We study the locations of emission regions through modelling the quasi-simultaneous multi-frequency spectral energy distributions of 21 {\it Fermi} flat spectrum radio quasars (FSRQs) in the frame of a multi-component one-zone leptonic model. In our calculations, we take the detailed broad line region (BLR) structure into account and discuss the effect of the uncertainty of the BLR structure on constraining the location of the emission regions for each FSQR, meanwhile we also include both the internal and external absorptions. Our results indicate that (1) the contribution of external Compton-BLR component is important to $γ$-ray emission, and the energy density of external target photon fields depends on the location of the emission region, which can be derived through reproducing the observed $γ$-ray emission, and (2) the emission regions of FSRQs with relative low accretion disk luminosity lie in the region of $7.9\times10^{16}$\ --\ $1.3\times10^{18}$\ cm (300 -- 4300 Schwarzschild radii) from central black hole, and for FSRQs with high accretion disk luminosity, the emission regions locate in the larger region of $2.6\times10^{17}$\ --\ $4.2\times10^{18}$\ cm (300 -- 5600 Schwarzschild radii).
Flat spectrum radio quasars (FSRQs) are bright active galactic nuclei surrounded by gas clouds within a UV-visible intense radiation field that form the so-called broad line region (BLR). These objects emit relativistic jets from a region close to the central supermassive black hole and through the BLR. The Fermi-Large Area Telescope (Fermi-LAT) is sensitive to gamma-ray photons from $\sim$30 MeV to more than 300 GeV. We have performed spectral analysis of bright FSRQs in a 5.5 year (2008-2014) data sample collected by Fermi-LAT, using the new Pass 8 event selection and instrument response fun…
With the installation of a new 28-m diameter imaging atmospheric Cherenkov telescope in the middle of the array, the H.E.S.S. instrument has entered since 2012 into its Phase II. The fifth large-size telescope is particularly important to lower the threshold energy of the array, and is thus a unique instrument to observe low-frequency-peaked blazars, such as flat-spectrum radio-quasars (FSRQs), which remain rare in the very-high- energy (VHE; E $>$ 100 GeV) $γ$-ray domain. In this contribution, we report on the discovery with the H.E.S.S. telescopes of VHE $γ$-ray emission from the FSRQ PKS 07…
Flat spectrum radio quasars (FSRQs) have been detected at TeV energies by ground-based atmospheric Cherenkov telescopes mainly during flaring states. VERITAS is carrying out the first systematic and unbiased search for TeV emissions from a set of FSRQs. Fermi-LAT-detected FSRQs with positive declinations and extrapolated fluxes from the 3FHL catalog exceeding 1$\%$ Crab at >200 GeV after correcting for EBL absorption were selected for this survey, resulting in eight targets. Additionally, four FSRQs that were already detected at TeV energies are also included in this survey. In an unbiased fas…
We try to infer the location of the GeV emission region for 21 flat spectrum radio quasars (FSRQs) with quasi-simultaneous spectral energy distributions (SEDs), in which the SEDs of 21 FSRQs are reproduced by the one-zone leptonic model including the synchrotron-self Compton (SSC) and external Compton (EC) processes. We suggest that the X-ray emission could be produced by the SSC process and the GeV emission could come from the EC process. The EC emission could originate from the inverse Compton (IC) scattering of photons from the broad line region (BLR) and accretion disk or dust torus by the…
Deviation of the gamma-ray energy spectra of Flat Spectrum Radio Quasars (FSRQs) from a simple power law has been previously observed but the cause of this remains unidentified. If the gamma-ray emission region is close to the central black hole then absorption of gamma-rays with photons from the broad line region is predicted to produce two spectral breaks in the gamma-ray spectra at fixed energies. We examine 9 bright FSRQs for evidence of breaks and curvature. Although we confirm deviation from a simple power law, break energies are usually not where predicted by the double-absorber model. …
