scholarly journals Theγ-ray emitting region in low synchrotron peak blazars

2018 ◽  
Vol 616 ◽  
pp. A63 ◽  
Author(s):  
B. Arsioli ◽  
Y-L. Chang
Keyword(s):  
Spectral Energy Distribution ◽  
Thomson Scattering ◽  
High Energy ◽  
Spectral Energy ◽  
Electromagnetic Spectrum ◽  
X Rays ◽  
Complete Sample ◽  
Central Engine ◽  
Line Region ◽  
Open Question

Aims.From the early days inγ-ray astronomy, locating the origin of GeV emission within the core of an active galactic nucleus (AGN) persisted as an open question; the problem is to discern between near- and far-site scenarios with respect to the distance from the super massive central engine. We investigate this question under the light of a complete sample of low synchrotron peak (LSP) blazars which is fully characterized along many decades in the electromagnetic spectrum, from radio up to tens of GeV. We consider the high-energy emission from bright radio blazars and test for synchrotron self-Compton (SSC) and external Compton (EC) scenarios in the framework of localizing theγ-ray emission sites. Given that the inverse Compton (IC) process under the EC regime is driven by the abundance of external seed photons, these photons could be mainly ultraviolet (UV) to X-rays coming from the accretion disk region and the broad-line region (BLR), therefore close to the jet launch base; or infrared (IR) seed photons from the dust torus and molecular cloud spine-sheath, therefore far from jet launch base. We investigate both scenarios, and try to reveal the physics behind the production ofγ-ray radiation in AGNs which is crucial in order to locate the production site.Methods.Based on a complete sample of 104 radio-selected LSP blazars, with 37 GHz flux density higher than 1 Jy, we study broadband population properties associated with the nonthermal jet emission process, and test the capability of SSC and EC scenarios to explain the overall spectral energy distribution (SED) features. We use SEDs well characterized from radio toγrays, considering all currently available data. The enhanced available information from recent works allows us to refine the study of Syn to IC peak correlations, which points to a particularγ-ray emission site.Results.We show that SSC alone is not enough to account for the observed SEDs. Our analysis favors an EC scenario under the Thomson scattering regime, with a dominant IR external photon field. Therefore, the far-site (i.e., far from the jet launch) is probably the most reasonable scenario to account for the population properties of bright LSP blazars in cases modeled with a pure leptonic component. We calculate the photon energy density associated with the external field at the jet comoving frame to beU′ext= 1.69 × 10−2erg cm−3, finding good agreement to other correlated works.

scholarly journals A complete sample of LSP blazars fully described in γ-rays

2018 ◽  
Vol 616 ◽  
pp. A20 ◽  
Author(s):  
B. Arsioli ◽  
G. Polenta
Keyword(s):  
Peak Power ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Full Description ◽  
X Rays ◽  
Test Statistic ◽  
Complete Sample ◽  
Frequency Distributions ◽  
Source Confusion

Context. We study the γ-ray and broadband spectral energy distribution (SED) properties of a complete sample of 104 bright, radio-selected low-synchrotron peaked (LSP) blazars, which have well-characterized SEDs from radio to X-rays. Most of the sources have already been detected in the γ-ray band by Fermi-LAT, however almost 20% of these blazars have no counterpart in any of the Fermi catalogs published so far. Aims. Using the Fermi Science Tools, we look for γ-ray emission for those objects not yet reported in any Fermi-LAT catalog, finding new detections and associations. We then study the multifrequency SED for all sources in our sample, fitting their synchrotron (Syn) and inverse Compton (IC) components. A complete sample of LSP blazars with a full description in γ-ray is unique. We use this sample to derive the distribution of the Compton dominance (CD) along with population properties such as Syn and IC peak power, and frequency distributions. Methods. We performed a binned likelihood analysis in the 0.3–500 GeV energy band with Fermi-LAT Pass 8 data, integrating over 7.5 yr of observations. We studied γ-ray light curves and test statistic (TS) maps to validate new detections and associations, thereby building a better picture of the high-energy activity in radio-selected LSP blazars. We fit the IC component for the new detections using all data at our disposal from X-rays to GeV γ-rays, enhancing the amount of information available to study the Syn to IC peak-power correlations. Results. We deliver a unique characterization in γ-rays for a complete sample of LSP blazars. We show that three previously unidentified 3FGL sources can be associated with blazars when using improved γ-ray positions obtained from TS maps. Six previously unreported γ-ray sources are detected at TS > 20 level, while another three show TS values between 10–20. We evaluate two cases in which source confusion is likely present. In four cases there is no significant γ-ray signature when integrating over 7.5 yr. Short-lived flares at ~1 month scale, however, have been detected in these sources. Finally, we measure the log(CD) for the sample, which has a Gaussian-like distribution with median log(CD) ≈ 0.1, implying that on average the peak-power for the Syn and IC components in LSP blazars is similar.

