Proceedings of the Conference on Seyfert Galaxies and Related Objects: 21. Radio-Frequency Structure and Time Variations in the Seyfert Galaxies 3C84 and 3CI20

1968 ◽  
Vol 73 ◽  
pp. 874 ◽  
Author(s):  
K. I. Kellerman ◽  
I. Pauliny-Toth
Keyword(s):  
Radio Frequency ◽  
Seyfert Galaxies ◽  
Frequency Structure ◽  
Time Variations

scholarly journals Quantifying excess power from radio frequency interference in Epoch of Reionization measurements

2020 ◽  
Vol 498 (1) ◽  
pp. 265-275
Author(s):  
Michael J Wilensky ◽  
Nichole Barry ◽  
Miguel F Morales ◽  
Bryna J Hazelton ◽  
Ruby Byrne
Keyword(s):  
Power Spectrum ◽  
Radio Frequency ◽  
Flux Density ◽  
Higher Order ◽  
Mitigation Strategies ◽  
Error Tolerance ◽  
Radio Frequency Interference ◽  
Frequency Structure ◽  
Excess Power ◽  
Source Emission

ABSTRACT We quantify the effect of radio frequency interference (RFI) on measurements of the 21-cm power spectrum during the Epoch of Reionization (EoR). Specifically, we investigate how the frequency structure of RFI source emission generates contamination in higher order wave modes, which is much more problematic than smooth-spectrum foreground sources. Using a relatively optimistic EoR model, we find that even a single relatively dim RFI source can overwhelm the EoR power spectrum signal of $\sim 10\, {\rm mK}^2$ for modes $0.1 \ \lt k \lt 2 \, h\, {\rm Mpc}^{-1}$. If the total apparent RFI flux density in the final power spectrum integration is kept below 1 mJy, an EoR signal resembling this optimistic model should be detectable for modes $k \lt 0.9\, h\, {\rm Mpc}^{-1}$, given no other systematic contaminants and an error tolerance as high as 10 per cent. More pessimistic models will be more restrictive. These results emphasize the need for highly effective RFI mitigation strategies for telescopes used to search for the EoR.

scholarly journals High-Energy Gamma-Ray Observations of Active Galaxies

1994 ◽  
Vol 142 ◽  
pp. 917-922
Author(s):  
Carl E. Fichtel
Keyword(s):  
Gamma Ray ◽  
Seyfert Galaxies ◽  
High Energy ◽  
Active Galaxies ◽  
Bl Lacertae ◽  
High Energy Gamma ◽  
Large Numbers ◽  
Wide Range ◽  
Energy Gamma ◽  
Time Variations

AbstractDuring the period from 1992 May to early 1992 November, the Energetic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory obtained high-energy gamma-ray data for most of the sky. A total of 18 active galaxies have been seen with high certainty, and it is expected that more will be found in the data when a more thorough analysis is complete. All of those that have been seen are radio-loud quasars or BL Lacertae objects; most have already been identified as blazars. No Seyfert galaxies have been found thus far. If the spectra are represented as a power law in energy, spectral slopes ranging from approximately −1.7 to −2.4 are found. A wide range of z-values exists in the observed sample, eight having values in excess of 1.0. Time variations have been seen, with the timescale for a significant change being as short as days in at least one case. These results imply the existence of very large numbers of relativistic particles, probably close to the central object. Although a large extrapolation is required, their existence also suggests that these active galactic nuclei may be the source of the extragalactic cosmic rays.Subject headings: acceleration of particles — galaxies: active — gamma rays: observations — quasars: general

Saturn's E, G and F rings: modulated by the plasma sheet

1984 ◽  
Vol 75 ◽  
pp. 597
Author(s):  
E. Grün ◽  
G.E. Morfill ◽  
T.V. Johnson ◽  
G.H. Schwehm
Keyword(s):  
Solar Wind ◽  
Direct Contact ◽  
Transport Processes ◽  
Time Variable ◽  
Dust Particles ◽  
Spatial Diffusion ◽  
Drag Forces ◽  
Orbit Perturbation ◽  
Time Variations ◽  
F Ring

ABSTRACTSaturn's broad E ring, the narrow G ring and the structured and apparently time variable F ring(s), contain many micron and sub-micron sized particles, which make up the “visible” component. These rings (or ring systems) are in direct contact with magnetospheric plasma. Fluctuations in the plasma density and/or mean energy, due to magnetospheric and solar wind processes, may induce stochastic charge variations on the dust particles, which in turn lead to an orbit perturbation and spatial diffusion. It is suggested that the extent of the E ring and the braided, kinky structure of certain portions of the F rings as well as possible time variations are a result of plasma induced electromagnetic perturbations and drag forces. The G ring, in this scenario, requires some form of shepherding and should be akin to the F ring in structure. Sputtering of micron-sized dust particles in the E ring by magnetospheric ions yields lifetimes of 102to 104years. This effect as well as the plasma induced transport processes require an active source for the E ring, probably Enceladus.

46: Intermediate Follow-Up Comparison between Partial Nephrectomy and Radio Frequency Ablation in T1A Renal Tumors

2006 ◽  
Vol 175 (4S) ◽  
pp. 16-16 ◽  
Author(s):  
Joshua M. Stern ◽  
Robert S. Svatek ◽  
Sangtae Park ◽  
J. Kyle Anderson ◽  
Yair Lotan ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Partial Nephrectomy ◽  
Radio Frequency Ablation ◽  
Renal Tumors

1913: The Radiographic Evolution of Radio Frequency Ablated Renal Lesions

2004 ◽  
Vol 171 (4S) ◽  
pp. 505-505
Author(s):  
Edward D. Matsumoto ◽  
Lori Watumall ◽  
D. Brooke Johnson ◽  
Kenneth Ogan ◽  
Grant D. Taylor ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Renal Lesions
Sign in / Sign up

Export Citation Format

Share Document