scholarly journals The challenging SED of AP Librae

2011 ◽  
Vol 7 (S284) ◽  
pp. 411-413 ◽  
Author(s):  
David Sanchez ◽  
Berrie Giebels ◽  
Pascal Fortin ◽  
Keyword(s):  
Spectral Energy Distribution ◽  
Broad Band ◽  
Low Frequency ◽  
Theoretical Models ◽  
Intermediate Frequency ◽  
High Energy ◽  
Spectral Energy ◽  
Broad Band Emission ◽  
Band Emission ◽  
Bl Lac

AbstractMatching the broad-band emission of active galaxies with the predictions of theoretical models can be used to derive constraints on the properties of the emitting region and to probe the physical processes involved. AP Librae is the third low frequency peaked BL Lac (LBL) detected at very high energy (VHE, E>100GeV) by an Atmospheric Cherenkov Telescope; most VHE BL Lacs (34 out of 39) belong to the high-frequency and intermediate-frequency BL Lac classes (HBL and IBL). LBL objects tend to have a higher luminosity with lower peak frequencies than HBLs or IBLs. The characterization of their time-averaged spectral energy distribution is challenging for emission models such as synchrotron self-Compton (SSC) models.

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 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.

scholarly journals Very High Energy gamma-rays from blazars

2013 ◽  
Vol 9 (S304) ◽  
pp. 119-124
Author(s):  
Helene Sol
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Low Frequency ◽  
High Energy ◽  
Spectral Energy ◽  
Bl Lac Objects ◽  
Cherenkov Telescopes ◽  
Bl Lac ◽  
Very High Energy ◽  
Very High

AbstractThe extragalactic very high energy (VHE) gamma-ray sky is dominated at the moment by more than fifty blazars detected by the present imaging atmospheric Cherenkov telescopes (IACT), with a majority (about 90%) of high-frequency peaked BL Lac objects (HBL) and a small number of low-frequency peaked and intermediate BL Lac objects (LBL and IBL) and flat spectrum radio quasars (FSRQ). A significant variability is often observed, with time scales from a few minutes to months and years. The spectral energy distribution (SED) of these blazars typically shows two bumps from the radio to the TeV range, which can usually be described by leptonic or hadronic processes. While elementary bricks of the VHE emission scenarios seem now reasonably well identified, a global picture of these sources, describing the geometry and dynamics of the VHE zone, is not yet available. Multiwavelength monitoring and global alert network will be important to better constrain the picture, especially with the perspective of CTA, a major project of the next generation in ground-based gamma-ray astronomy.

Microscintillator of Ce Doped β-NaLuF4 in Uniform Hexagonal Prism Morphology by a Facile Hydrothermal Method

2014 ◽  
Vol 541-542 ◽  
pp. 220-224
Author(s):  
Li Sha Liu ◽  
Hao Hong Chen ◽  
Bi Qiu Liu ◽  
Bin Tang ◽  
Zhi Jia Sun ◽  
...  
Keyword(s):  
Hydrothermal Method ◽  
Hexagonal Phase ◽  
Broad Band ◽  
High Energy ◽  
Hexagonal Prism ◽  
Facile Hydrothermal Method ◽  
X Ray ◽  
Strong Broad Band ◽  
Broad Band Emission ◽  
Band Emission

To explore micro-or nanoscintillator with a controllable architecture, a novel facile hydrothermal method easy for commercial run was used to synthesize pure and Ce doped β-NaLuF4 microcrystals at 453K. The morphology of uniform hexagonal prism with 3.3μm in diameter and 1.4 μm in thickness, respectively, is presented by the results of scanning electron microscopy (SEM). Powder X-ray diffraction (PXRD) patterns show the products are both pure hexagonal phase. Different from the undoped product without any irradiation, the Ce doped product has given strong broad band emission attributed to 5d4f transition of Ce3+, which can be potentially used as scintillator for biomedical imaging and detectors for high energy such as X-ray and γray. This synthetical strategy extends the understanding about nanomaterial chemistry and can be also useful for other systems such as fluorides, oxides and sulfides.

