Search results for "blazar"

The blazar-like radio structure of the TeV source IC310

2012

Context. The radio galaxy IC310 in the Perseus cluster has recently been detected in the gamma-ray regime at GeV and TeV energies. The TeV emission shows time variability and an extraordinarily hard spectrum, even harder than the spectrum of the similar nearby gamma-ray emitting radio galaxy M87. Aims. High-resolution studies of the radio morphology help to constrain the geometry of the jet on sub-pc scales and to find out where the high-energy emission might come from. Methods. We analyzed May 2011 VLBA data of IC310 at a wavelength of 3.6 cm, revealing the parsec-scale radio structure of this source. We compared our findings with more information available from contemporary single-dish fl…

Multi-frequency properties of synthetic blazar radio light curves within the shock-in-jet scenario

2015

Blazars are among the most powerful extragalactic objects, as a sub-class of active galactic nuclei. They launch relativistic jets and their emitted radiation shows strong variability across the entire electro-magnetic spectrum. The mechanisms producing the variability are still controversial and different models have been proposed to explain the observed variations in multi-frequency blazar light curves.We investigate the capabilities of the classical shock-in-jet model to explain and reconstruct the observed evolution of flares in the turnover frequency turnover flux density plane and their frequency-dependent light curve parameters. With a detailed parameter space study we provide the fr…

Evidence for shock-shock interaction in the jet of CTA 102

2010

We have found evidence for interaction between a standing and a traveling shock in the jet of the blazar CTA 102. Our result is based in the study of the spectral evolution of the turnover frequency-turnover flux density plane. The radio/mm light curves were taken during a major radio outburst in April 2006.

The unusual multiwavelength properties of the gamma-ray source PMN J1603-4904

2013

We investigate the nature and classification of PMNJ1603-4904, a bright radio source close to the Galactic plane, which is associated with one of the brightest hard-spectrum gamma-ray sources detected by Fermi/LAT. It has previously been classified as a low-peaked BL Lac object based on its broadband emission and the absence of optical emission lines. Optical measurements, however, suffer strongly from extinction and the absence of pronounced short-time gamma-ray variability over years of monitoring is unusual for a blazar. We are combining new and archival multiwavelength data in order to reconsider the classification and nature of this unusual gamma-ray source. For the first time, we stud…

Long-term monitoring of mrk 501 for its very high energy γ emission and a flare in 2011 october

2012

"As one of the brightest active blazars in both X-ray and very high energy γ -ray bands, Mrk 501, is very useful for" "physics associated with jets from active galactic nuclei. The ARGO-YBJ experiment has monitored Mrk 501 for γ - rays above 0.3 TeV since 2007 November. The largest flare since 2005 was observed from 2011 October and lasted until about 2012 April. In this paper, a detailed analysis of this event is reported. During the brightest γ -ray flaring episodes from 2011 October 17 to November 22, an excess of the event rate over 6σ is detected by ARGO-YBJ in the direction of Mrk 501, corresponding to an increase of the γ -ray flux above 1 TeV by a factor of 6.6 ± 2.2 from its steady…

γ-RAY AND PARSEC-SCALE JET PROPERTIES OF A COMPLETE SAMPLE OF BLAZARS FROM THE MOJAVE PROGRAM

2011

著者人数: 145名

ERRATUM: “MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. VII. BLAZAR JET ACCELERATION” (2009, ApJ, 706, 1253)

2014

A Search for Ultra-high-energy Neutrinos from TXS 0506+056 Using the Pierre Auger Observatory

2020

Results of a search for ultra-high-energy neutrinos with the Pierre Auger Observatory from the direction of the blazar TXS 0506+056 are presented. They were obtained as part of the follow-up that stemmed from the detection of high-energy neutrinos and gamma rays with IceCube, Fermi-LAT, MAGIC, and other detectors of electromagnetic radiation in several bands. The Pierre Auger Observatory is sensitive to neutrinos in the energy range from 100 PeV to 100 EeV and in the zenith-angle range from θ = 60° to θ = 95°, where the zenith angle is measured from the vertical direction. No neutrinos from the direction of TXS 0506+056 have been found. The results were analyzed in three periods: One of 6 m…

Faint γ-ray sources at low redshift: the radio galaxy IC 1531

2018

We present amultiwavelength study of IC 1531 (z=0.02564), an extragalactic radio source associated with the γ -ray object 3FGL J0009.9-3206 and classified as a blazar of uncertain type in the Third Fermi-Large Area Telescope AGN catalog (3LAC). A core-jet structure, visible in radio and X-rays, is enclosed within a ~220 kpc wide radio structure. The morphology and spectral characteristics of the kiloparsec jet in radio and X-rays are typical of Fanaroff-Riley type I galaxies. The analysis of the radio data and optical spectrum and different diagnostic methods based on the optical, infrared, and γ -ray luminosities also support a classification as a low-power RG seen at moderate angles (θ = …

MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. VII. BLAZAR JET ACCELERATION

2009

We discuss acceleration measurements for a large sample of extragalactic radio jets from the Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments (MOJAVE) program, which studies the parsec-scale jet structure and kinematics of a complete, flux-density-limited sample of active galactic nuclei (AGNs). Accelerations are measured from the apparent motion of individual jet features or 'components' which may represent patterns in the jet flow. We find that significant accelerations are common both parallel and perpendicular to the observed component velocities. Parallel accelerations, representing changes in apparent speed, are generally larger than perpendicular acceleration that r…