122 research outputs found
Plerionic Supernova Remnants
Plerions represent ideal laboratories for the search for neutron stars, the
study of their relativistic winds, and their interaction with their surrounding
supernova ejecta and/or the interstellar medium. As well, they are widely
believed to represent efficient engines for particle acceleration up to the
knee of the cosmic ray spectrum (at about 1E15 eV). Multi-wavelength
observations from the radio to the highest TeV energies, combined with
modelling, have opened a new window to study these objects, and particularly
shed light on their intrinsic properties, diversity, and evolution.
High-resolution X-ray observations are further revealing the structure and
sites for shock acceleration. The missing shells in the majority of these
objects remain puzzling, and the presence of plerions around highly magnetized
neutron stars is still questionable. I review the current status and statistics
of observations of plerionic supernova remnants (SNRs), highlighting combined
radio and X-ray observations of a growing class of atypical, non Crab-like,
plerionic SNRs in our Galaxy. I will also briefly describe the latest
developments to our high-energy SNRs catalogue recently released to the
community, and finally highlight the key questions to be addressed in this
field with future high-energy missions, including Astro-H in the very near
future.Comment: AIP Conference Proceedings of the 5th International Symposium on
High-Energy Gamma-Ray Astronomy, Heidelberg, July 9-13 (2012). Eds: F.
Aharonian, W. Hofmann, F. Rieger. Solicited review, 8 pages, 4 colour
figures. The figures resolution has been reduced for astro-ph. Original
article can be found at:
http://www.physics.umanitoba.ca/~samar/arxiv/safiharb-plerions-gamma2012.pd
SS 433: Radio/X-ray anti-correlation and fast-time variability
We briefly review the Galactic microquasar SS 433/W50 and present a new RXTE
spectral and timing study. We show that the X-ray flux decreases during radio
flares, a behavior seen in other microquasars. We also find short time-scale
variability unveiling emission regions from within the binary system.Comment: 4 pages, 3 figures, mq.sty included. A higher resolution version can
be found at http://aurora.physics.umanitoba.ca/~samar/4MQ/ss433/. Proceedings
of the 4th Microquasar Workshop, eds. Ph. Durouchoux, Y. Fuchs and J.
Rodriguez, published by the Center for Space Physics: Kolkata (in press
3D Simulations of the Thermal X-ray Emission from Young Supernova Remnants Including Efficient Particle Acceleration
Supernova remnants (SNRs) are believed to be the major contributors to
Galactic cosmic rays. The detection of non-thermal emission from SNRs
demonstrates the presence of energetic particles, but direct signatures of
protons and other ions remain elusive. If these particles receive a sizeable
fraction of the explosion energy, the morphological and spectral evolution of
the SNR must be modified. To assess this, we run 3D hydrodynamic simulations of
a remnant coupled with a non-linear acceleration model. We obtain the
time-dependent evolution of the shocked structure, impacted by the
Rayleigh-Taylor hydrodynamic instabilities at the contact discontinuity and by
the back-reaction of particles at the forward shock. We then compute the
progressive temperature equilibration and non-equilibrium ionization state of
the plasma, and its thermal emission in each cell. This allows us to produce
the first realistic synthetic maps of the projected X-ray emission from the
SNR. Plasma conditions (temperature, ionization age) can vary widely over the
projected surface of the SNR, especially between the ejecta and the ambient
medium owing to their different composition. This demonstrates the need for
spatially-resolved spectroscopy. We find that the integrated emission is
reduced with particle back-reaction, with the effect being more significant for
the highest photon energies. Therefore different energy bands, corresponding to
different emitting elements, probe different levels of the impact of particle
acceleration. Our work provides a framework for the interpretation of SNR
observations with current X-ray missions (Chandra, XMM-Newton, Suzaku) and with
upcoming X-ray missions (such as Astro-H).Comment: Accepted for publication in ApJ. Figures quality has been reduced for
the arXi
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