scholarly journals SPECTROSCOPY OF OPTICALLY SELECTED BL LAC OBJECTS AND THEIR γ-RAY EMISSION

2013 ◽  
Vol 146 (6) ◽  
pp. 163 ◽  
Author(s):  
A. Sandrinelli ◽  
A. Treves ◽  
R. Falomo ◽  
E. P. Farina ◽  
L. Foschini ◽  
...  
Keyword(s):  
Bl Lac Objects ◽  
Bl Lac ◽  
Γ Ray

scholarly journals Gamma-ray counterparts of 2WHSP high-synchrotron-peaked BL Lac objects as possible signatures of ultra-high-energy cosmic ray emission

2020 ◽  
Vol 497 (2) ◽  
pp. 2455-2468
Author(s):  
Michael W Toomey ◽  
Foteini Oikonomou ◽  
Kohta Murase
Keyword(s):  
Energy Range ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
High Energy ◽  
Potential Candidate ◽  
Ultra High Energy ◽  
Bl Lac Objects ◽  
Cherenkov Telescopes ◽  
Bl Lac ◽  
Γ Ray

ABSTRACT We present a search for high-energy γ-ray emission from 566 Active Galactic Nuclei at redshift z > 0.2, from the 2WHSP catalogue of high-synchrotron peaked BL Lac objects with 8 yr of Fermi-LAT data. We focus on a redshift range where electromagnetic cascade emission induced by ultra-high-energy cosmic rays can be distinguished from leptonic emission based on the spectral properties of the sources. Our analysis leads to the detection of 160 sources above ≈5σ (TS ≥25) in the 1–300 GeV energy range. By discriminating significant sources based on their γ-ray fluxes, variability properties, and photon index in the Fermi-LAT energy range, and modelling the expected hadronic signal in the TeV regime, we select a list of promising sources as potential candidate ultra-high-energy cosmic ray emitters for follow-up observations by Imaging Atmospheric Cherenkov Telescopes.

Gamma-ray Emission from the γ-ray-loud BL Lac Objects

2001 ◽  
Vol 1 (6) ◽  
pp. 494-500 ◽  
Author(s):  
Guang-Zhong Xie ◽  
Ben-Zhong Dai ◽  
En-Wei Liang ◽  
Zhao-Hua Xie
Keyword(s):  
Gamma Ray ◽  
Bl Lac Objects ◽  
Bl Lac ◽  
Γ Ray ◽  
Gamma Ray Emission

scholarly journals Very high energy γ-ray emission from two blazars of unknown redshift and upper limits on their distance

2020 ◽  
Vol 494 (4) ◽  
pp. 5590-5602
Author(s):  
H Abdalla ◽  
R Adam ◽  
F Aharonian ◽  
F Ait Benkhali ◽  
E O Angüner ◽  
...  
Keyword(s):  
Confidence Level ◽  
High Energy ◽  
Bl Lac Objects ◽  
Upper Limit ◽  
Upper Limits ◽  
Bl Lac ◽  
Very High Energy ◽  
Stereoscopic System ◽  
Γ Ray ◽  
Very High

ABSTRACT We report on the detection of very high energy (VHE; E > 100 GeV) γ-ray emission from the BL Lac objects KUV 00311−1938 and PKS 1440−389 with the High Energy Stereoscopic System (H.E.S.S.). H.E.S.S. observations were accompanied or preceded by multiwavelength observations with Fermi/LAT, XRT and UVOT onboard the Swift satellite, and ATOM. Based on an extrapolation of the Fermi/LAT spectrum towards the VHE γ-ray regime, we deduce a 95 per cent confidence level upper limit on the unknown redshift of KUV 00311−1938 of $z$ < 0.98 and of PKS 1440−389 of $z$ < 0.53. When combined with previous spectroscopy results, the redshift of KUV 00311−1938 is constrained to 0.51 ≤ $z$ < 0.98 and of PKS 1440−389 to 0.14 ⪅ $z$ < 0.53.

scholarly journals DIFFUSE γ-RAY EMISSION FROM UNRESOLVED BL LAC OBJECTS

2014 ◽  
Vol 786 (2) ◽  
pp. 129 ◽  
Author(s):  
M. Di Mauro ◽  
F. Donato ◽  
G. Lamanna ◽  
D. A. Sanchez ◽  
P. D. Serpico
Keyword(s):  
Bl Lac Objects ◽  
Bl Lac ◽  
Γ Ray

