scholarly journals Simulations of starburst spectral evolution superimposed on old populations: extension to dwarf ellipticals

1995 ◽  
Vol 273 (4) ◽  
pp. 945-957 ◽  
Author(s):  
A. A. Schmidt ◽  
D. Alloin ◽  
E. Bica
Keyword(s):  
Spectral Evolution

scholarly journals Limits on quantum gravity effects from Swift short gamma-ray bursts

2017 ◽  
Vol 607 ◽  
pp. A121 ◽  
Author(s):  
M. G. Bernardini ◽  
G. Ghirlanda ◽  
S. Campana ◽  
P. D’Avanzo ◽  
J.-L. Atteia ◽  
...  
Keyword(s):  
Quantum Gravity ◽  
Gamma Ray ◽  
Lorentz Invariance ◽  
Spectral Energy Distribution ◽  
Gamma Ray Bursts ◽  
Low Energy ◽  
Energy Separation ◽  
Spectral Energy ◽  
Spectral Evolution ◽  
Short Grbs

The delay in arrival times between high and low energy photons from cosmic sources can be used to test the violation of the Lorentz invariance (LIV), predicted by some quantum gravity theories, and to constrain its characteristic energy scale EQG that is of the order of the Planck energy. Gamma-ray bursts (GRBs) and blazars are ideal for this purpose thanks to their broad spectral energy distribution and cosmological distances: at first order approximation, the constraints on EQG are proportional to the photon energy separation and the distance of the source. However, the LIV tiny contribution to the total time delay can be dominated by intrinsic delays related to the physics of the sources: long GRBs typically show a delay between high and low energy photons related to their spectral evolution (spectral lag). Short GRBs have null intrinsic spectral lags and are therefore an ideal tool to measure any LIV effect. We considered a sample of 15 short GRBs with known redshift observed by Swift and we estimate a limit on EQG ≳ 1.5 × 1016 GeV. Our estimate represents an improvement with respect to the limit obtained with a larger (double) sample of long GRBs and is more robust than the estimates on single events because it accounts for the intrinsic delay in a statistical sense.

scholarly journals Microwave Spectral Evolution of Solar Flares

2007 ◽  
Vol 59 (2) ◽  
pp. 373-379 ◽  
Author(s):  
Zongjun Ning ◽  
Mingde Ding
Keyword(s):  
Solar Flares ◽  
Spectral Evolution

Spectral Evolution of Swift Gamma-ray Burst Tails: an Update

2010 ◽  
Author(s):  
V. Mangano ◽  
B. Sbarufatti ◽  
Nobuyuki Kawai ◽  
Shigehiro Nagataki
Keyword(s):  
Gamma Ray ◽  
Spectral Evolution ◽  
Gamma Ray Burst

scholarly journals Curvature Effect of a Non-Power-Law Spectrum and Spectral Evolution of GRB X-Ray Tails

2008 ◽  
Author(s):  
Bin-Bin Zhang ◽  
Bing Zhang ◽  
En-Wei Liang ◽  
Xiang-Yu Wang ◽  
Yong-Feng Huang ◽  
...  
Keyword(s):  
Power Law ◽  
Curvature Effect ◽  
Spectral Evolution ◽  
X Ray

scholarly journals Spectral evolution of weak bursts from SGR 1806–20 observed with INTEGRAL

2004 ◽  
Vol 417 (3) ◽  
pp. L45-L48 ◽  
Author(s):  
D. Götz ◽  
S. Mereghetti ◽  
I. F. Mirabel ◽  
K. Hurley
Keyword(s):  
Spectral Evolution

scholarly journals Spectral evolution of Fermi/GBM short gamma-ray bursts

2010 ◽  
Vol 410 (1) ◽  
pp. L47-L51 ◽  
Author(s):  
G. Ghirlanda ◽  
G. Ghisellini ◽  
L. Nava ◽  
D. Burlon
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Spectral Evolution

scholarly journals On the structure of the self-sustaining cycle in separating and reattaching flows

2018 ◽  
Vol 857 ◽  
pp. 907-936 ◽  
Author(s):  
A. Cimarelli ◽  
A. Leonforte ◽  
D. Angeli
Keyword(s):  
Shear Layer ◽  
Rectangular Plate ◽  
Large Scale ◽  
Reverse Flow ◽  
Leading Edge ◽  
Streamwise Velocity ◽  
The Self ◽  
Small Scale ◽  
Spectral Evolution ◽  
Mean Velocity

The separating and reattaching flows and the wake of a finite rectangular plate are studied by means of direct numerical simulation data. The large amount of information provided by the numerical approach is exploited here to address the multi-scale features of the flow and to assess the self-sustaining mechanisms that form the basis of the main unsteadinesses of the flows. We first analyse the statistically dominant flow structures by means of three-dimensional spatial correlation functions. The developed flow is found to be statistically dominated by quasi-streamwise vortices and streamwise velocity streaks as a result of flow motions induced by hairpin-like structures. On the other hand, the reverse flow within the separated region is found to be characterized by spanwise vortices. We then study the spectral properties of the flow. Given the strongly inhomogeneous nature of the flow, the spectral analysis has been conducted along two selected streamtraces of the mean velocity field. This approach allows us to study the spectral evolution of the flow along its paths. Two well-separated characteristic scales are identified in the near-wall reverse flow and in the leading-edge shear layer. The first is recognized to represent trains of small-scale structures triggering the leading-edge shear layer, whereas the second is found to be related to a very large-scale phenomenon that embraces the entire flow field. A picture of the self-sustaining mechanisms of the flow is then derived. It is shown that very-large-scale fluctuations of the pressure field alternate between promoting and suppressing the reverse flow within the separation region. Driven by these large-scale dynamics, packages of small-scale motions trigger the leading-edge shear layers, which in turn created them, alternating in the top and bottom sides of the rectangular plate with a relatively long period of inversion, thus closing the self-sustaining cycle.

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