scholarly journals Parsec-scale morphology and spectral-index distribution in faint high-frequency peakers

2012 ◽  
Vol 424 (1) ◽  
pp. 532-544 ◽  
Author(s):  
M. Orienti ◽  
D. Dallacasa
Keyword(s):  
Spectral Index ◽  
High Frequency ◽  
Scale Morphology ◽  
Index Distribution

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 Survey of Milliarcsec Structure in Eight Seyfert Galaxies: Results on NGC 1068 and NGC 4151

1998 ◽  
Vol 164 ◽  
pp. 301-302 ◽  
Author(s):  
A. L. Roy ◽  
J. S. Ulvestad ◽  
E. J. M. Colbert ◽  
A. S. Wilson ◽  
R. P. Norris
Keyword(s):  
Spectral Index ◽  
Low Frequency ◽  
Seyfert Galaxies ◽  
Scale Structure ◽  
Scale Morphology ◽  
Ngc 4151 ◽  
Ngc 1068

AbstractWe are surveying eight nearby Seyfert galaxies (four Sy1s and four Sy2s) that have compact radio cores, using the VLBA. We are interested in parsec-scale morphology and low-frequency absorption effects, and so are observing four frequencies (1.6, 4.8, 8.4 and 15 GHz) to get spectral-index diagnostics. In this paper, we present results on two galaxies, NGC 1068 and NGC 4151. NGC 4151 shows a curved radio jet on the sub-parsec scale, with the smallest scale structure misaligned by 55° from the jet on scales of parsecs to hundreds of parsecs. NGC 1068 contains several components in the inner tens of parsecs, with those components showing a variety of absorption and resolution effects.

scholarly journals A possible mechanism for flattening of pulsar spectra at high frequencies

2000 ◽  
Vol 177 ◽  
pp. 395-396
Author(s):  
I.F. Malov
Keyword(s):  
Spectral Index ◽  
High Frequency ◽  
Linear Part ◽  
Low Frequency ◽  
Usual Model ◽  
High Frequencies ◽  
Unusual Behaviour ◽  
Curvature Radiation

Pulsar spectra have three characteristic parts: a low frequency turnover (the region of the maximum), a linear part with a constant spectral index, and a high frequency cut-off (after it the spectrum becomes considerably steeper) (Malofeev et al. 1994). These three parts can be described in the frame of the usual model of curvature radiation (Malov 1979; Ochelkov & Usov 1984; Kuz’min & Solov’ev 1986; Malov & Malofeev 1991). Kramer et al. (1997) have found a flattening in the spectra of 4 pulsars at frequencies above 30 GHz. It cannot be understood in such model. We propose the possible explanation for the unusual behaviour of these spectra.

scholarly journals Statistical Properties of Compact Sources

1984 ◽  
Vol 110 ◽  
pp. 71-72
Author(s):  
J. Machalski
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
High Frequency ◽  
Density Ratio ◽  
Radio Galaxies ◽  
Statistical Properties ◽  
Identification Rate ◽  
Definition Of ◽  
Image Position ◽  
Compact Sources

The analysis is based on VLA 1465-MHz observations of GB and GB2 sources (Machalski et al. 1982; Machalski and Condon 1983a, 1983b). From those flux-density limited samples compact sources were selected. The following definition of source “compactness” has been used Subjects of analysis were: (a) fraction of compact sources among radio galaxies, quasars, and “empty field” sources, (b) identification rate vs. high-frequency spectral index for compact sources, (c) spectral-index distributions for compact identified and/or EF sources, (d) flux-density ratio for double compact sources, and (e) correlation between radio and optical luminosities for compact sources.

Investigation of cubic non-linearity-driven electrostatic structures in the presence of double spectral index distribution function

2019 ◽  
Vol 60 (1) ◽  
pp. e201900065 ◽  
Author(s):  
M.N.S. Qureshi ◽  
K.H. Shah ◽  
Jiankui Shi ◽  
W. Masood ◽  
H.A. Shah
Keyword(s):  
Distribution Function ◽  
Spectral Index ◽  
Index Distribution

scholarly journals Flickering around the outburst cycle in Kepler dwarf novae

2021 ◽  
Author(s):  
Albert Bruch
Keyword(s):  
Spectral Index ◽  
High Frequency ◽  
Power Spectra ◽  
Light Curves ◽  
Dwarf Novae ◽  
Dwarf Nova ◽  
New Feature ◽  
Nova Outbursts ◽  
High Cadence

Abstract Taking advantage of the unparallel quantity and quality of high cadence Kepler light curves of several dwarf novae, the strength of the flickering and the high frequency spectral index of their power spectra are investigated as a function of magnitude around the outburst cycle of these systems. Previous work suggesting that the flickering strength (on a magnitude scale) is practically constant above a given brightness threshold and only rises at fainter magnitudes is confirmed for most of the investigated systems. As a new feature, a hysteresis in the flickering strength is seen in the sense that at the same magnitude level flickering is stronger during decline from outburst than during the rise. A similar hysteresis is also seen in the spectral index. In both cases, it can qualitatively be explained under plausible assumptions within the DIM model for dwarf nova outbursts.

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