X-ray Flux and Spectral Variability of Blazar H 2356-309

Kiran A Wani,Haritma Gaur

doi:10.3390/galaxies8030059

Abstract

We present the results of timing and spectral analysis of the blazar H 2356-309 using XMM-Newton observations. This blazar is observed during 13 June 2005–24 December 2013 in total nine observations. Five of the observations show moderate flux variability with amplitude 1.7–2.2%. We search for the intra-day variability timescales in these five light curves, but did not find in any of them. The fractional variability amplitude is generally lower in the soft bands than in the hard bands, which is attributed to the energy dependent synchrotron emission. Using the hardness ratio analysis, we search for the X-ray spectral variability along with flux variability in this source. However, we did not find any significant spectral variability on intra-day timescales. We also investigate the X-ray spectral curvature of blazar H 2356-309 and found that six of our observations are well described by the log parabolic model with α = 1.99–2.15 and β = 0.03–0.18. Three of our observations are well described by power law model. The break energy of the X-ray spectra varies between 1.97–2.31 keV. We investigate the correlation between various parameters that are derived from log parabolic model and their implications are discussed.

Highlights

Blazars are highly luminous AGNs (Active Galactic Nuclei) that emit in all accessible wavelengths ranging from radio to high energy gamma rays
F-test results that six out of nine observations of the blazar are well described by the log parabolic (LP) model, where α varies between 1.99–2.15 and curvature β varies between 0.03–0.18
We studied nine XMM–Newton observations of the HSP blazar H 2356-309, which are available in its public archive

Summary

Introduction

Blazars are highly luminous AGNs (Active Galactic Nuclei) that emit in all accessible wavelengths ranging from radio to high energy gamma rays. Blazars show very strong continuum with featurless optical spectrum, which is thought to be due to relativistic jets pointing nearly to our line of sight (≤10◦ ) [1]. The broadband spectral energy distribution of blazar is characterized by a double peaked structure. The first hump at lower energies is attribued to the synchrotron emission from relativistic electrons in a jet, while the high frequency hump is thought to be produced by inverse Compton scattering from the same electron population with the synchrotron photons (SSC, Synchrotron Self Compton models; e.g., [2]) or with external ambient photons originated in the BLR (Broad Line region), torus (EC, External Compton models; e.g., [3]). The peak of the low-energy spectral component is found at

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Discussion

Conclusion