We utilize machine learning methods to distinguish BL Lacertae objects (BL Lac) from Flat Spectrum Radio Quasars (FSRQ) within a sample of likely X-ray blazar counterparts to Fermi 3FGL unassociated gamma-ray sources. From our previous work, we have extracted 84 sources that were classified as $\geq$ 99% likley to be blazars. We then utilize Swift$-$XRT, Fermi, and WISE (The Wide-field Infrared Survey Explorer) data together to distinguish the specific type of blazar, FSRQs or BL Lacs. Various X-ray and Gamma-ray parameters can be used to differentiate between these subclasses. These are also …
IceCube has reported the detection of a diffuse TeV-PeV neutrino emission, for which the flat spectrum radio quasars (FSRQs) have been proposed to be the candidate sources. Here we assume that the neutrino flux from FSRQs is proportional to their gamma-ray ones, and obtain the gamma-ray/neutrino flux ratio by the diffuse gamma-ray flux from Fermi-LAT measurement of FSRQs and the diffuse neutrino flux detected by IceCube. We apply this ratio to individual FSRQs and hence predict their neutrino flux. We find that a large fraction of candidate FSRQs from the northern sky in the IceCube point sour…
We revisit the blazar sequence exploiting the complete, flux limited sample of blazars with known redshift detected by the Fermi satellite after 4 years of operations (the 3LAC sample). We divide the sources into gamma-ray luminosity bins, collect all the archival data for all blazars, and construct their spectral energy distribution (SED). We describe the average SED of blazars in the same luminosity bin through a very simple, completely phenomenological function consisting of two broken power laws connecting with a power law of fixed slope describing the radio emission. We do that separately…
The origin and evolution of spectral curvature in blazar spectral energy distribution (SED) is still unclear. Since the observed SED curvature is related to an intrinsic curvature in emitting electron energy distribution (EED), we study this question by employing a log-parabolic EED with a curvature parameter and peak energy to model the quasi-simultaneous broadband SEDs of selected blazars in Fermi-LAT Bright AGN Sample (LBAS) using synchrotron and inverse Compton (IC) processes. We find that log-parabolic IC model can successfully explain the emission in all blazars in our sample. On average…
We present results from a deep VERITAS exposure of the distant (z=0.89) flat-spectrum radio quasar (FSRQ) 4C +55.17. The high flux, hard index and steady emission found by Fermi LAT observations make this blazar a promising very-high-energy (VHE; E>100 GeV) candidate, offering a possibility to clarify the location of FSRQ VHE emission. Non-detection supports the hypothesis that any VHE gamma-rays are produced within and absorbed by the broad-line region while VHE detection would support an emission region outside the broad line region and far from the base of the jet. This FSRQ additionally pr…
We present long term optical and near infrared flux variability analysis of 37 blazars detected in the $γ$-ray band by the {\it Fermi Gamma-Ray Space Telescope}. Among them, 30 are flat spectrum radio quasars (FSRQs) and 7 are BL Lac objects (BL Lacs). The photometric data in the optical (BVR) and infrared (JK) bands were from the Small and Moderate Aperture Research Telescope System acquired between 2008$-$2018. From cross-correlation analysis of the light curves at different wavelengths, we did not find significant time delays between variations at different wavelengths, except for three sou…
Fermi has provided the largest sample of γ-ray selected blazars to date. In this work we use a complete sample of FSRQs detected during the first year of operation to determine the luminosity function (LF) and its evolution with cosmic time. The number density of FSRQs grows dramatically up to redshift \sim0.5-2.0 and declines thereafter. The redshift of the peak in the density is luminosity dependent, with more luminous sources peaking at earlier times; thus the LF of γ-ray FSRQs follows a luminosity-dependent density evolution similarly to that of radio-quiet AGN. Also using data from the Sw…
