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 An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state

2020 ◽  
Vol 496 (3) ◽  
pp. 3912-3928
Author(s):  
MAGIC Collaboration: V A Acciari ◽  
S Ansoldi ◽  
L A Antonelli ◽  
A Arbet Engels ◽  
A Babić ◽  
...  
Keyword(s):  
Crab Nebula ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Bl Lac ◽  
Very High Energy ◽  
Γ Ray ◽  
Using Data ◽  
The Crab Nebula

ABSTRACT Extreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at νs ≥ 1017 Hz. The BL Lac object 1ES 2344+514 was included in the EHBL family because of its impressive shift of the synchrotron peak in 1996. During the following years, the source appeared to be in a low state without showing any extreme behaviours. In 2016 August, 1ES 2344+514 was detected with the ground-based γ-ray telescope FACT during a high γ-ray state, triggering multiwavelength (MWL) observations. We studied the MWL light curves of 1ES 2344+514 during the 2016 flaring state, using data from radio to very-high-energy (VHE) γ-rays taken with OVRO, KAIT, KVA, NOT, some telescopes of the GASP-WEBT collaboration at the Teide, Crimean, and St. Petersburg observatories, Swift-UVOT, Swift-XRT, Fermi-LAT, FACT, and MAGIC. With simultaneous observations of the flare, we built the broad-band SED and studied it in the framework of a leptonic and a hadronic model. The VHE γ-ray observations show a flux level of 55 per cent of the Crab Nebula flux above 300 GeV, similar to the historical maximum of 1995. The combination of MAGIC and Fermi-LAT spectra provides an unprecedented characterization of the inverse-Compton peak for this object during a flaring episode. The Γ index of the intrinsic spectrum in the VHE γ-ray band is 2.04 ± 0.12stat ± 0.15sys. We find the source in an extreme state with a shift of the position of the synchrotron peak to frequencies above or equal to 1018 Hz.

scholarly journals Non-thermal emission in radio galaxy lobes – II. Centaurus A, Centaurus B, and NGC 6251

2019 ◽  
Vol 490 (2) ◽  
pp. 1489-1497 ◽  
Author(s):  
Massimo Persic ◽  
Yoel Rephaeli
Keyword(s):  
Thermal Emission ◽  
Background Radiation ◽  
Spectral Energy Distribution ◽  
Recent Analysis ◽  
Spectral Energy ◽  
Energetic Proton ◽  
X Ray ◽  
Radiation Fields ◽  
Γ Ray ◽  
Centaurus A

ABSTRACT Radio and γ-ray measurements of large lobes of several radio galaxies provide adequate basis for determining whether emission in these widely separated spectral regions is largely by energetic electrons. This is very much of interest as there is of yet no unequivocal evidence for a significant energetic proton component to account for γ-ray emission by neutral pion decay. A quantitative assessment of the pion yield spectral distribution necessitates full accounting of the local and background radiation fields in the lobes; indeed, doing so in our recent analysis of the spectral energy distribution of the Fornax A lobes considerably weakened previous conclusions on the hadronic origin of the emission measured by the Fermi satellite. We present the results of similar analyses of the measured radio, X-ray, and γ-ray emission from the lobes of Centaurus A, Centaurus B, and NGC 6251. The results indicate that the measured γ-ray emission from these lobes can be accounted for by Compton scattering of the radio-emitting electrons off the superposed radiation fields in the lobes; consequently, we set upper bounds on the energetic proton contents of the lobes.

scholarly journals Tracing the high energy emission of γ-ray detected radio loud quasars

2014 ◽  
Vol 10 (S313) ◽  
pp. 225-230
Author(s):  
Giulia Migliori
Keyword(s):  
Spectral Energy Distribution ◽  
High Energy ◽  
Host Galaxy ◽  
Spectral Energy ◽  
X Ray ◽  
Relativistic Jet ◽  
Quasar Jets ◽  
Γ Ray ◽  
High Energy Emission ◽  
Jet Power

