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 Fermi LAT detection of the supernova remnant SN 1006 revisited: The southwest limb

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Yi Xing ◽  
Zhongxiang Wang ◽  
Xiao Zhang ◽  
Yang Chen
Keyword(s):  
Supernova Remnant ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
Significance Level ◽  
Very High Energy ◽  
Γ Ray ◽  
Energy Emissions

Abstract The data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have recently been updated. Thus we re-analyze the LAT data for the supernova remnant (SNR) SN 1006. Two parts of γ-ray emission from the region are clearly resolved, which correspond to the northeast (NE) and southwest (SW) limbs of the SNR. The former has been detected in the previous LAT data (Xing et al. 2016, ApJ, 823, 44), but the latter is newly detected in this work. The detections of the two limbs are at a ∼4σ significance level, and the spectral results for the NE limb are consistent with those obtained in previous detection analyses. We construct the broadband spectral energy distribution (SED) for the SW limb. Different scenarios are considered for its SED in γ-ray energies. We conclude that, very similarly in the case of the NE limb, the high-energy and very high-energy emissions from the SW limb is likely dominated by the leptonic process, in which high-energy electrons accelerated from the shell region of the SNR inverse-Compton scatter background photons to γ-rays.

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 Detection of a flaring blazar coincident with an IceCube high-energy neutrino

2019 ◽  
Vol 207 ◽  
pp. 02001
Author(s):  
Anna Franckowiak
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Neutrino Flux ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
High Energy Neutrino ◽  
Energy Neutrino ◽  
Radio Wavelength ◽  
First Time

In September 22, 2017, IceCube released a public alert announcing the detection of a 290 TeV neutrino track event with an angular uncertainty of one square degree (90% containment). A multi-messenger follow-up campaign was initiated resulting in the detection of a GeV gamma-ray flare by the Fermi Large Area Telescope positionally consistent with the location of the known Bl Lac object, TXS 0506+056 , located only 0.1 degrees from the best-fit neutrino position. The probability of finding a GeV gamma-ray flare in coincidence with a high-energy neutrino event assuming a correlation of the neutrino flux with the gamma-ray energy flux in the energy band between 1 and 100 GeV was calculated to be 3σ (after trials correction). Following the detection of the flaring blazar the imaging air Cherenkov telescope MAGIC detected the source for the first time in the > 100 GeV gamma-ray band. The activity of the source was confirmed in X-ray, optical and radio wavelength. Several groups have developed lepto-hadronic models which succeed to explain the multi-messenger spectral energy distribution.

scholarly journals High-energy emission from galaxies: the star-formation/gamma-ray connection

2011 ◽  
Vol 7 (S284) ◽  
pp. 382-388
Author(s):  
Stefan Ohm ◽  
Jim Hinton
Keyword(s):  
Particle Acceleration ◽  
Star Formation ◽  
Gamma Ray ◽  
Broad Band ◽  
High Energy ◽  
High Mass ◽  
Spectral Energy ◽  
Mass Star ◽  
Γ Ray ◽  
The Impact

AbstractThe impact of non-thermal processes on the spectral energy distributions of galaxies can be dramatic, but such processes are often neglected in considerations of their structure and evolution. Particle acceleration associated with high mass star formation and AGN activity not only leads to very broad band (radio-γ-ray) emission, but may also produce very significant feedback effects on galaxies and their environment. The recent detections of starburst galaxies at GeV and TeV energies suggest that γ-ray instruments have now reached the critical level of sensitivity to probe the connection between particle acceleration and star-formation in galaxies. In this paper we will try to summarise this recent progress, put it into a multi-wavelength context and also discuss the prospects for more precise and sensitive γ-ray measurements with the upcoming CTA observatory.

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.

Multiwavelength study of different flaring and low-activity states of blazar 4C+21.35

2020 ◽  
Vol 500 (1) ◽  
pp. 1127-1138
Author(s):  
Debbijoy Bhattacharya ◽  
Krishna Mohana A ◽  
Subir Bhattacharyya ◽  
Nilay Bhatt ◽  
C S Stalin
Keyword(s):  
Spectral Energy Distribution ◽  
Broad Band ◽  
Optical Data ◽  
Spectral Energy ◽  
Emission Region ◽  
Electromagnetic Spectrum ◽  
Large Area ◽  
Γ Ray ◽  
The One ◽  
Low Activity

