X-ray spectral studies of TeV γ-ray emitting blazars

Wierzcholska, A.; Wagner, S. J.

doi:10.1093/mnras/stw095

Cited by 28 publications

(41 citation statements)

References 172 publications

(150 reference statements)

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“…The results are consistent with the previous studies where for LSPs and ISPs, flatter X-ray spectral slopes varying between 1.5-2 are found (e.g. Donato et al 2005;Massaro et al 2008;Wierzcholska & Wagner 2016).…”

Section: Discussionsupporting

confidence: 93%

“…Raiteri et al (2009) analyzed the XMM−Newton observations of this source during the period 2007-2008 in its low state and found significant concave curvature in all of the observations. Wierzcholska & Wagner (2016) also found the signature of negative curvature in the BL Lac spectrum and found the break energy at ∼1.1 keV. We analyzed three pointings of XMM−Newton and found that the spectra shows an upturn at the break energy of around ∼1.25-1.55 keV.…”

Section: S4 0954+65mentioning

confidence: 78%

“…Donato et al 2005;Tagliaferri et al 2000;Wierzcholska & Wagner 2016). Wierzcholska & Wagner (2016) fitted the Swift/XRT observation of this source using the broken power law and found a break at 2.01 keV.…”

Section: S4 0954+65mentioning

confidence: 95%

“…In ISP blazars, there is a clear turning point in the SED where synchrotron and inverse Compton components intersect e.g. S5 0716+714 ( Giommi et al 1999;Tagliaferri et al 2003;Donato et al 2005;Ferrero et al 2006;Wierzcholska & Siejkowski 2015); ON 231 (Tagliaferri et al 2000); BL Lacertae (Tanihata et al 2000;Ravasio et al 2002); AO 0235+164 (Raiteri et al 2006); OQ 530 (Tagliaferri et al 2003); 3C 66A (Donato et al 2005;Wierzcholska & Wagner 2016); 4C +21.35 (Wierzcholska & Wagner 2016), amongst others.…”

Section: Introductionmentioning

confidence: 99%

“…One expects that FSRQs would have a flatter spectra (index Γ < 2), while the LSPs and ISPs would have intermediate slopes (with index Γ=1.5-1.8), or even concave X-ray continua (e.g. Donato et al 2005;Massaro et al 2008;Wierzcholska & Wagner 2016). In previous studies, it was inferred that the X-ray spectra of blazars is well described by a single power law or a broken power law (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Signature of inverse Compton emission from blazars

Gaur

Mohan

Wierzcholska

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Blazars are classified into high, intermediate and low energy peaked sources based on the location of their synchrotron peak. This lies in infra-red/optical to ultra-violet bands for low and intermediate peaked blazars. The transition from synchrotron to inverse Compton emission falls in the X-ray bands for such sources. We present the spectral and timing analysis of 14 low and intermediate energy peaked blazars observed with XMMNewton spanning 31 epochs. Parametric fits to X-ray spectra helps constrain the possible location of transition from the high energy end of the synchrotron to the low energy end of the inverse Compton emission. In seven sources in our sample, we infer such a transition and constrain the break energy in the range 0.6 10 keV. The Lomb-Scargle periodogram is used to estimate the power spectral density (PSD) shape. It is well described by a power law in a majority of light curves, the index being flatter compared to general expectation from AGN, ranging here between 0.01 and 1.12, possibly due to short observation durations resulting in an absence of long term trends. A toy model involving synchrotron self-Compton (SSC) and external Compton (EC; disk, broad line region, torus) mechanisms are used to estimate magnetic field strength 0.03 -0.88 G in sources displaying the energy break and infer a prominent EC contribution. The timescale for variability being shorter than synchrotron cooling implies steeper PSD slopes which are inferred in these sources.

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Section: Discussionsupporting

confidence: 93%

Section: S4 0954+65mentioning

confidence: 78%

Section: S4 0954+65mentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Signature of inverse Compton emission from blazars

Gaur

Mohan

Wierzcholska

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Hard X-ray properties of NuSTAR blazars

Bhatta

Mohorian

Bilinsky

2018

A&A

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Context. Investigation of the hard X-ray emission properties of blazars is key to the understanding of the central engine of the sources and associated jet process. In particular, simultaneous spectral and timing analyses of the intra-day hard X-ray observations provide us a means to peer into the compact innermost blazar regions, not accessible to our current instruments. Aims. The primary objective of the work is to associate the observed hard X-ray variability properties in the blazars to their flux and spectral states, thereby, based on the correlation among them, extract the details about the emission regions and the processes occurring near the central engine.Methods. We carried out timing, spectral and cross-correlation analysis of 31 NuSTAR observations of 13 blazars. We investigated the spectral shapes of the sources using single power-law, broken power-law and log-parabola models. We also studies the co-relation between the soft and the hard emission using z-transformed discrete correlation function. In addition, we attempted to constrain smallest emission regions using minimum variability timescales derived from the light curves. Results. We found that for most of the sources the hard X-ray emission can be well represented by log-parabola model; and that the spectral slopes for different blazar sub-classes are consistent with so called "blazar sequence". We also report a steepest spectra (Γ ∼ 3 ) in the BL Lacertae PKS 2155-304 and a hardest spectra (Γ ∼ 1.4) in the flat-spectrum radio quasar PKS 2149-306. In addition, we noted a close connection between the flux and spectral slope within the source sub-class in the sense that high flux and/or flux states tend to be harder in spectra. In BL Lacertae objects, assuming particle acceleration by diffusive shocks and synchrotron cooling as the dominant processes governing the observed flux variability, we constrain the magnetic field of the emission region to be a few gauss; whereas in flat-spectrum radio quasars, using external Compton models, we estimate the energy of the lower end of the injected electrons to be a few Lorentz factors.

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Probing the Gamma-Ray Emission Region of Five TeV Flat Spectrum Radio Quasars

Xiao,

Cao,

Xue

et al. 2024

Res. Astron. Astrophys.

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The location of $\gamma$-ray emission of blazars remains a contested topic, inspiring the development of numerous investigative techniques to address this issue.In this work, we analyzed \textit{Fermi} $\gamma$-ray lightcurves in the GeV and MeV bands, employing the discrete cross-correlation function (DCF) method to discern time lags between the two bands.For 4C +21.35, Ton 599, B2 1420+32, and PKS 1510-089, we identified a time lag spanning several days, while for PKS 1441+25, the time lag was not statistically found.The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus (DT) in the first four sources, whereas for PKS 1441+25, they seem to be sourced mainly from the BLR.Further analysis of the opacity ($\tau_{\gamma \gamma}$) and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption. Notably, for PKS 1441+25, the emission region is also posited to lie outside yet proximate to the BLR.The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution (SED) with contemporaneous observation data.Our findings suggest that for the five TeV FSRQs, during TeV flaring events, the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources, with the exceptions of 4C +21.35 and PKS 1441+25.In terms of the overall jet power, particle energy is the dominant contributor, and the observed blazar radiation cannot be solely attributed to the magnetic field, except in the case of 4C +21.35. Consequently, magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.

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X-ray spectral studies of TeV γ-ray emitting blazars

Cited by 28 publications

References 172 publications

Signature of inverse Compton emission from blazars

Signature of inverse Compton emission from blazars

Hard X-ray properties of NuSTAR blazars

Probing the Gamma-Ray Emission Region of Five TeV Flat Spectrum Radio Quasars

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