The gamma-ray energy spectra of bright blazars of the LAT Bright AGN Sample (LBAS) are investigated using Fermi-LAT data. Spectral properties (hardness, curvature and variability) established using a data set accumulated over 6 months of operation are presented and discussed for different blazar classes and subclasses: Flat Spectrum Radio Quasars (FSRQs), Low-synchrotron peaked BLLacs (LSP-BLLacs), Intermediate-synchrotron peaked BLLacs (ISP-BLLacs) and High-synchrotron peaked BLLacs (HSP-BLLacs). The distribution of photon index (obtained from a power-law fit above 100 MeV) is found to correl…
Among the ~2157 unassociated sources in the third data release (DR3) of the fourth Fermi catalog, ~1200 were observed with the Neil Gehrels Swift Observatory pointed instruments. These observations yielded 238 high S/N X-ray sources within the 95% Fermi uncertainty regions. Recently, Kerby et al. employed neural networks to find blazar candidates among these 238 X-ray counterparts to the 4FGL unassociated sources and found 112 likely blazar counterpart sources. A complete sample of blazars, along with their sub-classification, is a necessary step to help understand the puzzle of the blazar seq…
Pinpointing the location of the gamma-ray emitting region in the FSRQ 4C+01.28
Julius-Maximilians-Universität Würzburg（维尔茨堡朱利叶斯-马克西米利安大学）；Max-Planck-Institut für Radioastronomie（马普射电天文研究所）；Center for Astrophysics | Harvard & Smithsonian（哈佛-史密森天体物理中心）；Finnish Centre for Astronomy with ESO (FINCA), University of Turku（图尔库大学芬兰ESO天文中心）；Aalto University（阿尔托大学）；The University of Mississippi（密西西比大学）
Jet origination is one of the most important questions of AGN, yet it stays obscure. In this work, we made use of information of emission lines, spectral energy distributions (SEDs), \textit{Fermi}-LAT $γ$-ray emission, construct a blazar sample that contains 667 sources. We notice that jet power originations are different for BL Lacs and for FSRQs. The correlation between jet power $P_{\rm jet}$ and the normalized disk luminosity $L_{\rm Disk}/L_{\rm Edd}$ shows a slope of -1.77 for BL Lacs and a slope of 1.16 for FSRQs. The results seem to suggest that BL Lac jets are powered by extracting b…
Variability is a typical observation feature of Fermi blazars, sometimes it shows quasi-periodic oscillation (QPO). In this work, we obtained 5-day binned light curves (with a time coverage of $\sim$ 12.9 yr) for S5 1044+71 based on Fermi LAT data, adopted five different methods: Date-compensated Discrete Fourier Transform (DCDFT), Jurkevich (JV), Lomb-Scargle Periodogram (LSP), a Fortran 90 program (REDFIT) and the Weighted Wavelet Z-transform (WWZ) to the $γ$-ray light curve, and found a possible QPO of 3.06 $\pm$ 0.43 yr at the significance level of $\sim3.6σ$. A binary black hole model inc…
During a decade of the $Fermi$-Large Area Telescope (LAT) operation, thousands of blazars have been detected in the $γ$-ray band. However, there are still numbers of blazars that have not been detected in the $γ$-ray band. In this work, we focus on investigating why some flat-spectrum radio quasars (FSRQs) are undetected by $Fermi$-LAT. By cross-matching the Candidate Gamma-ray Blazars Survey catalog with the Fourth Catalog of Active Galactic Nuclei Detected by the $Fermi$-LAT, we select 11 $γ$-ray undetected ($γ$-ray quiet) FSRQs as our sample whose quasi-simultaneous multi-wavelength data ar…
We aim to test if a blazar candidate of uncertain-type (BCU) in the third Fermi active galactic nuclei catalog (3LAC) can be potentially classified as a BL Lac object or a flat spectrum radio quasar (FSRQ) by performing a statistical analysis of its broadband spectral properties. We find that 34% of the radio-selected BCUs (583 BCUs) are BL Lac-like and 20% of them are FSRQ-like, which maybe within 90% level of confidence. Similarly, 77.3% of the X-ray selected BCUs (176 BCUs) are evaluated as BL Lac-like and 6.8% of them may be FSRQ-like sources. And 88.7% of the BL Lac-like BCUs that have sy…
