The lower limit of the Doppler factor for a Fermi blazar sample

Fan, J. H.; Bastieri, D.; Yang, Jiang-He; Liu, Yi; Tao, Hua; Yuan, Yu-Hai; Wu, Di

doi:10.1088/1674-4527/14/9/004

Cited by 64 publications

(81 citation statements)

References 54 publications

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“…In this paper, we estimate the lower limit on γ-ray Doppler factors for those γ-ray blazars following Mattox et al (1993) as did in Fan et al (2013aFan et al ( , 2014, probing their relations and shedding new light on the relativistic beaming effect of γ-ray loud blazars. The methodology is discussed in Section 2, while in Section 3 we describe the sample and results.…”

Section: Introductionmentioning

confidence: 91%

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The estimation of γ-ray Doppler factor forFermi/LAT-detected blazars

Pei

Jiang

Yang

et al. 2020

Publ. Astron. Soc. Aust.

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Blazars are a subclass of active galactic nuclei with extreme observation properties, which is caused by the beaming effect, expressed by a Doppler factor ( $\delta$ ), in a relativistic jet. Doppler factor is an important parameter in the blazars paradigm to indicate all of the observation properties, and many methods were proposed to estimate its value. In this paper, we present a method following Mattox et al. to calculate the lower limit on $\gamma$ -ray Doppler factor ( $\delta_{\gamma}$ ) for 809 selected Fermi/LAT-detected $\gamma$ -ray blazars by adopting the available $\gamma$ -ray and X-ray data. Our sample included 342 flat-spectrum radio quasars (FSRQs) and 467 BL Lac objects (BL Lacs), out of which 507 sources are compiled with available radio core-dominance parameter (R) from our previous study. Our calculation shows that the average values of the lower limit on $\delta_{\gamma}$ for FSRQs and BL Lacs are $\left\langle\delta_{\gamma}|_{\textrm{FSRQ}}\right\rangle = 6.87 \pm 4.07$ and $\left\langle\delta_{\gamma}|_{\textrm{BL\ Lac}}\right\rangle=4.31 \pm 2.97$ , respectively. We compare and discuss our results with those from the literature. We found that the derived lower limit on $\delta_{\gamma}$ for some sources is higher than that from the radio estimation, which could be possibly explained by the jet bending within those blazars. Our results also suggest that the $\gamma$ -ray and radio regions perhaps share the same relativistic effects. The $\gamma$ -ray Doppler factor has been found to be correlated with both the $\gamma$ -ray luminosity and core-dominance parameter, implying that the jet is possibly continuous in the $\gamma$ -ray bands, and R is perhaps an indicator for a beaming effect.

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Section: Introductionmentioning

confidence: 91%

“…The variability timescales for most sources are unknown, even though a few ones are available (Yang & Fan 2010). In our calculation, for the sake of simplicity, we adopt T=1 d (Dondi & Ghisellini 1995;Ghisellini et al 1998;Fan et al 2013aFan et al , 2014. Consequently, we can calculate the lower limit on γ-ray Doppler factor δ γ .…”

Section: Calculationmentioning

confidence: 99%

The estimation of γ-ray Doppler factor forFermi/LAT-detected blazars

Pei

Jiang

Yang

et al. 2020

Publ. Astron. Soc. Aust.

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“…The calculation of γ-ray opacity Doppler factors is based on the requirement that the γ−ray emission region must be transparent to gamma rays (Mattox et al 1993;Fan et al 2013Fan et al , 2014. The process responsible for γ-ray absorption is pair production due to the interaction between γ-ray photons and X-ray photons.…”

Section: Gamma-ray Opacity Doppler Factorsmentioning

confidence: 99%

Population statistics of beamed sources – II. Evaluation of Doppler factor estimates

Liodakis

Pavlidou

2015

Mon. Not. R. Astron. Soc.

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In a companion paper we presented a statistical model for the blazar population, consisting of distributions for the unbeamed radio luminosity function and the Lorentz factor distribution of each of the BL Lac and Flat Spectrum Radio Quasar (FSRQ) classes. Our model has been optimized so that it reproduces the MOJAVE distributions of apparent speeds and redshifts when the appropriate flux limit is applied and a uniform distribution of jet viewing angles is assumed for the population. Here we use this model to predict the Doppler factor distribution for various flux-limited samples for which Doppler factors have been estimated in a variety of ways (equipartition, variability + equipartition, inverse Compton dominance) on a blazar-by-blazar basis. By comparing the simulated and data-estimated Doppler factor distributions in each case, we evaluate the different methods of estimating blazar Doppler factors. We find that the variability Doppler factors assuming equipartition are the ones in the best agreement with our statistical model, whereas the inverse Compton Doppler factor method is only suitable for FSRQs. In the case of variability Doppler factors, we find that while random errors are relatively low (∼ 30%), uncertainties are dominated by systematic effects. In the case of inverse Compton Doppler factors, random errors appear to dominate, but are significantly larger (∼ 60%).

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“…The difference between the two subclasses is mainly that BL Lacertae objects show very weak (or even no) emission line features while FSRQs display strong emission lines. However, the continuum emission properties of BL Lacs and FSRQs are quite similar (Zhang & Fan 2003;Fan et al 2009Fan et al , 2014aXiao et al 2015). BL Lac objects were separately discovered through radio or X-ray surveys, and were divided into radio selected BL Lacertae objects (RBLs) and X-ray selected BL Lacertae objects (XBLs).…”

Section: Introductionmentioning

confidence: 87%

“…Observations suggest that γ-ray loud blazars are variable on time scales of hours although there is no preferred scale for the variation time of any source (Fan et al 2014a). For example, Fermi LAT detected a variability time scale of ∼12 hour for PKS 1454 − 354 (Abdo et al 2009), and a doubling time of roughly 4 hours for PKS 1502+105 (Abdo et al 2010c).…”

Section: Short Variability Time Scale and Luminositymentioning

confidence: 99%

The intrinsicγ-ray emissions ofFermiblazars

Lin

Jiang

Xiao

2017

Res. Astron. Astrophys.

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Beaming effect is important for the observational properties of blazars. In this work, we collect 91 F ermi blazars with available radio Doppler factors. γ-ray Doppler factors are estimated and compared with radio Doppler factors for some sources. The intrinsic (de-beamed) γ-ray flux density (f in γ ), intrinsic γ-ray luminosity (L in γ ), and intrinsic synchrotron peak frequency (ν in p ) are calculated. Then we study the correlations between f in γ and redshift and find that they follow the theoretical relation: log f = −2.0 log z + const. When the subclasses are considered, we find that stationary jets are perhaps dominant in low synchrotron peaked blazars. 63 F ermi blazars with both available short variability time scales (∆T ) and Doppler factors are also collected. We find that the intrinsic relationship between L

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The lower limit of the Doppler factor for a Fermi blazar sample

Cited by 64 publications

References 54 publications

The estimation of γ-ray Doppler factor forFermi/LAT-detected blazars

The estimation of γ-ray Doppler factor forFermi/LAT-detected blazars

Population statistics of beamed sources – II. Evaluation of Doppler factor estimates

The intrinsicγ-ray emissions ofFermiblazars

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