scholarly journals PARSEC-SCALE JET BEHAVIOR OF THE QUASAR 3C273 DURING A HIGH GAMMA-RAY STATE IN 2009–2010

2012 ◽  
Vol 08 ◽  
pp. 356-359 ◽  
Author(s):  
S. JORSTAD ◽  
A. MARSCHER ◽  
P. SMITH ◽  
V. LARIONOV ◽  
I. AGUDO ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Jet Flow ◽  
Strong Increase ◽  
Optical Variability ◽  
Optical Polarization ◽  
High Gamma ◽  
Jet Behavior ◽  
Intensity Images ◽  
Γ Ray

We analyze total and polarized intensity images of the quasar 3C273 obtained at 43 GHz monthly during 2008-2010 with the VLBA. We find a strong increase of activity in the parsec-scale jet during a high γ-ray state lasting from 2009 June to 2010 May featuring an increase of the total and polarized flux in the mm-wave core and the appearance of superluminal knots in the jets. Although the optical variability is low, owing to strong contamination by the big blue bump, we observe an increase in optical polarization by a factor of 3 during a gamma-ray flare in 2010 April. We discuss the locations in the jet where high gamma-ray fluxes occur. These include stationary features in the jet flow that we identify with standing shocks.

scholarly journals Gamma-Ray Imaging of the Galactic Center Region

1989 ◽  
Vol 136 ◽  
pp. 581-585
Author(s):  
W. R. Cook ◽  
D. M. Palmer ◽  
T. A. Prince ◽  
S. M. Schindler ◽  
C. H. Starr ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Galactic Center ◽  
Coded Aperture ◽  
Center Region ◽  
Gamma Ray Imaging ◽  
The Galaxy ◽  
Γ Ray ◽  
Luminous Objects

The Caltech imaging γ-ray telescope was launched by balloon from Alice Springs, NT, Australia and performed observations of the galactic center during the period 12.62 to 13.00 April 1988 UT. The first coded-aperture images of the galactic center region at energies above 30 keV show a single strong γ-ray source which is located 0.7±0.1° from the galactic nucleus and is tentatively identified as 1E1740.7-2942. If the source is at the distance of the galactic center, it is one of the most luminous objects in the galaxy at energies from 35 to 200 keV.

CCD Photometry and Optical Variability of Gamma-Ray-loud BL Lacertae Object OJ 287 in a Low, Fainter State

2007 ◽  
Vol 133 (5) ◽  
pp. 1995-2000 ◽  
Author(s):  
X. Zhang ◽  
G. Zhao ◽  
Y. G. Zheng ◽  
L. Ma ◽  
Z. H. Xie ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Optical Variability ◽  
Ccd Photometry ◽  
Bl Lacertae

scholarly journals Molecular Clouds Observed by the EGRET Gamma-Ray Telescope

1997 ◽  
Vol 170 ◽  
pp. 22-24 ◽  
Author(s):  
Seth. W. Digel ◽  
Stanley D. Hunter ◽  
Reshmi Mukherjee ◽  
Eugéne J. de Geus ◽  
Isabelle A. Grenier ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Molecular Clouds ◽  
Gamma Ray ◽  
Angular Resolution ◽  
Cosmic Ray ◽  
High Energy ◽  
Background Rejection ◽  
Γ Rays ◽  
Γ Ray ◽  
Production Mechanisms

EGRET, the high-energy γ-ray telescope on the Compton Gamma-Ray Observatory, has the sensitivity, angular resolution, and background rejection necessary to study diffuse γ-ray emission from the interstellar medium (ISM). High-energy γ rays produced in cosmic-ray (CR) interactions in the ISM can be used to determine the CR density and calibrate the CO line as a tracer of molecular mass. Dominant production mechanisms for γ rays of energies ∼30 MeV–30 GeV are the decay of pions produced in collisions of CR protons with ambient matter and Bremsstrahlung scattering of CR electrons.

scholarly journals Optical Variability Monitoring for Gamma ray Blazars: preliminary results

2009 ◽  
Author(s):  
Jorge Ariel Combi ◽  
Ileana Andruchow ◽  
Sergio Aldo Cellone ◽  
Gustavo E. Romero ◽  
Josep Martí ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Optical Variability ◽  
Preliminary Results

scholarly journals Attempted study of the 237Np(n,2n)236Np reaction cross section at 9.5 MeV

2019 ◽  
Vol 18 ◽  
pp. 101
Author(s):  
M. Diakaki ◽  
R. Vlastou ◽  
M. Kokkoris ◽  
C. T. Papadopoulos ◽  
A. Tsinganis ◽  
...  
Keyword(s):  
Cross Section ◽  
Gamma Ray ◽  
Gamma Spectroscopy ◽  
Reaction Cross ◽  
Activation Technique ◽  
Incident Neutron ◽  
Incident Neutron Energy ◽  
Tandem Accelerator ◽  
Section Measurement ◽  
High Gamma