We present a γ-ray photon flux and spectral variability study of the flat-spectrum radio quasar 3C 273 over a rapid flaring activity period between September 2009 to April 2010. Five major flares are observed in the source during this period. The most rapid flare observed in the source has a flux doubling time of 1.1 hr. The rapid γ-ray flares allow us to constrain the location and size of the γ-ray emission region in the source. The γγ-opacity constrains the Doppler factor, $δ_γ \geq$ 10 for the highest energy (15 GeV) photon observed by the {\it Fermi}-Large Area Telescope (LAT). Causality a…
In this work, we collect quasi-simultaneous infrared, optical, X-ray and $γ$-ray data of 60 $Fermi$-4LAC flat spectrum radio quasars (FSRQs). In the framework of the conventional one-zone leptonic model, we investigate the physical properties of $Fermi$-4LAC FSRQs' jets by modeling their quasi-simultaneous spectral energy distributions (SEDs). Our main results are summarized as follows. (1) There is a linear correlation between synchrotron peak frequency and curvature of the electron energy distribution. As suggested by previous works, the slope of the best linear fitting equation of this corr…
Linking {\it Fermi} blazars and radio galaxies through accretion and jet radiation mechanisms
Università di Padova（帕多瓦大学）；Istituto Nazionale di Fisica Nucleare, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）；Guangzhou University（广州大学）；INAF - Istituto di Radioastronomia（意大利国家天体物理研究所射电天文台）；Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province（广东省教育厅天文学科学与技术研究实验室）；Wuhu Vocational Technical University（芜湖职业技术学院）；Institute of Astronomy and National Astronomical Observatory（天文学研究所与国家天文观测站）
Jet Power Estimates of FSRQs PKS 1441+25 and Ton 599 from Broadband SED Modeling
Tezpur University（特佐普尔大学）；Inter-University Centre for Astronomy and Astrophysics（大学间天文与天体物理中心）；Centre for Space Research, North-West University（西北大学空间研究中心）
We report on optical spectroscopy of 165 Flat Spectrum Radio Quasars (FSRQs) in the Fermi 1LAC sample, which have helped allow a nearly complete study of this population. Fermi FSRQ show significant evidence for non-thermal emission even in the optical; the degree depends on the gamma-ray hardness. They also have smaller virial estimates of hole mass than the optical quasar sample. This appears to be largely due to a preferred (axial) view of the gamma-ray FSRQ and non-isotropic (H/R ~ 0.4) distribution of broad-line velocities. Even after correction for this bias, the Fermi FSRQ show higher m…
The deepest all-sky survey available in the $γ$-ray band - the last release of the Fermi-LAT catalogue (4FGL-DR3) based on the data accumulated in 12 years, contains more than 6600 sources. The largest population among the sources is blazar subclass - 3743, $60.1\%$ of which are classified as BL Lacertae objects (BL Lacs) or Flat Spectrum Radio Quasars (FSRQs), while the rest are listed as blazar candidates of uncertain type (BCU) as their firm optical classification is lacking. The goal of this study is to classify BCUs using different machine learning algorithms which are trained on the spec…
Among more than fifty blazars detected in very high energy (VHE, E>100GeV) gamma-rays, only three belong to the subclass of Flat Spectrum Radio Quasars (FSRQs): PKS 1510-089, PKS 1222+216 and 3C 279. The detection of FSRQs in the VHE range is challenging, mainly because of their steep soft spectra in the GeV-TeV regime. MAGIC has observed and detected all FSRQs known to be VHE emitters up to now and found that they exhibit very different behavior. The 2010 discovery of PKS 1222+216 (z = 0.432) with the fast variability observed, challenges simple one-zone emission models and more complicated s…
Recent detection of suborbital gamma-ray variability of Flat Spectrum Radio Quasar (FSRQ) 3C 279 by Fermi Large Area Telescope (LAT) is in severe conflict with established models of blazar emission. This paper presents the results of suborbital analysis of the Fermi/LAT data for the brightest gamma-ray flare of another FSRQ blazar 3C 454.3 in November 2010 (MJD 55516-22). Gamma-ray light curves are calculated for characteristic time bin lengths as short as 3 min. The measured variations of the 0.1-10 GeV photon flux are tested against the hypothesis of steady intraorbit flux. In addition, the …