A Study of the γ-ray and X-ray Radiations of BL Lac Objects

2009 ◽  
Vol 33 (1) ◽  
pp. 17-24
Author(s):  
Hao-jing Zhang ◽  
Xiong Zhang
Keyword(s):  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Γ Ray

MODELING OF NON-HBL VHE γ-RAY BLAZARS

2009 ◽  
Vol 18 (10) ◽  
pp. 1517-1521
Author(s):  
MARKUS BÖTTCHER
Keyword(s):  
High Energy ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Bl Lac Objects ◽  
Spectrum Radio ◽  
Bl Lac ◽  
Γ Ray ◽  
High Energy Emission ◽  
Radio Quasar ◽  
Negligible Contribution

This is a summary of recent modeling results of three newly detected TeV blazars of the intermediate BL Lac object (IBL) and flat-spectrum radio quasar (FSRQ) sub-classes: W Comae, 3C 66A, and 3C 279. For model fits to the spectral energy distributions of W Comae and 3C 66A, a non-negligible contribution from a source of soft radiation external to the jets of these blazars is strongly preferred over pure synchrotron-self-Compton or synchrotron-proton-blazar models, respectively. This indicates that IBLs are truly intermediate between the "classical" TeV blazars (high-frequency-peaked BL Lac objects) and FSRQs. The VHE γ-ray detection of the FSRQ 3C 279 poses severe challenges for leptonic models, and seems to favor a hadronic origin of the high-energy emission. However, even a hadronic model suffers from problems with extreme energy requirements.

The X-∕VHE γ-ray connection of BL Lac objects

2010 ◽  
Author(s):  
S. Kaufmann ◽  
S. Wagner ◽  
I. Jung ◽  
O. Tibolla ◽  
A. Comastri ◽  
...  
Keyword(s):  
Bl Lac Objects ◽  
Bl Lac ◽  
Γ Ray

scholarly journals A Comparison of the X-ray Spectra of Quasars and BL Lac Objects

1989 ◽  
Vol 134 ◽  
pp. 197-198
Author(s):  
D. M. Worrall ◽  
B. J. Wilkes
Keyword(s):  
Power Law ◽  
Radio Spectrum ◽  
Spectral Indices ◽  
Mean Power ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Infrared Frequencies

Quasars with similar core-compact radio properties can be classified by their differences at optical and infrared frequencies. Their X-ray properties might be expected to be similar if the synchrotron self-Compton mechanism relates their radio and X-ray emission. We have compared the 0.2–3.5 keV mean power-law energy spectral indices, , for 4 quasar classes: 12 Highly Polarized QSOs (HPQs), 19 Flat Radio Spectrum, core-compact, low-polarization, QSOs (FRS QSOs), 24 radio-selected BL Lac objects, and 7 X-ray-selected BL Lac objects.

scholarly journals The Environment of OJ 287: Nearby Galaxies and a Long Optical Jet?

1996 ◽  
Vol 175 ◽  
pp. 47-48
Author(s):  
A. Sillanpää ◽  
L. Takalo ◽  
K. Nilsson ◽  
T. Pursimo ◽  
P. Teerikorpi ◽  
...  
Keyword(s):  
Large Scale ◽  
Radio Galaxies ◽  
Trigger Mechanism ◽  
Galaxy Clustering ◽  
Bl Lac Objects ◽  
Close Interaction ◽  
Relativistic Jet ◽  
Bl Lac ◽  
Nearby Galaxies ◽  
Bl Lacs

A widely accepted model for BL Lac objects is that they are radio galaxies with a relativistic jet pointing almost directly towards us. But we need a clear trigger mechanism for these jets. One possibility is the close interaction between the BL Lac host and the closeby galaxies (e.g. Heckman et al. 1986). This interaction has been seen many times in the case of quasars (Hutchings et al. 1989) but not so much is known about the close surroundings of the BL Lac objects although there has been some pioneer work like Stickel et al. (1993). The problem has usually been that the images are not deep enough and that the seeing has not been so good. To clarify the situation we have started an observing program to get very deep images in the sub-arcsecond seeing conditions from the whole 1 Jy sample (Stickel et al. 1991) of BL Lac objects. The aims of this study are: 1. to search for very close companions to the BL Lacs, 2. to study the large scale galaxy clustering around the BL Lacs and 3. to study the BL Lac hosts themselves.

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