scholarly journals Monitoring of the radio galaxy M 87 at Very High Energy with MAGIC during a low emission state between 2012 and 2015

2016 ◽  
Vol 12 (S324) ◽  
pp. 164-167
Author(s):  
C. Arcaro ◽  
P. Bangale ◽  
M. Manganaro ◽  
D. Mazin ◽  
P. Colin ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Spectral Energy Distribution ◽  
Photon Emission ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Low Emission ◽  
Very High Energy ◽  
Alternative Scenarios ◽  
Very High

AbstractWe present the preliminary results from observing the nearby radio galaxy M 87 for 156 hours (between the years 2012 and 2015) with the MAGIC telescopes, which lead to a significant very high energy (VHE, E > 100 GeV) detection of the source in quiescent states each year. Our VHE analysis combined with quasi-simultaneous data at other energies (from gamma-rays, X-rays, optical and radio) provides a unique opportunity to study the source variability and its broadband spectral energy distribution, which is found to disfavour a one-zone synchrotron/synchrotron self-Compton model. Therefore, other alternative scenarios for the photon emission are explored. We also find that the VHE emission is compatible with being produced close to the source radio core as previous data already indicated. A detailed paper presenting full results of the observing campaign is in preparation.

scholarly journals A NuSTAR view of powerful γ-ray loud blazars

2019 ◽  
Vol 627 ◽  
pp. A72 ◽  
Author(s):  
G. Ghisellini ◽  
M. Perri ◽  
L. Costamante ◽  
G. Tagliaferri ◽  
T. Sbarrato ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Peak Frequency ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Γ Ray ◽  
The Universe ◽  
Jet Power

We observed three blazars at z >  2 with the NuSTAR satellite. These were detected in the γ-rays by Fermi/LAT and in the soft X-rays, but have not yet been observed above 10 keV. The flux and slope of their X-ray continuum, together with Fermi/LAT data allows us to estimate their total electromagnetic output and peak frequency. For some of them we were able to study the source in different states, and investigate the main cause of the different observed spectral energy distribution. We then collected all blazars at redshifts greater than 2 observed by NuSTAR, and confirm that these hard and luminous X-ray blazars are among the most powerful persistent sources in the Universe. We confirm the relation between the jet power and the disk luminosity, extending it at the high-energy end.

scholarly journals THE FSRQs 3C 279 AND PKS 1510-089: MAGIC LATEST RESULTS AND MULTIWAVELENGTH OBSERVATIONS

2014 ◽  
Vol 28 ◽  
pp. 1460176 ◽  
Author(s):  
◽  
G. DE CANEVA ◽  
U. BARRES DE ALMEIDA ◽  
E. LINDFORS ◽  
K. SAITO ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Spectrum Radio ◽  
Upper Limits ◽  
Very High Energy ◽  
Γ Rays ◽  
Differential Flux ◽  
Multiwavelength Observations

At very high energy (VHE, E> 100 GeV), we count only three blazars of the flat spectrum radio quasars (FSRQs) type to date. The MAGIC experiment detected all three of them; here we present MAGIC observations of 3C 279 and PKS 1510-089. 3C 279 was observed in 2011, without a significant detection, hence upper limits on the differential flux have been computed. The MAGIC observations of PKS 1510-089 in 2012 were triggered by alerts of high activity states and resulted in a significant detection. MAGIC observations are complemented with simultaneous multiwavelength observations in high energy γ rays, X-rays, optical and radio wavelengths and polarization measurements. With the study of the spectral features and the variability observed, we aim to identify the physical processes responsible for the behavior of this source class. In particular, we propose coherent scenarios, which take into account both the modeling of the spectral energy distribution and the constraints obtained from the lightcurves.