The blazar zone in quasars is commonly assumed to be located inside the broad-line region at some hundreds of Schwartzschild radii from the central black hole. Now, the simultaneous Fermi/LAT and MAGIC observations of a strong flare in the FSRQ PKS 1222+21 (4C 21.35, z=0.432) on 2010 June 17 challenge this picture. The spectrum can be described by a single power law with photon index 2.72+/-0.34 between 3 GeV and 400 GeV, and this is consistent with emission from a single component in the jet. The absence of a spectral cutoff constrains the gamma-ray emission region to lie outside of the broad…
The γ-ray loud blazars (flat spectrum radio quasars--FSRQs and BL Lacertae objects-BLs) are very bright in the γ-ray bands, which is perhaps associated with a beaming effect. Therefore, one can expect that the γ-ray luminosity is correlated with the beaming factor. In this paper, we investigated the relation between the radio Doppler factors and the gamma-ray luminosities. Our analysis suggests that the γ-ray luminosity be strongly correlated with the factor of δ_R for the whole sample, FSRQs, and BLs. When the effect of a common redshift is excluded, the correlation still exists for the FSRQs…
We have investigated the optical spectral behavior of a large sample of Fermi blazars (40 FSRQs and 13 BL Lacs), and found two new universal optical spectral behaviors. In the low state the optical spectrum gradually becomes softer (steeper) or harder (flatter) but more and more slowly when the brightness increases, and then tends to stable in the high state, which are briefly named the redder-stable-when-brighter (RSWB) and bluer-stable-when-brighter (BSWB) behaviors, respectively. 34 FSRQs and 7 BL Lacs exhibit clear RSWB behavior, and 2 FSRQs and 5 BL Lacs show distinct BSWB behavior, which…
The blazar PKS 1510-089 was the first of the flat spectrum radio quasar type, which had been detected simultaneously by a ground based Cherenkov telescope (H.E.S.S.) and the LAT instrument on board the Fermi satellite. Given the strong broad line region emission defining this blazar class, and the resulting high optical depth for VHE ($E>100\,$GeV) $γ$-rays, it was surprising to detect VHE emission from such an object. In May 2015, PKS 1510-089 exhibited high states throughout the electromagnetic spectrum. Target of Opportunity observations with the H.E.S.S. experiment revealed strong and unpr…
In its first four years of operation, the Fermi Large Area Telescope (LAT) detected 3033 $γ$-ray emitting sources. In the Fermi-LAT Third Source Catalogue (3FGL) about 50% of the sources have no clear association with a likely $γ$-ray emitter. We use an artificial neural network algorithm aimed at distinguishing BL Lacs from FSRQs to investigate the source subclass of 559 3FGL unassociated sources characterised by $γ$-ray properties very similar to those of Active Galactic Nuclei. Based on our method, we can classify 271 objects as BL Lac candidates, 185 as FSRQ candidates, leaving only 103 wi…
In June 2015, the Flat Spectrum Radio Quasar 3C 279 underwent an extremely bright gamma-ray flare, with an increase of the flux above 100 MeV by a factor 10 in less than 1 day, revealing an intrinsic variability timescale of 2 minutes as detected by the Fermi-LAT. We present results of target of opportunity observations with the H.E.S.S. experiment on this source over the nights around the peak of the outburst. The H.E.S.S. data were analysed with mono and stereo chains. Thanks to the extreme brightness of the source at GeV energies, it was possible to obtain data from Fermi-LAT, strictly simu…
The location of $γ$-ray emitting region in blazars has been an open issue for several decades and is still being debated. We use the Paliya et al. sample of 619 $γ$-ray-loud flat-spectrum radio quasars with the available spectral energy distributions, and employ a seed photon factor approach, to locate the $γ$-rays production region. This method efficiently set up a relation between the peak frequencies and luminosities for the synchrotron emission and inverse Compton scattering, together with a combination of the energy density and characteristic energy for the external seed photon field, nam…
