1,513 research outputs found
GeV Analysis of Mixed Morphology Supernova Remnants Interacting with Molecular Clouds
The first remnants detected by the Fermi Gamma-ray Space Telescope were of
the type of mixed-morphology supernova remnants interacting with molecular
clouds. In this paper we are presenting preliminary results of the gamma-ray
analysis of 4 selected mixed morphology remnants, G359.1-0.5, G337.8-0.1,
G001.0-0.1, and G346.6-0.2, as well as G349.7+0.2, in the 0.2 - 300 GeV energy
range from the data collected by Fermi Gamma-ray Space Telescope for 3 years.
G359.1-0.5, G337.8-0.1, and G349.7+0.2 were all detected with significances
above 5 sigma. The excess distribution of G359.1-0.5 shows extended gamma-ray
emission, which coincides with the TeV gamma-ray source HESS J1745-303.
G337.8-0.1 also shows an extended nature.Comment: High Energy Gamma-Ray Astronomy: 5th International Meeting on High
Energy Gamma-Ray Astronom
GCD matrices, posets, and nonintersecting paths
We show that with any finite partially ordered set one can associate a matrix
whose determinant factors nicely. As corollaries, we obtain a number of results
in the literature about GCD matrices and their relatives. Our main theorem is
proved combinatorially using nonintersecting paths in a directed graph.Comment: 10 pages, see related papers at http://www.math.msu.edu/~saga
What\u27s in a Name: Are Counseling Psychologists Truly Scientist-Practitioners?
The integration of research and practice is essential to the identities of counseling psychologists (Meula et al., 2008). Despite this admonition, many counseling psychologists struggle to synthesize research and clinical work (Norcross, 1981). The present paper will examine special considerations for integrating research advances into psychological practice
The Effects of Shear and Rotation Anisotropy Upon the Process of Gravitational Instability
In this paper, we study the role of shear fields on the evolution of density
perturbations embedded in a Friedmann flat background universe, by studying the
evolution of a homogeneous ellipsoid model. In this context, we show that while
the effect of the shear is that of increasing the growth rate of the density
contrast of a mass element, the angular momentum acquired by the ellipsoid has
the right magnitude to counterbalance the shear. Finally, our result show that
initial asphericities and tidal interaction induce a slowing down of the
collapse after the system has broken away from the general expansion, in
perfect agreement with the previrialization conjecture (Peebles & Groth 1976;
Davis & Peebles 1977)
Origin of gamma-ray emission in the shell of Cassiopeia A
Non-thermal X-ray emission from the shell of Cassiopeia A (Cas A) has been an
interesting subject of study, as it provides information about relativistic
electrons and their acceleration mechanisms in the shocks. Chandra X-ray
observatory revealed the detailed spectral and spatial structure of this SNR in
X-rays. The spectral analysis of Chandra X-ray data of Cas A shows unequal flux
levels for different regions of the shell, which can be attributed to different
magnetic fields in those regions. Additionally, the GeV gamma-ray emission
observed by Large Area Telescope on board Fermi Gamma Ray Space Telescope
showed that the hadronic processes are dominating in Cas A, a clear signature
of acceleration of protons. In this paper we aim to explain the GeV-TeV
gamma-ray data in the context of both leptonic and hadronic scenario. We
modeled the multi-wavelength spectrum of Cas A. We use synchrotron emission
process to explain the observed non-thermal X-ray fluxes from different regions
of the shell. These result in estimation of the model parameters, which are
then used to explain TeV gamma-ray emission spectrum. We also use hadronic
scenario to explain both GeV and TeV fluxes simultaneously. We show that a
leptonic model alone cannot explain the GeV-TeV data. Therefore, we need to
invoke a hadronic model to explain the observed GeV-TeV fluxes. We found that
although pure hadronic model is able to explain the GeV-TeV data, a
lepto-hadronic model provides the best fit to the data.Comment: Accepted in A&
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