scholarly journals Centaurus A at Hard X-Rays and Soft Gamma-Rays

2010 ◽  
Vol 27 (4) ◽  
pp. 431-438 ◽  
Author(s):  
H. Steinle
Keyword(s):  
Energy Range ◽  
Spatial Resolution ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Satellite Mission ◽  
X Ray

AbstractCen A, at a distance of less than 4 Mpc, is the nearest radio-loud AGN. Its emission is detected from radio to very-high energy gamma-rays. Despite the fact that Cen A is one of the best studied extragalactic objects the origin of its hard X-ray and soft gamma-ray emission (100 keV <E< 50 MeV) is still uncertain. Observations with high spatial resolution in the adjacent soft X-ray and hard gamma-ray regimes suggest that several distinct components such as a Seyfert-like nucleus, relativistic jets, and even luminous X-ray binaries within Cen A may contribute to the total emission in the MeV regime that has been detected with low spatial resolution. As the Spectral Energy Distribution of Cen A has its second maximum around 1 MeV, this energy range plays an important role in modeling the emission of (this) AGN. As there will be no satellite mission in the near future that will cover this energies with higher spatial resolution and better sensitivity, an overview of all existing hard X-ray and soft gamma-ray measurements of Cen A is presented here defining the present knowledge on Cen A in the MeV energy range.

HIGH-ENERGY PARTICLE INTERACTIONS IN THE INNER JET OF THE RADIO GALAXY M87

2010 ◽  
Vol 19 (06) ◽  
pp. 957-963
Author(s):  
CHLOÉ GUENNOU ◽  
GUSTAVO E. ROMERO ◽  
GABRIELA S. VILA
Keyword(s):  
Gamma Ray ◽  
Radio Galaxy ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
High Energy Particle ◽  
Zone Model ◽  
Rapid Variability ◽  
Central Engine ◽  
Energy Gamma

Recent observations with the High Energy Stereoscopic System (HESS) have revealed strong and variable high energy gamma-ray emission from the radio galaxy M87. The origin of such emission is uncertain, but the rapid variability indicates that it should be produced close to the central engine of the source. In this work, a lepto-hadronic one-zone model is applied to the available multiwavelength data of M87. The different energy losses for both primary and secondary particles are calculated. Then, the different contributions to the spectral energy distribution through interactions with matter, radiation and magnetic fields are obtained, in good accordance with the observations.

MODELING THE MULTIWAVELENGTH SPECTRA AND VARIABILITY OF 3C 66A IN 2003–2004

2007 ◽  
Vol 22 (19) ◽  
pp. 3147-3154
Author(s):  
M. JOSHI ◽  
M. BÖTTCHER
Keyword(s):  
Background Radiation ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Emission Region ◽  
X Ray ◽  
Central Engine ◽  
Infrared Background ◽  
Very High Energy ◽  
Γ Ray

The BL Lac object 3C 66A was the target of an intensive multiwavelength monitoring campaign organized in 2003–2004. During the campaign, its spectral energy distribution (SED) was measured and flux measurements from radio to X-ray frequencies as well as upper limits in the very high energy (VHE) γ-ray regime were obtained. Here, we reproduce the SED and optical spectral variability pattern observed during our multiwavelength campaign using a time-dependent leptonic jet model. Our model could successfully simulate the observed SED and optical light curves and predict an intrinsic cutoff value for the VHE γ-ray emission at ~4 GeV implying the effect of the optical depth due to the intergalactic infrared background radiation (IIBR) to be negligible. Also, the contribution of external Comptonization (EIC), due to the presence of a broad-line region (BLR), in the emission of γ-ray photons could be significant early-on when the emission region is very close to the central engine but as it travels farther out, the production mechanism of hard X-ray and γ-ray photons becomes dominated by synchrotron self-Compton mechanism (SSC).

scholarly journals The flat-spectrum radio quasar 3C 345 from the high to the low emission state

2018 ◽  
Vol 614 ◽  
pp. A148 ◽  
Author(s):  
M. Berton ◽  
N. H. Liao ◽  
G. La Mura ◽  
E. Järvelä ◽  
E. Congiu ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Emission Lines ◽  
Spectral Energy ◽  
X Rays ◽  
Energy Bands ◽  
Line Region ◽  
Spectrum Radio ◽  
Inverse Compton ◽  
Public Archives ◽  
Radio Quasar