Synthesis, Characterization and Photophysical Properties of Rhenium(I) Complexe with 2-(naphthalen-2-yl)-1-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline

2014 ◽  
Vol 988 ◽  
pp. 66-69
Author(s):  
Qiang Li ◽  
Le Li ◽  
Rong Feng Zhong ◽  
Hai Di Cai ◽  
Feng Zhao
Keyword(s):  
Experimental Data ◽  
Solid State ◽  
Photophysical Properties ◽  
Broad Band ◽  
High Energy ◽  
H Nmr ◽  
Emission Maximum ◽  
Broad Band Emission ◽  
Band Emission

In this paper, a Re(I) complex [Re(CO)3(E2)Cl], where E2 = 2-(naphthalen-2-yl)-1-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline(E2), was synthesized and characterized by 1H NMR successfully. Experimental data confirm that Re(I) complex [Re(CO)3(E2)Cl] is high-energy-emitting one. The broad band emission upon excitation at λ = 400 nm with the emission maximum locates at λ = 581 nm in solid state and 614nm in CH2Cl2 solution were observed.

scholarly journals Constraining X-ray emission in HBL blazars using multiwavelength observations

2020 ◽  
Vol 496 (2) ◽  
pp. 1295-1306
Author(s):  
Alicja Wierzcholska ◽  
Stefan J Wagner
Keyword(s):  
Spectral Energy Distribution ◽  
Broad Band ◽  
Neutral Hydrogen ◽  
High Energy ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Additional Absorption ◽  
X Ray ◽  
Uv Excess ◽  
Survey Results

ABSTRACT The X-ray spectrum of extreme high-energy peaked BL Lac-type blazars is located in the synchrotron branch of the broad-band spectral energy distribution (SED), at energies below the peak. A joint fit of the extrapolated X-ray spectra together with a host galaxy template allows characterizing the synchrotron branch in the SED. The X-ray spectrum is usually characterized either with a pure or a curved power-law model. In the latter case, however, it is hard to distinguish an intrinsic curvature from excess absorption. In this paper, we focus on five well-observed blazars: 1ES 0229+200, PKS 0548−322, RX J 1136+6737, 1ES 1741+196, and 1ES 2344+514. We constrain the infrared to X-ray emission of these five blazars using a model that is characterized by the host galaxy, spectral curvature, absorption, and ultraviolet (UV) excess to separate these spectral features. In the case of four sources, namely 1ES 0229+200, PKS 0548−322, 1ES 1741+196, and 1ES 2344+514, the spectral fit with the atomic neutral hydrogen from the Leiden Argentina Bonn Survey results in a significant UV excess present in the broad-band SED. Such excess can be interpreted as an additional component, for example, a blue bump. However, in order to describe spectra of these blazars without such excess, additional absorption to the atomic neutral hydrogen from the Leiden Argentina Bonn Survey is needed.

scholarly journals Extreme and high synchrotron peak blazars beyond 4FGL: The 2BIGB γ-ray catalogue

2020 ◽  
Vol 493 (2) ◽  
pp. 2438-2451
Author(s):  
B Arsioli ◽  
Y-L Chang ◽  
B Musiimenta
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
Data Repositories ◽  
Total Contribution ◽  
Public Data ◽  
Γ Ray

ABSTRACT This paper presents the results of a γ-ray likelihood analysis over all the extreme and high synchrotron peak blazars (EHSP and HSP) from the 3HSP catalogue. We investigate 2013 multifrequency positions under the eyes of Fermi Large Area Telescope, considering 11 yr of observations in the energy range between 500 MeV and 500 GeV, which results in 1160 γ-ray signatures detected down to the TS=9 threshold. The detections include 235 additional sources concerning the Fermi Large Area Telescope Fourth Source Catalog (4FGL), all confirmed via high-energy TS (Test Statistic) maps, and represent an improvement of ∼25 per cent for the number of EHSP and HSP currently described in γ-rays. We build the γ-ray spectral energy distribution (SED) for all the 1160 2BIGB sources, plot the corresponding γ-ray logN−logS, and measure their total contribution to the extragalactic gamma-ray background, which reaches up to ∼33 per cent at 100 GeV. Also, we show that the γ-ray detectability improves according to the synchrotron peak flux as represented by the figure of merit parameter, and note that the search for TeV peaked blazars may benefit from considering HSP and EHSP as a whole, instead of EHSPs only. The 2BIGB acronym stands for ‘Second Brazil-ICRANet Gamma-ray Blazars’ catalogue, and all the broad-band models and SED data points will be available on public data repositories (OpenUniverse, GitHub, and Brazilian Science Data Center-BSDC).

