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Register a new userThe Intrinsic Properties of Multiwavelength Energy Spectra for Fermi Teraelectronvolt Blazars
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In this paper, we have selected a sample of 64 teraelectronvolt blazars, with redshift, from those classified in the fourth Fermi Large Area Telescope source catalogfootnote{url{https://fermi.gsfc.nasa.gov/ssc/data/access/lat/8yr_catalog/}}. We have obtained the values of the relevant physical parameters by performing a log-parabolic fitting of the average-state multiwavelength spectral energy distributions. We estimate the range of the radiation zone parameters, such as the Doppler factor (${D}$), the magnetic field strength ($B$), the radiative zone radius ($R$) and the peak Lorentz factor (${gamma _{rm p}}$) of nonthermal electrons. Here, we show that (1) there is a strong linear positive correlation between the intrinsic synchrotron peak frequency and the intrinsic inverse Compton scattering (ICs) peak frequency among different types of blazars; (2) if radio bands are excluded, the spectral index of each band is negatively correlated with the intrinsic peak frequency; (3) there is a strong linear negative correlation between the curvature at the peak and the intrinsic peak frequency of the synchrotron bump, and a weak positive correlation between the curvature at the peak and the intrinsic peak frequency of the ICs bump; (4) there is a strong linear positive correlation between the intrinsic ICs peak luminosity and intrinsic $gamma$-ray luminosity and between the intrinsic ICs peak frequency and peak Lorentz factor; (5) there is a strong negative linear correlation between $rm log{;B}$ and $rm log{;gamma_{p}}$; and (6) there is no correlation between $rm log{;R}$ and $rm log{;gamma_{p}}$.
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We present multiwavelength spectral analyses of two Fermi-LAT blazars, OJ 287 and 3C 279, that are part of the Boston University multiwaveband polarization program. The data have been compiled from observations with Fermi, RXTE, the VLBA, and various ground-based optical and radio telescopes. We simulate the dynamic spectral energy distributions (SEDs) within the framework of a multi-slice, time-dependent leptonic jet model for blazars, with radiation feedback, in the internal shock scenario. We use the physical jet parameters obtained from the VLBA monitoring to guide our modeling efforts. We discuss the role of intrinsic parameters and the interplay between synchrotron and inverse Compton radiation processes responsible for producing the resultant SEDs.
Beaming effect is important for the observational properties of blazars. In this work, we collect 91 $Fermi$ blazars with available radio Doppler factors. $gamma$-ray Doppler factors are estimated and compared with radio Doppler factors for some sources. The intrinsic (de-beamed) $gamma$-ray flux density ($f^{rm in}_{gamma}$), intrinsic $gamma$-ray luminosity ($L^{rm in}_{gamma}$), and intrinsic synchrotron peak frequency ($ u_{rm p}^{rm in}$) are calculated. Then we study the correlations between $f^{rm in}_{gamma}$ and redshift and find that they follow the theoretical relation: $log f = -2.0 log z + {rm const}$. When the subclasses are considered, we find that stationary jets are perhaps dominant in low synchrotron peaked blazars. 63 $Fermi$ blazars with both available short variability time scales ($Delta T$) and Doppler factors are also collected. We find that the intrinsic relationship between $L ^{rm in}_{gamma}$ and $Delta T^{rm in}$ obeys the Elliot & Shapiro and the Abramowicz & Nobili relations. Strong positive correlation between $f_{gamma}^{rm in}$ and $ u_{rm p}^{rm in}$ is found, suggesting that synchrotron emissions are highly correlated with $gamma$-ray emissions.
Blazars are an extreme subclass of active galactic nuclei. Their rapid variability, luminous brightness, superluminal motion, and high and variable polarization are probably due to a beaming effect. However, this beaming factor (or Doppler factor) is very difficult to measure. Currently, a good way to estimate it is to use the time scale of their radio flares. In this $Letter$, we use multiwavelength data and Doppler factors reported in the literatures for a sample of 86 flaring blazars detected by Fermi to compute their intrinsic multiwavelength data and intrinsic spectral energy distributions, and investigate the correlations among observed and intrinsic data. Quite interestingly, intrinsic data show a positive correlation between luminosity and peak frequency, in contrast with the behavior of observed data, and a tighter correlation between $gamma$-ray luminosity and the lower energy ones. For flaring blazars detected by Fermi, we conclude that (1) Observed emissions are strongly beamed; (2) The anti-correlation between luminosity and peak frequency from the observed data is an apparent result, the correlation between intrinsic data being positive; and (3) Intrinsic $gamma$-ray luminosity is strongly correlated with other intrinsic luminosities.
The curvature of the $gamma$-ray spectrum in blazars may reflect the intrinsic distribution of the emitting electron distribution, which will further give some information on the possible acceleration and cooling processes in the emitting region. The $gamma$-ray spectra of Fermi blazars are normally fitted either by a single power-law (PL) or a log-normal (call Logarithmic Parabola, LP) form. The possible reason for this differnece is not unclear. We statistically explore this issue based on the different observational properties of 1419 Fermi blazars in the 3LAC Clean sample. We find that the $gamma$-ray flux (100 MeV-100 GeV) and variability index follow bimodal distributions for PL and LP blazars, where $gamma$-ray flux and variability index show {a positive correlation}. However, the distributions of the $gamma$-ray luminosity and redshift follow a unimodal distribution. Our results suggest that the bimodal distribution of $gamma$-ray flux for LP and PL blazars may be not intrinsic and all blazars may have an intrinsic curved $gamma$-ray spectrum and the PL spectrum is just caused by the fitting effect due to the less photons.
(Abridged) In this paper, multi-wavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, $log( u F_{ u}) = P_1(log u - P_2)^2 + P_3,$ is used for SED fitting. Synchrotron peak frequency ($log u_p$), spectral curvature ($P_1$), peak flux ($ u_{rm p}F_{rm u_p}$), and integrated flux ($ u F_{ u}$) are successfully obtained for 1392 blazars (461 flat spectrum radio quasars-FSRQs, 620 BL Lacs-BLs and 311 blazars of uncertain type-BCUs, 999 sources have known redshifts). Monochromatic luminosity at radio 1.4 GHz, optical R band, X-ray at 1 keV and $gamma$-ray at 1 GeV, peak luminosity, integrated luminosity and effective spectral indexes of radio to optical ($alpha_{rm RO}$), and optical to X-ray ($alpha_{rm OX}$) are calculated. The Bayesian classification is employed to log$ u_{rm p}$ in the rest frame for 999 blazars with available redshift and the results show that 3 components are enough to fit the $log u_{rm p}$ distribution, there is no ultra high peaked subclass. Based on the 3 components, the subclasses of blazars using the acronyms of Abdo et al. (2010a) are classified, and some mutual correlations are also studied. Conclusions are finally drawn as follows: (1) SEDs are successfully obtained for 1392 blazars. The fitted peak frequencies are compared with common sources from samples available (Sambruna et al. 1996, Nieppola et al. 2006, 2008, Abdo et al. 2010a). (2) Blazars are classified as low synchrotron peak sources (LSPs) if $log u_{rm p}$(Hz) $leq 14.0$, intermediate synchrotron peak sources (ISPs) if $14.0 < log u_{rm p}$(Hz) $leq 15.3$, and high synchrotron peak sources (HSPs) if $log u_{rm p}$(Hz) $> 15.3$. (3) $gamma$-ray emissions are strongly correlated with radio emissions. (...)
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