AbstractWe present a multiwavelength study of the core and relativistic jet of the radio loud (RL) quasar RGB J1512+020A (z=0.20). We report the discovery of a bright, 13” extended X-ray jet with a short Chandra observation. We discuss the origin of the jet X-ray emission and its properties in comparison with sample of X-ray quasar jets. The broadband core spectrum is contributed by the emission of the central quasar, by a blazar component, responsible for the γ-ray emission detected by Fermi, and by the host galaxy. We model the non-thermal blazar spectral energy distribution (SED) and constrain the total jet power. The jet power inferred from the blazar SED modeling is in agreement with the values obtained from the total radio power, pointing to a jet that efficiently carries its power up to kiloparsec scales. The quasar emission appears intrinsically weak in the optical-UV band. The disk luminosity estimated from the broad emission lines is lower than the jet power, in agreement with recent results from observations and theory.

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 Detection of persistent VHE gamma-ray emission from PKS 1510–089 by the MAGIC telescopes during low states between 2012 and 2017

2018 ◽  
Vol 619 ◽  
pp. A159 ◽  
Author(s):  
◽  
V. A. Acciari ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
A. Arbet Engels ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Outer Radius ◽  
Spectral Energy ◽  
Emission Region ◽  
Emission Model ◽  
Broadband Emission ◽  
Very High Energy ◽  
Gamma Ray Emission

Context. PKS 1510–089 is a flat spectrum radio quasar strongly variable in the optical and GeV range. To date, very high-energy (VHE, > 100 GeV) emission has been observed from this source either during long high states of optical and GeV activity or during short flares. Aims. We search for low-state VHE gamma-ray emission from PKS 1510–089. We characterize and model the source in a broadband context, which would provide a baseline over which high states and flares could be better understood. Methods. PKS 1510–089 has been monitored by the MAGIC telescopes since 2012. We use daily binned Fermi-LAT flux measurements of PKS 1510–089 to characterize the GeV emission and select the observation periods of MAGIC during low state of activity. For the selected times we compute the average radio, IR, optical, UV, X-ray, and gamma-ray emission to construct a low-state spectral energy distribution of the source. The broadband emission is modeled within an external Compton scenario with a stationary emission region through which plasma and magnetic fields are flowing. We also perform the emission-model-independent calculations of the maximum absorption in the broad line region (BLR) using two different models. Results. The MAGIC telescopes collected 75 hr of data during times when the Fermi-LAT flux measured above 1 GeV was below 3  ×  10−8 cm−2 s−1, which is the threshold adopted for the definition of a low gamma-ray activity state. The data show a strongly significant (9.5σ) VHE gamma-ray emission at the level of (4.27 ± 0.61stat)  ×  10−12 cm−2 s−1 above 150 GeV, a factor of 80 lower than the highest flare observed so far from this object. Despite the lower flux, the spectral shape is consistent with earlier detections in the VHE band. The broadband emission is compatible with the external Compton scenario assuming a large emission region located beyond the BLR. For the first time the gamma-ray data allow us to place a limit on the location of the emission region during a low gamma-ray state of a FSRQ. For the used model of the BLR, the 95% confidence level on the location of the emission region allows us to place it at a distance > 74% of the outer radius of the BLR.

scholarly journals VERY-HIGH ENERGY PROCESSES IN BLACK HOLE MAGNETOSPHERE: THE CASE OF M87

2014 ◽  
Vol 28 ◽  
pp. 1460189 ◽  
Author(s):  
STEPHANE VINCENT
Keyword(s):  
Black Hole ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Morphological Studies ◽  
Very High Energy ◽  
Γ Rays ◽  
Γ Ray ◽  
Energy Processes ◽  
Very High