We collect the 2LAC and MOJAVE quasi-simultaneous data to investigate the radio-gamma connection of blazars. The cross sample contains 166 sources. The statistic analysis based on this sample confirms positive correlations between these two bands, but the correlations become weaker as the gamma-ray energy increases. The statistic results between various parameters show negative correlations of gamma-ray photon spectral index with gamma-ray loudness for both FSRQs and BL Lacertae objects, positive correlations of gamma-ray variability index with the gamma-ray loudness for FSRQs, a negative corr…
The Fermi Large Area Telescope (LAT) has detected more than 5000 gamma-ray sources in its first 8 years of operation. More than 3000 of them are blazars. About 60 per cent of the Fermi-LAT blazars are classified as BL Lacertae objects (BL Lacs) or Flat Spectrum Radio Quasars (FSRQs), while the rest remain of uncertain type. The goal of this study was to classify those blazars of uncertain type, using a supervised machine learning method based on an artificial neural network, by comparing their properties to those of known gamma-ray sources. Probabilities for each of 1329 uncertain blazars to b…
In this work, Machine Learning (ML) methods are used to efficiently identify the unassociated sources and the Blazar Candidate of Uncertain types (BCUs) in the Fermi-LAT Third Source Catalog (3FGL). The aims are twofold: 1) to distinguish the Active Galactic Nuclei (AGNs) from others (non-AGNs) in the unassociated sources; 2) to identify BCUs into BL Lacertae objects (BL Lacs) or Flat Spectrum Radio Quasars (FSRQs). Two dimensional reduction methods are presented to decrease computational complexity, where Random Forest (RF), Multilayer Perceptron (MLP) and Generative Adversarial Nets (GAN) ar…
The flat spectrum radio quasar (FSRQ) PKS 1510-089 (z=0.361) is known for its complex multiwavelength behavior. It has been monitored regularly at very high energy (VHE, $E>100\,$GeV) gamma-rays with H.E.S.S. since its discovery in 2009 in order to study the unknown behavior of FSRQs in quiescence at VHE, as well as the flux evolution around flaring events. Given the expected strong cooling of electrons and the absorption of VHE emission within the broad-line region, a detection of PKS 1510-089 at VHE in a quiescent state would be an important result, implying an acceleration and emission regi…
Knowing the site of gamma-ray emission in AGN jets will do much for our understanding of the physics of the source. In particular, if the emission region is close to the black hole then absorption of gamma-rays with photons from the broad-line region could become significant. Such absorption is predicted to produce two specific spectral breaks in the gamma-ray spectra of Flat Spectrum Radio Quasars (FSRQs). We test this hypothesis using 3 years of Fermi observations of nine bright FSRQs. A simple power law fit to the spectrum of each source can be significantly improved by introducing a break,…
Flat spectrum radio quasar (FSRQ) is the most luminous blazar at the GeV energies. In this paper, we probe the photon-axion-like particle (ALP) oscillation effect on the latest very-high-energy (VHE) $γ$-ray observations of the FSRQ 4C+21.35 (PKS 1222+216). The $γ$-ray spectra are measured by the collaborations Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC), Very Energetic Radiation Imaging Telescope Array System (VERITAS), and Fermi Large Area Telescope (Fermi-LAT), which cover two activity VHE flares of 4C+21.35 in 2010 and 2014. We show the spectral energy distributions (SEDs)…
The expected level of gamma-gamma absorption in the Broad Line Region (BLR) radiation field of gamma-ray loud Flat Spectrum Radio Quasars (FSRQs)is evaluated as a function of the location of the gamma-ray emission region. This is done self-consistently with parameters inferred from the shape of the spectral energy distribution (SED) in a single-zone leptonic EC-BLR model scenario. We take into account all geometrical effects both in the calculation of the gamma-gamma opacity and the normalization of the BLR radiation energy density. As specific examples, we study the FSRQs 3C279 and PKS 1510-0…
