FAST continuum mapping of the SNR VRO 42.05.01

2021 ◽  
Author(s):  
Li Xiao ◽  
Ming Zhu ◽  
Xiaohui Sun ◽  
Peng Jiang ◽  
Chun Sun
Keyword(s):  
Spectral Index ◽  
High Frequency ◽  
Supernova Remnants ◽  
Turbulent Medium ◽  
Relativistic Electrons ◽  
Index Distribution ◽  
Shock Density ◽  
Post Shock ◽  
5 Ghz ◽  
Shell Region

Abstract The relativistic electrons rotate in the enhanced magnetic field of the supernova remnants and emit the synchrotron radio emission.We aim to use the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to obtain a sensitive continuum map of the SNR VRO 42.05.01 (G166.0+4.3) at 1240 MHz. The 500 MHz bandwidth is divided into low and high-frequency bands centered at 1085 and 1383 MHz to investigate the spectral index variations within the remnant, together with the Effelsberg 2695 MHz data. We obtained an integrated flux density of 6.2±0.4 Jy at 1240 MHz for VRO 42.05.01, consistent with previous results. The spectral index found from TT-plot between 1240 and 2695 MHz agrees with previous values from 408 MHz up to 5 GHz. The three-band spectral index distribution shows a clear flatter value of α ∼ −0.33 in the shell region and steeper index of α = −0.36 − −0.54 in the wing region. The flatter spectral index in the shell region could be attributed to a second-order Fermi process in the turbulent medium in the vicinity of the shock and/or a higher compression ratio of shock and a high post-shock density than that in elsewhere.

scholarly journals The Spectral Index Distribution of Cygnus A

1982 ◽  
Vol 97 ◽  
pp. 29-31
Author(s):  
P. F. Scott
Keyword(s):  
Magnetic Field ◽  
Spectral Index ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Cygnus A ◽  
Index Distribution ◽  
High Dynamic ◽  
5 Ghz

High dynamic range maps of Cygnus A at 2.7 and 5 GHz have been used to investigate the variation of spectral index over the extended parts of the source. Although both components show a steepening of spectral index away from the hotspots there is a marked asymmetry between the two components. This is interpreted as being due to a higher value of magnetic field in the Sf component.

scholarly journals Thermal radio absorption as a tracer of the interaction of SNRs with their environments

2021 ◽  
Vol 653 ◽  
pp. A62
Author(s):  
G. Castelletti ◽  
L. Supan ◽  
W. M. Peters ◽  
N. E. Kassim
Keyword(s):  
Spectral Index ◽  
Supernova Remnants ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Power Laws ◽  
Line Of Sight ◽  
Pulsar Wind Nebulae ◽  
Very Large Array ◽  
Murchison Widefield Array ◽  
Thermal Absorption

We present new images and continuum spectral analysis for 14 resolved Galactic supernova remnants (SNRs) selected from the 74 MHz Very Large Array Low-Frequency Sky Survey Redux (VLSSr). We combine new integrated measurements from the VLSSr with, when available, flux densities extracted from the Galactic and Extragalactic All-Sky Murchison Widefield Array Survey and measurements from the literature to generate improved integrated continuum spectra sampled from ~15 MHz to ~217 GHz. We present the VLSSr images. When possible we combine them with publicly available images at 1.4 GHz, to analyse the resolved morphology and spectral index distribution across each SNR. We interpret the results and look for evidence of thermal absorption caused by ionised gas either proximate to the SNR itself, or along its line of sight. Three of the SNRs, G4.5+6.8 (Kepler), G28.6−0.1, and G120.1+1.4 (Tycho), have integrated spectra which can be adequately fit with simple power laws. The resolved spectral index map for Tycho confirms internal absorption which was previously detected by the Low Frequency Array, but it is insufficient to affect the fit to the integrated spectrum. Two of the SNRs are pulsar wind nebulae, G21.5−0.9 and G130.7+3.1 (3C 58). For those we identify high-frequency spectral breaks at 38 and 12 GHz, respectively. For the integrated spectra of the remaining nine SNRs, a low frequency spectral turnover is necessary to adequately fit the data. In all cases we are able to explain the turnover by extrinsic thermal absorption. For G18.8+0.3 (Kes 67), G21.8−0.6 (Kes 69), G29.7−0.3 (Kes 75), and G41.1−0.3 (3C 397), we attribute the absorption to ionised gas along the line of sight, possibly from extended H II region envelopes. For G23.3−0.3 (W41) the absorption can be attributed to H II regions located in its immediate proximity. Thermal absorption from interactions at the ionised interface between SNR forward shocks and the surrounding medium were previously identified as responsible for the low frequency turnover in SNR G31.9+0.0 (3C 391); our integrated spectrum is consistent with the previous results. We present evidence for the same phenomenon in three additional SNRs G27.4+0.0 (Kes 73), G39.2–0.3 (3C 396), and G43.3–0.2 (W49B), and derive constraints on the physical properties of the interaction. This result indicates that interactions between SNRs and their environs should be readily detectable through thermal absorption by future low frequency observations of SNRs with improved sensitivity and resolution.