M87 is a nearby radio galaxy that is detected at energies ranging from radio to very high energy (VHE) γ-rays. Its proximity and its jet, misaligned from our line of sight, enable detailed morphological studies. The detection of rapidly variable TeV emissions on timescale of ~ 1 day implies a source of a few Schwarzschild radii R Sch . The γ-ray telescopes cannot provide images with a sufficient resolution to localize the sites of the γ-ray production. However, both X-ray and radio observations have shown evidence that charged particles are accelerated in the immediate vicinity of the black hole closer than 100 R Sch . We propose that the non-thermal particle acceleration and the VHE emission processes may occur in a pair-starved region of the black hole (BH) magnetosphere. We produce a broadband spectral energy distribution (SED) of the resulting radiation and compare the model with the observed fluxes from the nucleus of M87 for the high γ-ray activities.

scholarly journals TeV Gamma–Ray Absorption and the Intergalactic Infrared Background

2001 ◽  
Vol 204 ◽  
pp. 135-149 ◽  
Author(s):  
F. W. Stecker
Keyword(s):  
Gamma Ray ◽  
Lorentz Invariance ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
High Energy ◽  
Spectral Energy ◽  
Empirical Modelling ◽  
Infrared Spectral ◽  
Infrared Background ◽  
Γ Ray

In this paper, I will take a synoptic approach to determining the intergalactic infrared radiation field (IIRF). This approach draws on both the multi-TeV γ-ray observations and the infrared background observations and relates them via the semi-empirical modelling method of Malkan & Stecker. I discuss the evidence for an intergalactic infrared background obtained by an analysis of the HEGRA observations of the high energy γ-ray spectrum of Mrk 501 and from constraints from Mrk 421 deduced from the Whipple air Cherenkov telescope results. I will show that this evidence is in accord with the predictions made by Malkan & Stecker (1998) for the intergalactic infrared spectral energy distribution produced by galaxies. The Malkan-Stecker predictions are also in excellent agreement with mid-infrared galaxy counts. However, there may be potential problems relating these predictions with the results of the analysis of COBE–DIRBE far infrared data. The γ-ray and COBE–DIRBE observations may also need to be reconciled. I will discuss possible ways to resolve this situation including a partial nullification of the γ-ray absorption process which can hypothetically occur if Lorentz invariance is broken.

scholarly journals Multiwavelength study of high-redshift blazars

2020 ◽  
Vol 498 (2) ◽  
pp. 2594-2613
Author(s):  
N Sahakyan ◽  
D Israyelyan ◽  
G Harutyunyan ◽  
M Khachatryan ◽  
S Gasparyan
Keyword(s):  
High Redshift ◽  
High Energy ◽  
Spectral Energy ◽  
Emission Region ◽  
Optical Telescope ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Temporal Properties ◽  
Uv Excess ◽  
Γ Ray

ABSTRACT High-redshift blazars are among the most powerful objects in the Universe. The spectral and temporal properties of 33 distant blazars (z > 2.5) detected in the high-energy γ-ray band are investigated by analysing the Fermi-LAT and Swift Ultraviolet and Optical Telescope/X-ray Telescope (UVOT/XRT) data. The considered sources have soft time-averaged γ-ray spectra (Γγ ≥ 2.2) whereas those that have been observed in the X-ray band have hard X-ray spectra (ΓX = 1.01−1.86). The γ-ray flux of high-redshift blazars ranges from 4.84 × 10−10 to 1.50 × 10−7 photon cm−2 s−1 and the luminosity is within (0.10−5.54) × 1048 erg s−1 which during the γ-ray flares increases up to (0.1−1) × 1050 erg s−1. In the X-ray band, only the emission of PKS 0438−43, B2 0743+25, and TXS 0222+185 is found to vary in different Swift XRT observations whereas in the γ-ray band, the emission is variable for fourteen sources: the flux of B3 1343+451 and PKS 0537−286 changes in sub-day scales, that of PKS 0347−211 and PKS 0451−28 in day scales, while the γ-ray variability of the others is in week or month scales. The properties of distant blazar jets are derived by modelling the multiwavelength spectral energy distributions within a one-zone leptonic scenario assuming that the X-ray and γ-ray emissions are produced from inverse Compton scattering of synchrotron and dusty torus photons. From the fitting, the emission region size is found to be ≤0.05 pc and the magnetic field and the Doppler factor are correspondingly within 0.10−1.74 G and 10.0−27.4. By modelling the optical–UV excess, we found that the central black hole masses and accretion disc luminosities are within Ld ≃ (1.09−10.94) × 1046 erg s−1 and (1.69−5.35) × 109 M⊙, respectively.

