lorentz factors (relativistic shocks, magnetic reconnection, turbulence and jet-star interaction). Finally, the future prospects for solving the persisting problems by means of the dedicated gamma-ray observations and sophisticated simulations are also addressed.

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Optical monitoring in southern blazars. Analysis of variability and spectral colour behaviours

Zibecchi,

Andruchow,

Marchesini

et al. 2024

Monthly Notices of the Royal Astronomical Society

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We present the results of the optical monitoring of 18 southern blazars in the V and R Johnson-Cousins bands. Our main objective is to study the variations in the optical flux and their relationship with the colour and spectral variabilities. The optical observations were acquired with the 2.15 m ‘Jorge Sahade’ telescope, CASLEO, Argentina. The whole campaign comprised from 2014 April to 2019 September. In addition, X-ray data were taken from the Chandra X-ray Observatory and the Swift/XRT databases, and γ-ray data was taken from the Fermi-LAT 3FGL catalogue. From the total of 18 blazars, we found variability in each one of the timescales considered for 6 blazars (PKS 0208-512, PKS 1116-46, PKS 1440-389, PKS 1510-089, PKS 2005-489 and PKS 2155-304). In particular, from the colour-magnitude and the multiwavelength analysis, we found that PKS 1510-089 (FSRQ) is undergoing an activity phase. For the case of PKS 2005-489 (BL Lac), this blazar is in a quiescent state, in which it has been for more than a decade, and it is compatible with its BWB (bluer-when-brighter) moderate tendency, possibly due to the presence of shocks within the jet.

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The long-term multiwavelength observations of the blazar PKS 2005-489

Cited by 4 publications

References 67 publications

Characterizing the Variable X-Ray and UV–Optical Flux Behavior of Blazars

Characterizing the Variable X-Ray and UV–Optical Flux Behavior of Blazars

Gamma-ray Emission and Variability Processes in High-Energy-Peaked BL Lacertae Objects

Optical monitoring in southern blazars. Analysis of variability and spectral colour behaviours

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