Millimeter-wave absorption properties of BaTiO3/Co3O4 composite powders controlled by high-frequency resonances of permittivity and permeability

2018 ◽  
Vol 6 (47) ◽  
pp. 12965-12975 ◽  
Author(s):  
Wei Tian ◽  
Ruoyang Ma ◽  
Jian Gu ◽  
Zongrong Wang ◽  
Ning Ma ◽  
...  
Keyword(s):  
Millimeter Wave ◽  
High Frequency ◽  
Composite Powders ◽  
Absorption Properties ◽  
Wave Absorption ◽  
Wave Resonance ◽  
Permittivity And Permeability ◽  
5 Ghz

Millimeter-wave resonance of permittivity–permeability-contributed double absorption peaks in BaTiO3/Co3O4, exhibiting RL of ∼−40 dB and a bandwidth of 5 GHz around 35 GHz.

scholarly journals 8.4. Properties of synchrotron emission and magnetic fields in the central region of M31

1998 ◽  
Vol 184 ◽  
pp. 351-352 ◽  
Author(s):  
P. Hoernes ◽  
R. Beck ◽  
E.M. Berkhuijsen
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Spectral Index ◽  
Central Region ◽  
Relativistic Electrons ◽  
Synchrotron Emission ◽  
The Magnetic Field

At the centre of M31 the nonthermal spectral index between λ20 cm and λ6 cm is −0.2. It slowly decreases along the southern arm and the northern filaments visible in Hα, but perpendicular to these features it increases much faster. The magnetic field runs along the arm and the filaments. These phenomena suggest the existence of a mono-energetic source of relativistic electrons in the nucleus.

The interaction of pulsar winds with old supernova remnants

2000 ◽  
Vol 177 ◽  
pp. 513-514
Author(s):  
Eric van der Swaluw ◽  
Abraham Achterberg ◽  
Yves A. Gallant
Keyword(s):  
Cosmic Rays ◽  
Shock Waves ◽  
Radio Emission ◽  
Supernova Remnants ◽  
Charged Particles ◽  
Simple Problem ◽  
Relativistic Electrons ◽  
First Case ◽  
Pulsar Wind ◽  
Pulsar Winds

Shock waves in young supernova remnants (SNR) are generally considered to be the places where production and acceleration of charged particles (relativistic electrons and cosmic rays) take place. Older remnants can be re-energised if an active pulsar catches up with the shell of the remnant (Shull, Fesen, & Saken 1989). In that case a pulsar-driven wind can inject energetic particles into the shell, resulting into a rejuvenation of the radio emission of the old remnant due to the presence of additional relativistic electrons.Radio observations of CTB80 (Angerhofer et al. 1981) and G5.4-1.2 (Frail & Kulkarni 1991) give evidence for the importance of the presence of an active pulsar close to the old shell of the remnants. In the first case the pulsar is believed to be inside the SNR. In the second case the pulsar is thought to have penetrated the shell of the SNR, and resides in the interstellar medium (ISM). We intend to investigate the physics which are connected with these kind of systems. One expects new effects resulting from the interaction of the three different shocks; the SNR shock, the bowshock bounding the pulsar wind nebula (PWN) and the (pulsar) wind termination shock. The dynamics of the system is described by a hydrodynamics code. We use the results from the hydrodynamics code to investigate the process of acceleration and transport of particles which are advected by the flow and diffuse with respect to the flow. We have applied the latter to a simple problem, the case of a spherically expanding SNR.

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