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

Pandey, Ashwani; Rajput, Bhoomika; Stalin, C. S.

doi:10.48550/arxiv.2111.08247

Cited by 1 publication

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“…The γ-ray lightcurve in Figure 2 is one day binned. There are also reports in the literature that point to varied correlation between optical flux and degree of optical polarization (Gaur et al 2012;Pandey et al 2021).…”

Section: Observation and Data Reductionmentioning

confidence: 98%

Flux and spectral variability of Mrk 421 during its moderate activity state using NuSTAR: Possible accretion disc contribution?

Mondal,

Rani,

Stalin

et al. 2022

Preprint

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Context. The X-ray emission in BL Lac objects is believed to be dominated by synchrotron emission from their relativistic jets. However, when the jet emission is not strong, one could expect signatures of X-ray emission from inverse Compton scattering of accretion disc photons by hot and energetic electrons in the corona. Moreover, the observed X-ray variability can also originate in the disc, and gets propagated and amplified by the jet.Aims. Here, we present results on the BL Lac object Mrk 421 using the Nuclear Spectroscopic Telescope Array data acquired during 2017 when the source was in a moderate X-ray brightness state. For comparison with high jet activity state, we also considered one epoch data in April 2013 when the source was in a very high X-ray brightness state. Our aim is to explore the possibility of the signature of accretion disc emission in the overall X-ray emission from Mrk 421 and also examine changes in accretion parameters considering their contribution to spectral variations. Methods. We divided each epoch of data into different segments in order to find small scale variability. Data for all segments were fitted using simple powerlaw model. We also fitted the full epoch data using the two component advective flow model to extract the accretion flow parameters. Furthermore, we estimated the X-ray flux coming from the different components of the flow using the lowest normalization method and analysed the relations between them. For consistency, we performed the spectral analysis using available models in the literature. Results. The simple powerlaw function does not fit the spectra well, and a cutoff needs to be added. The spectral fitting of the data using the two component advective flow model shows that the data can be explained with a model where (a) the size of the dynamic corona at the base of the jet from ∼ 28 to 10 r s , (b) the disc mass accretion rate from 0.021 to 0.051 ṀEdd , (c) the halo mass accretion rate from 0.22 to 0.35 ṀEdd , and (d) the viscosity parameter of the Keplerian accretion disc from 0.18 − 0.25. In the assumed model, the total flux, disc and jet flux correlate with the radio flux observed during these epochs. Conclusions. From the spectral analysis, we conclude that the spectra of all the epochs of Mrk 421 in 2017 are well described by the accretion disc based two component accretion flow model. The estimated disc and jet flux relations with radio flux show that accretion disc can contribute to the observed X-ray emission, when X-ray data (that covers a small portion of the broad band spectral energy distribution of Mrk 421) is considered in isolation. However, the present disc based models are disfavoured with respect to the relativistic jet models when considering the X-ray data in conjunction with data at other wavelengths.

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Section: Observation and Data Reductionmentioning

confidence: 98%