scholarly journals Long term γ-ray variability of blazars

2020 ◽  
Vol 634 ◽  
pp. A80 ◽  
Author(s):  
Bhoomika Rajput ◽  
C. S. Stalin ◽  
Suvendu Rakshit
Keyword(s):  
Time Scales ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
Bl Lac Objects ◽  
Spectrum Radio ◽  
Bl Lac ◽  
Bl Lacs

We used the data from the Fermi Gamma-ray Space Telescope to characterise the γ-ray flux variability of blazars on month-like time scales. Our sample consists of 1120 blazars of which 481 are flat spectrum radio quasars (FSRQs) and 639 are BL Lac objects (BL Lacs). We generated monthly binned light curves of our sample for a period of approximately nine years from 2008 August to 2017 December and quantified variability by using excess variance (Fvar). On month-like time scales, 371/481 FSRQs are variable (80%), while only about 50% (304/639) of BL Lacs are variable. This suggests that FSRQs are more variable than BL Lac objects. We find a mean Fvar of 0.55 ± 0.33 and 0.47 ± 0.29 for FSRQs and BL Lacs respectively. Large Fvar in FSRQs is also confirmed from the analysis of the ensemble structure function. By Dividing our sample of blazars based on the position of the synchrotron peak in their broad-band spectral energy distribution, we find that the low synchrotron peaked (LSP) sources have the largest mean Fvar value of 0.54 ± 0.32 while the intermediate synchrotron peaked (ISP) and high synchrotron peaked sources have mean Fvar values of 0.45 ± 0.25 and 0.47 ± 0.33 respectively. On month-like time scales, we find FSRQs to show a high duty cycle (DC) of variability of 66% relative to BL Lacs that show a DC of 36%. We find that both the Fvar and time scale of variability (τ) do not correlate with MBH. We note that Fvar is found to be weakly correlated with Doppler factor (δ) and τ is also weakly correlated with δ. Most of the sources in our sample have τ of the order of days, which might be related to processes in the jet. We find marginal difference in the distribution of τ between FSRQs and BL Lacs.

Synthesis, Characterization and Photophysical Properties of a New CuI Complexe Contain Bis[2-(diphenylphosphino)phenyl]ether and 2-(anthracen-9-yl)-1-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline

2014 ◽  
Vol 1033-1034 ◽  
pp. 1163-1166
Author(s):  
Ji Ling He
Keyword(s):  
Experimental Data ◽  
Photophysical Properties ◽  
Broad Band ◽  
High Energy ◽  
Phenyl Ether ◽  
H Nmr ◽  
Emission Maximum ◽  
Broad Band Emission ◽  
Band Emission ◽  
Diimine Ligand

In this paper, a new diimine ligand of 2-(anthracen-9-yl)-1-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline(D1) and its corresponding CuI complex contain Bis[2-(diphenylphosphino)phenyl]ether were synthesized and characterized by 1H NMR successfully. Experimental data confirm that Complex [Cu(D1)(DPEphos)](PF6) is high-energy-emitting one. The broad band emission upon excitation at λ = 400 nm with the emission maximum locates at λ = 579 nm was observed. This makes them potential candidates as cheap emitting materials.

Synthesis, Characterization and Photophysical Properties of a New CuI Complexe Contain Bis[2-(diphenylphosphino)phenyl] ether and 7,10-Dimethyl Pyrazino [2,3-f][1,10]phenanthroline

2014 ◽  
Vol 941-944 ◽  
pp. 610-613
Author(s):  
Qiang Li ◽  
Zhenh Xiong ◽  
Rongf Zhong ◽  
Feng Zhao
Keyword(s):  
Experimental Data ◽  
1H Nmr ◽  
Photophysical Properties ◽  
Broad Band ◽  
High Energy ◽  
Red Shift ◽  
Phenyl Ether ◽  
Emission Maximum ◽  
Broad Band Emission ◽  
Band Emission

In this paper, a new CuI complex containing the bis[2-(diphenylphosphino)phenyl]ether and 7,10-Dimethyl Pyrazino [2,3-f][1,10]phenanthroline have been syntheized and characterized by 1H NMR successfully. Experimental data confirm that Complex [Cu(dppl)(DPEphos)](PF6) is high-energy-emitting one. The broad band emission upon excitation at λ = 420 nm with the emission maximum locates at λ = 577 nm was observed. The introduction of DPEphos system leads to red shift of emissive about 11 nm than complex [Cu(dppl)2](PF6). This makes them potential candidates as cheap emitting materials.

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