ABSTRACT Blazars, a class of active galactic nuclei, emit over the entire accessible electromagnetic spectrum and modelling of their broad-band spectral energy distribution (SED) is the key to constrain the underlying emission mechanisms. Here we report the results on the one-zone leptonic emission modelling carried out on the blazar 4C+21.35 using multiwavelength data spanning over the period 2008–2018. Broad-band SED modelling using γ-ray data from Fermi-Large Area Telescope, X-ray data from Swift-XRT and AstroSat, and UV–optical data from Swift-UVOT, AstroSat, and Catalina Real-Time Transient Survey was carried out at seven different epochs, including three γ-ray flaring episodes and four quiescent periods (three long-term averaged ones and one during AstroSat observing period). Our SED modelling suggests that two compact emission regions originating at a different time outside the broad-line region and moving away from the core with variation primarily in the jet electron spectra can explain the emission from the high-, moderate-, and low-activity periods. The emissions from high- and first low-activity states are likely to have originated in the first region. The moderate- and second low-activity states are likely due to the second emission region with fresh particle acceleration/injection at a later time.

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 Testing emission models on the extreme blazar 2WHSP J073326.7+515354 detected at very high energies with the MAGIC telescopes

2019 ◽  
Vol 490 (2) ◽  
pp. 2284-2299 ◽  
Author(s):  
◽  
◽  
V A Acciari ◽  
S Ansoldi ◽  
L A Antonelli ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Physical Nature ◽  
High Energy ◽  
Spectral Energy ◽  
Emission Model ◽  
Theoretical Frameworks ◽  
Spectral Parameters ◽  
Bl Lac Objects

ABSTRACT Extreme high-energy-peaked BL Lac objects (EHBLs) are an emerging class of blazars. Their typical two-hump-structured spectral energy distribution (SED) peaks at higher energies with respect to conventional blazars. Multiwavelength (MWL) observations constrain their synchrotron peak in the medium to hard X-ray band. Their gamma-ray SED peaks above the GeV band, and in some objects it extends up to several TeV. Up to now, only a few EHBLs have been detected in the TeV gamma-ray range. In this paper, we report the detection of the EHBL 2WHSP J073326.7+515354, observed and detected during 2018 in TeV gamma rays with the MAGIC telescopes. The broad-band SED is studied within an MWL context, including an analysis of the Fermi-LAT data over 10 yr of observation and with simultaneous Swift-XRT, Swift-UVOT, and KVA data. Our analysis results in a set of spectral parameters that confirms the classification of the source as an EHBL. In order to investigate the physical nature of this extreme emission, different theoretical frameworks were tested to model the broad-band SED. The hard TeV spectrum of 2WHSP J073326.7+515354 sets the SED far from the energy equipartition regime in the standard one-zone leptonic scenario of blazar emission. Conversely, more complex models of the jet, represented by either a two-zone spine-layer model or a hadronic emission model, better represent the broad-band SED.

scholarly journals Correlation between optical and γ-ray flux variations in bright flat spectrum radio quasars

2020 ◽  
Vol 498 (4) ◽  
pp. 5128-5148
Author(s):  
Bhoomika Rajput ◽  
C S Stalin ◽  
S Sahayanathan
Keyword(s):  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Light Curves ◽  
Spectral Energy ◽  
Emission Model ◽  
Uv Emission ◽  
Spectrum Radio ◽  
Cross Correlation Analysis ◽  
Γ Ray

ABSTRACT Blazars are known to show flux variations over a range of energies from low-energy radio to high-energy γ-rays. Cross-correlation analysis of the optical and γ-ray light curves in blazars shows that flux variations are generally correlated in both bands, however, there are exceptions. We explored this optical–GeV connection in four flat spectrum radio quasars by a systematic investigation of their long-term optical and γ-ray light curves. On analysis of the four sources, namely 3C 273, 3C 279, PKS 1510−089, and CTA 102, we noticed different behaviours between the optical and GeV flux variations. We found instances when (i) the optical and GeV flux variations are closely correlated, (ii) there are optical flares without γ-ray counterparts, and (iii) γ-ray flares without optical counterparts. To understand these diverse behaviours, we carried out broad-band spectral energy distribution (SED) modelling of the sources at different epochs using a one-zone leptonic emission model. The optical–UV emission is found to be dominated by emission from the accretion disc in the sources PKS 1510−089, CTA 102, and 3C 273, while in 3C 279, the synchrotron radiation from the jet dominates the optical–UV emission. Our SED analysis indicates that (i) correlated optical and γ-ray flux variations are caused by changes in the bulk Lorentz factor (Γ), (ii) γ-ray flares without optical counterparts are due to increase in Γ and/or the electron energy density, and (iii) an optical flare without γ-ray counterpart is due to increase in the magnetic field strength.

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.

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