Exploring the radio and GeV-TeV γ-ray connection in the different blazar sub-classes

2018 ◽  
Vol 14 (S342) ◽  
pp. 180-183
Author(s):  
R. Lico ◽  
M. Giroletti ◽  
M. Orienti ◽  
L. Costamante ◽  
V. Pavlidou ◽  
...  
Keyword(s):  
Radio Emission ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Essential Step ◽  
Very High Energy ◽  
Γ Rays ◽  
Γ Ray ◽  
High Energy Emission ◽  
Very High

AbstractAs revealed by the Fermi-LAT, blazars represent the dominant population of γ-ray emitters. An essential step for understanding blazar physics and the emission mechanisms is the investigation of a possible connection between the observed low- and high-energy emission. A number of works report on the existence of a significant correlation between radio emission and 0.1-100 GeV γ rays. How does this correlation evolve when very high energy (VHE, E > 0.1 TeV) γ rays are considered? The possible radio-VHE emission connection is still elusive mainly because of the lack of a homogeneous VHE sky coverage. In this work we explore the connection between the parsec-scale radio emission and GeV-TeV γ rays by using two unbiased blazar samples extracted from the 1FHL ( E > 10 GeV) and 2FHL (E > 50 GeV) Fermi catalogs. For comparison, we perform the same analysis by using the 3FGL 0.1-300 GeV γ-ray energy flux. Overall, we find out that there is no significant connection between radio and γ-ray emission above 10 GeV for all the blazar sub-classes with the exception of high synchrotron peaked objects. Conversely, when 0.1-300 GeV γ-ray energies are considered, a strong and significant correlation is found for all of the blazar sub-classes. We interpret these results within the context of the blazar spectral energy distribution properties.

scholarly journals The TeV-emitting radio galaxy 3C 264

2019 ◽  
Vol 627 ◽  
pp. A89 ◽  
Author(s):  
B. Boccardi ◽  
G. Migliori ◽  
P. Grandi ◽  
E. Torresi ◽  
F. Mertens ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Physical Parameters ◽  
Data Set ◽  
X Ray ◽  
The Core ◽  
Very High Energy ◽  
Acceleration Zone

Context.In March 2018, the detection by VERITAS of very-high-energy emission (VHE >  100 GeV) from 3C 264 was reported. This is the sixth, and second most distant, radio galaxy ever detected in the TeV regime.Aims.In this article we present a radio and X-ray analysis of the jet in 3C 264. We determine the main physical parameters of the parsec-scale flow and explore the implications of the inferred kinematic structure for radiative models of thisγ-ray emitting jet.Methods.The radio data set is comprised of VLBI observations at 15 GHz from the MOJAVE program, and covers a time period of about two years. Through a segmented wavelet decomposition method (WISE code), we estimated the apparent displacement of individual plasma features; we then performed a pixel-based analysis of the stacked image to determine the jet shape. The X-ray data set includes all available observations from theChandra, XMM, andSwiftsatellites, and is used, together with archival data in the other bands, to build the spectral energy distribution (SED).Results.Proper motion is mostly detected along the edges of the flow, which appears strongly limb brightened. The apparent speeds increase as a function of distance from the core up to a maximum of ∼11.5 c. This constrains the jet viewing angle to assume relatively small values (θ ≲ 10°). In the acceleration region, extending up to a de-projected distance of ∼4.8 × 104Schwarzschild radii (∼11 pc), the jet is collimating (r ∝ z0.40 ± 0.04), as predicted for a magnetically-driven plasma flow. By assuming that the core region is indeed magnetically dominated (UB/Ue >  1), the SED and the jet power can be well reproduced in the framework of leptonic models, provided that the high-energy component is associated to a second emitting region. The possibility that this region is located at the end of the acceleration zone, either in the jet layer or in the spine, is explored in the modeling.

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