The cross section measurement of the 237Np(n,2n)236Np reaction has been attempted at an incident neutron energy of 9.5 MeV by means of the activation technique. The neutron beam was produced via the 2H(d,n)3Ηe reaction at the VdG Tandem accelerator of NCSR “Demokritos”. It is the second time that this measurement has been tried with a gamma spectroscopy method and the difficulties faced due to the high gamma ray background produced by the sample itself and the fission fragments produced by the irradiation, in combination with the very low intensity of the gamma ray of interest are being reported.

scholarly journals Fermi-LAT and WMAP observations of the supernova remnant Puppis A

2013 ◽  
Vol 9 (S296) ◽  
pp. 295-299
Author(s):  
Marie-Hélène Grondin ◽  
John W. Hewitt ◽  
Marianne Lemoine-Goumard ◽  
Thierry Reposeur ◽  
Keyword(s):  
Supernova Remnants ◽  
Supernova Remnant ◽  
Gamma Ray ◽  
High Energy ◽  
Radio Spectrum ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Large Area ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Γ Ray

AbstractThe supernova remnant (SNR) Puppis A (aka G260.4-3.4) is a middle-aged supernova remnant, which displays increasing X-ray surface brightness from West to East corresponding to an increasing density of the ambient interstellar medium at the Eastern and Northern shell. The dense IR photon field and the high ambient density around the remnant make it an ideal case to study in γ-rays. Gamma-ray studies based on three years of observations with the Large Area Telescope (LAT) aboard Fermi have revealed the high energy gamma-ray emission from SNR Puppis A. The γ-ray emission from the remnant is spatially extended, and nicely matches the radio and X-ray morphologies. Its γ-ray spectrum is well described by a simple power law with an index of ~2.1, and it is among the faintest supernova remnants yet detected at GeV energies. To constrain the relativistic electron population, seven years of Wilkinson Microwave Anisotropy Probe (WMAP) data were also analyzed, and enabled to extend the radio spectrum up to 93 GHz. The results obtained in the radio and γ-ray domains are described in detail, as well as the possible origins of the high energy γ-ray emission (Bremsstrahlung, Inverse Compton scattering by electrons or decay of neutral pions produced by proton interactions).

Effect of γ-ray irradiation on performance of LiNbO(3)-based piezoelectric vibration sensors

2021 ◽  
Author(s):  
Huifen Wei ◽  
Wenping Geng ◽  
Kaixi Bi ◽  
Tao Li ◽  
Xiangmeng Li ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Extreme Environments ◽  
Theoretical Work ◽  
High Dose ◽  
Mems Devices ◽  
Micro Electro Mechanical Systems ◽  
Vibration Sensors ◽  
Irradiation Dosage ◽  
Gamma Ray Irradiation ◽  
Γ Ray

Abstract LiNbO3 (LN)-based micro-electro-mechanical systems (MEMS) vibration sensors exhibit giant prospection in extreme environments, where exist a great amount of irradiation. However, to the best of our knowledge, it is still unknown whether the irradiation affects the performance of LN-based piezoelectric MEMS sensors. Based on this consideration, it is necessary to model the irradiation environment to investigate the effect of high dosage irradiation on LN-based vibration sensors. Firstly, the theoretical work is done to study the Compton Effect on the Gamma-ray irradiation with Co-60 source. After irradiation, X-ray diffraction (XRD) characterization was performed to verify the effect of irradiation on the crystalline of LN thin film. Meanwhile, the performances of output voltages on the five MEMS devices under various dosage of irradiation are compared. As a result, a neglected shift of 0.02 degrees was observed from the XRD image only under maximum irradiation dosage of 100 Mrad(Si). Moreover, the output voltages of cantilever-beam vibration sensors decrease by 3.1%. Therefore, it is verified that the γ-ray irradiation has very little influence on the LN-based MEMS vibration sensors, which have great attraction on the materials and sensors under high-dose irradiation.

scholarly journals X-ray and Gamma-ray Radiation from the Switched-off Radiopulsars

1983 ◽  
Vol 101 ◽  
pp. 505-507
Author(s):  
A. I. Tsygan
Keyword(s):  
Neutron Stars ◽  
Magnetic Dipole ◽  
Gamma Ray ◽  
Neutral Hydrogen ◽  
Dipole Radiation ◽  
X Ray ◽  
Electron Positron ◽  
Hard Radiation ◽  
Γ Ray ◽  
Generate Electron

It is shown that pulsars that have ceased to generate electron-positron pairs (switched-off radiopulsars) may be the sources of X-ray and γ-ray radiation. The magnetic dipole radiation from these rotating neutron stars is transformed near the “light radius” into hard radiation by the plasma that is created due to ionization of interstellar neutral hydrogen.

Sign in / Sign up

Export Citation Format

Share Document