We study the correlation between gamma-ray and radio band radiation for 123 blazars, using the Fermi-LAT first source catalog (1FGL) and the RATAN-600 data obtained at the same period of time (within a few months). We found an apparent positive correlation for BL Lac and flat-spectrum radio quasar (FSRQ) sources from our sample through testing the value of the Pearson product-moment correlation coefficient. The BL Lac objects show higher values of the correlation coefficient than FSRQs at all frequencies, except 21.7 GHz, and at all bands, except $10-100$ GeV, typically at high confidence leve…
Detailed investigation of broadband flux variability in the blazar 3C 273 allows us to probe the location and size of emission regions and their physical conditions. We report the results on correlation studies of the flaring activity observed between 2008 and 2012. The observed broadband variations were investigated using the structure function and the discrete correlation function, and power spectral density analysis (PSD) methods. The PSD analysis showed that the optical/IR light curve slopes are consistent with the slope of white noise processes, while, the PSD slopes at radio, X-ray and g…
We present a temporal and spectral analysis of the gamma-ray flux from nine of the brightest flat spectrum radio quasars (FSRQs) detected with the Fermi Large Area Telescope (LAT) during its first eight years of operation, with the aim of constraining the location of the emission region. Using the increased photon statistics provided from the two brightest flares of each source, we find evidence of sub-hour variability from B2 1520+31, PKS 1502+106 and PKS 1424-41, with the remaining sources showing variability on timescales of a few hours. These indicate gamma-ray emission from extremely comp…
We have recently proposed a new simplified scenario where blazars are classified as flat-spectrum radio quasars (FSRQs) or BL Lacs according to the prescriptions of unified schemes, and to a varying combination of Doppler boosted radiation from the jet, emission from the accretion disk, the broad line region, and light from the host galaxy. Here we extend our approach, previously applied to radio and X-ray surveys, to the gamma-ray band and, through detailed Monte Carlo simulations, compare our predictions to Fermi-LAT survey data. Our simulations are in remarkable agreement with the overall o…
In this paper, we characterize the first $γ$-ray flaring episode of the FSRQ PKS 0346-27 (z=0.991), as revealed by Fermi-LAT monitoring data, and the concurrent multi-wavelength variability observed from radio through X-rays. The quasi-simultaneous multi-wavelength coverage allowed us to construct time-resolved spectral energy distributions (SEDs). PKS 0346-27 entered an elevated $γ$-ray activity state starting from the beginning of 2018. The high-state continued throughout the year, displaying the highest fluxes in May 2018. We find evidence of short-time scale variability down to $\sim$1.5 h…
Aiming to delineate the physical framework of blazars, we present an effective method to estimate four important parameters based on the idea proposed by \citet{BK95}, including the upper limit of central black hole mass $M$, the Doppler factor $δ$, the distance along the axis to the site of the $γ$-ray production $d$ (which then can be transformed into the location of $γ$-ray-emitting region $R_γ$) and the propagation angle with respect to the axis of the accretion disk $Φ$. To do so, we adopt an identical sample with 809 {\it Fermi}-LAT-detected blazars which had been compiled in \citet{Pei2…
[abridged] We present results of modeling the SED and multiwavelength variability of the bright FSRQ PKS1510-089 with our time-dependent multizone Monte Carlo/Fokker-Planck code (Chen et al. 2001). As primary source of seed photons for inverse Compton scattering, we consider radiation from the broad line region (BLR), from the molecular torus, and the local synchrotron radiation (SSC). Different scenarios are assessed by comparing simulated light curves and SEDs with one of the best flares by PKS1510-089, in March 2009. The time-dependence of our code and its correct handling of light travel t…
