Correlation between optical and γ-ray flux variations in bright flat spectrum radio quasars

Rajput, Bhoomika; Stalin, C. S.; Sahayanathan, S.

doi:10.1093/mnras/staa2708

Cited by 26 publications

(18 citation statements)

References 115 publications

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“…Based on Figure 11, it can be understood that sources lying around CD ≈1 and L disk /L Edd ≈0.01 may belong to the family of masquerading BL Lacs. We stress that our physical interpretation of the obtained CD and L disk /L Edd correlation may not be extendable to blazar flares which can be extremely complex and diverse (e.g., Rajput et al 2020). This is because we used multiwavelength SEDs generated using all archival observations to compute CD hence reflect the average activity state of sources.…”

Section: Compton Dominance Measurementmentioning

confidence: 95%

The Central Engines of Fermi Blazars

Paliya,

Domínguez,

Ajello

et al. 2021

Preprint

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We present a catalog of central engine properties, i.e., black hole mass (M BH ) and accretion luminosity (L disk ), for a sample of 1077 blazars detected with the Fermi Large Area Telescope. This includes broad emission line systems and blazars whose optical spectra lack emission lines but dominated by the absorption features arising from the host galaxy. The average M BH for the sample is log M BH,all M = 8.60 and there are evidences suggesting the association of more massive black holes with absorption line systems. Our results indicate a bi-modality of L disk in Eddington units (L disk /L Edd ) with broad line objects tend to have a higher accretion rate (L disk /L Edd >0.01). We have found that L disk /L Edd and Compton dominance (CD, the ratio of the inverse Compton to synchrotron peak luminosities) are positively correlated at >5σ confidence level, suggesting that the latter can be used to reveal the state of accretion in blazars. Based on this result, we propose a CD based classification scheme. Sources with CD>1 can be classified as High-Compton Dominated or HCD blazars, whereas, that with CD 1 are Low-Compton Dominated (LCD) objects. This scheme is analogous to that based on the mass accretion rate proposed in the literature, however, it overcomes the limitation imposed by the difficulty in measuring L disk and M BH for objects with quasi-featureless spectra. We conclude that the overall physical properties of Fermi blazars are likely to be controlled by the accretion rate in Eddington units. The catalog is made public at http://www.ucm.es/blazars/engines and Zenodo.

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Section: Compton Dominance Measurementmentioning

confidence: 95%

The Central Engines of Fermi Blazars

Paliya,

Domínguez,

Ajello

et al. 2021

Preprint

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“…However, assuming the cooling of the particle by synchrotron and inverse-Compton of external radiation field, depending upon the profile of those parameters along the jet, both soft or hard lag can occur (see Janiak et al 2012). In any case, study of the individual flares in multiple emission bands, especially orphan flares (e. g. see Rajput et al 2020), could provide further details necessary to identify the dominant process operating in blazar jets (see Liodakis et al 2019).…”

Section: • Optical Variability In Blazarsmentioning

confidence: 99%

Characterizing Long-term Optical Variability Properties of $γ$-ray Bright Blazars

Bhatta

2021

Preprint

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Optical observations of a sample of 12 γ-ray bright blazars from four optical data archives, AAVSO, SMARTS, Catalina, and Steward Observatory, are compiled to create densely sampled light curves spanning more than a decade. As a part of the blazar multi-wavelength studies, several methods of analyses, e. g., flux distribution and RMS-flux relation, are performed on the observations with an aim to compare the results with the similar ones in the γ-ray band presented in Bhatta & Dhital (2020). It is found that, similar to γ-ray band, blazars display significant variability in the optical band that can be characterized with log-normal flux distribution and a power-law dependence of RMS on flux. It could be an indication of possible inherent linear RMS-flux relation, yet the scatter in the data does not allow to rule out other possibilities. When comparing variability properties in the two bands, the blazars in the γ-rays are found to exhibit stronger variability with steeper possible linear RMS-flux relation and the flux distribution that is more skewed towards higher fluxes. The crosscorrelation study shows that except for the source 3C 273, the overall optical and the γ-ray emission in the sources are highly correlated, suggesting a co-spatial existence of the particles responsible for both the optical and γ-ray emission. Moreover, the sources S5 0716+714, Mrk 421, Mrk 501, PKS 1424-418 and PKS 2155-304 revealed possible evidence for quasi-periodic oscillations in the optical emission with the characteristic timescales, which are comparable to those in the γ-ray band detected in our previous work.

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“…Changes in the observed polarization position angle could be related to changes in the direction of the magnetic field in the jet along the observer's line of sight. Moreover, as the flux variations in the optical and GeV 𝛾-rays are connected (Bonning et al 2009;Chatterjee et al 2012;Liao et al 2014;Carnerero et al 2015;Patiño-Álvarez et al 2018;Chavushyan et al 2020;Amaya-Almazán et al 2021, however, see also Rajput et al (2019Rajput et al ( , 2020a and references therein for no correlation between optical and 𝛾-ray flux variations) flux and polarization variability observations at different wavelengths can provide important inputs on the connection between different emission regions in the jets of these sources. Also, observations with the Fermi Gamma-ray Space Telescope (hereinafter Fermi) have revealed a close association between the 𝛾-ray flare and the rotation of the optical polarization position angle, which again can constrain the nature of the high energy 𝛾-ray emission process (Marscher et al 2008;Abdo et al 2010a;Marscher et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Correlation between optical flux and polarization variations in Flat Spectrum Radio Quasars on diverse timescales

Pandey,

Rajput,

Stalin

2021

Preprint

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Study of the polarization behaviour in blazars is a powerful tool to discern the role of magnetic field in the variable emission process in their relativistic jets. We present here results of our systematic investigation on the correlation between optical flux and polarization variations for eight flat spectrum radio quasars on various timescales using data from the Steward Observatory that covers a period of ∼10 years. On long time scales (∼several months), from a total of 79 observing cycles, in 34 observing cycles, we found a significant positive correlation between optical flux and optical polarization degree (PD), negative correlation in 3 cycles and no correlation in 42 cycles. On short time scales (∼few days), in 47 out of a total of 55 epochs, we found a positive correlation between optical flux and PD, while, on the remaining 8 epochs, an anti-correlation was detected between the two quantities. Moreover, we noticed a significant positive correlation between optical and 𝛾−ray fluxes on 14 epochs and a negative correlation between the two on one epoch. While the observed optical flux changes well fit in the shock-in-jet model, the observed changes in PD are not explainable by changes in the power-law spectral index of the relativistic electrons in the jet. Instead, the observed varied correlations between optical flux and PD could be due to multi-zone emission regions or the enhanced flux coinciding with the emergence of a new emission knot with its magnetic field either aligned or misaligned with the large scale magnetic field.

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Correlation between optical and γ-ray flux variations in bright flat spectrum radio quasars

Cited by 26 publications

References 115 publications

The Central Engines of Fermi Blazars

The Central Engines of Fermi Blazars

Characterizing Long-term Optical Variability Properties of $γ$-ray Bright Blazars

Correlation between optical flux and polarization variations in Flat Spectrum Radio Quasars on diverse timescales

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