We report simultaneous observations at different energy bands in radio, optical, UV, X-rays and γ rays of the flat-spectrum radio-quasar 3C 345. We built the light curve of the source at different frequencies from 2008, the beginning of the Fermi all-sky survey, to 2016, using new data and public archives. In particular we obtained several optical spectra, to study the behavior of emission lines and the continuum in different activity states and to derive the black hole mass. 3C 345 showed two flaring episodes in 2009, which occurred simultaneously in γ ray, optical/UV and X-rays, and were later followed in radio. The source shows an inverse Compton dominated spectral energy distribution, which moved from higher to lower frequencies from the high to the low state. The reverberation of emission lines during one outburst event allowed us to constrain the location of production of γ rays very close to the broad-line region, and possibly in the jet-base. We report the observation of an increased accretion after the outburst, possibly induced by the decrease of magnetic field intensity with respect to the low state.

scholarly journals Advection-Dominated Accretion, Jets, and the Spectral Energy Distribution of LINERs

2009 ◽  
Vol 5 (S267) ◽  
pp. 313-318
Author(s):  
Rodrigo S. Nemmen ◽  
Thaisa Storchi-Bergmann ◽  
Michael Eracleous ◽  
Feng Yuan
Keyword(s):  
Mass Loss Rate ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Accretion Flow ◽  
Central Engine ◽  
Relativistic Jet ◽  
Recent Compilation ◽  
Accretion Physics

AbstractLow-luminosity active galactic nuclei (LLAGNs) represent the bulk of the AGN population in the present-day universe and they trace low-level accreting supermassive black holes. The observational properties of LLAGNs suggest that their central engines are intrinsically different from those of more luminous AGNs. It has been suggested that accretion in LLAGNs occurs via an advection-dominated accretion flow (ADAF) associated with strong jets. In order to probe the accretion physics in LLAGNs as a class, we model the multiwavelength spectral energy distributions (SEDs) of 24 LINERs (taken from a recent compilation by Eracleous et al.) with a coupled accretion-jet model. The accretion flow is modeled as an inner ADAF outside of which there is a truncated standard thin disk. These SEDs include radio, near-IR to near-UV HST data, and Chandra X-ray data. We find that the radio emission is severely underpredicted by ADAF models but can be explained by the relativistic jet. The origin of the X-ray radiation in most sources can be explained by three distinct scenarios: the X-rays can be dominated by emission from the ADAF, the jet, or from both components contributing at similar levels. From the model fits, we estimate important parameters of the central engine of LINERs, such as the mass accretion rate — relevant for studies of the feeding of AGNs — and the mass-loss rate in the jet and the jet power — relevant for studies of the kinetic feedback from jets.

scholarly journals A new hard X-ray-selected sample of extreme high-energy peaked BL Lac objects and their TeV gamma-ray properties

2019 ◽  
Vol 486 (2) ◽  
pp. 1741-1762 ◽  
Author(s):  
L Foffano ◽  
E Prandini ◽  
A Franceschini ◽  
S Paiano
Keyword(s):  
Spectral Properties ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac

ABSTRACT Extreme high-energy peaked BL Lac objects (EHBLs) are an emerging class of blazars with exceptional spectral properties. The non-thermal emission of the relativistic jet peaks in the spectral energy distribution (SED) plot with the synchrotron emission in X-rays and with the gamma-ray emission in the TeV range or above. These high photon energies may represent a challenge for the standard modelling of these sources. They are important for the implications on the indirect measurements of the extragalactic background light, the intergalactic magnetic field estimate, and the possible origin of extragalactic high-energy neutrinos. In this paper, we perform a comparative study of the multiwavelength spectra of 32 EHBL objects detected by the Swift-BAT telescope in the hard X-ray band and by the Fermi-LAT telescope in the high-energy gamma-ray band. The source sample presents uniform spectral properties in the broad-band SEDs, except for the TeV gamma-ray band where an interesting bimodality seems to emerge. This suggests that the EHBL class is not homogeneous, and a possible subclassification of the EHBLs may be unveiled. Furthermore, in order to increase the number of EHBLs and settle their statistics, we discuss the potential detectability of the 14 currently TeV gamma-ray undetected sources in our sample by the Cherenkov telescopes.

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