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This book presents a study of the young supernova remnant RX J1713.7-3946 in order to reveal the origin of cosmic rays in our galaxy. The study focuses on the X-ray and gamma radiation from the cosmic ray electrons and protons in the supernova remnant as well as the emission from the surrounding interstellar gas measured by the NANTEN2 4-m radio telescope at Nagoya University. The gamma rays show a good spatial correspondence with the interstellar gas, which for the first time provides strong evidence of the acceleration of cosmic ray protons. Additionally, the author determines that an interaction between the supernova shockwaves and interstellar gas, referred to as “shock-cloud interaction,” promotes the efficient acceleration of cosmic ray electrons in the supernova remnant. The book reveals that the interstellar gas plays an essential role in producing the high-energy radiation and cosmic rays, offering vital new insights into the origin and behavior of galactic cosmic rays.
Written by a leading expert, this monograph presents recent developments on supernova remnants, with the inclusion of results from various satellites and ground-based instruments. The book details the physics and evolution of supernova remnants, as well as provides an up-to-date account of recent multiwavelength results. Supernova remnants provide vital clues about the actual supernova explosions from X-ray spectroscopy of the supernova material, or from the imprints the progenitors had on the ambient medium supernova remnants are interacting with - all of which the author discusses in great detail. The way in which supernova remnants are classified, is reviewed and explained early on. A chapter is devoted to the related topic of pulsar wind nebulae, and neutron stars associated with supernova remnants. The book also includes an extended part on radiative processes, collisionless shock physics and cosmic-ray acceleration, making this book applicable to a wide variety of astronomical sub-disciplines. With its coverage of fundamental physics and careful review of the state of the field, the book serves as both textbook for advanced students and as reference for researchers in the field.
The Galactic cosmic rays have far-reaching effects on the interstellar medium, and they are, in turn, profoundly affected by the particles and fields in space. Supernova remnants and their expanding shock fronts pervade the Galaxy, heating the interstellar medium, and accelerating the cosmic rays. The interplay among the cosmic rays, the interstellar medium in which they propagate, and supernovae has been investigated for decades; yet these studies have generated as many enigmas as they have resolved. These puzzles continue to challenge observers and theorists alike. th This volume is devoted to selected lectures presented in the 7 Course of the International School of Cosmic-Ray Astrophysics in Erice, Italy in July-August, 1990. Alltogether, some 400 participants have attended the biennial sessions of this School since its inception in 1978. As its name implies, the School deals with cosmic-ray phenomena viewed in the broader context of astrophysics. Students and Lecturers are attracted from many astrophysical disciplines. Like earlier courses in this series, the present one was organized under the aegis of the Ettore Majorana Centre as a NATO Advanced Study Institute. Given the diverse scientific backgrounds of the students, it was deemed useful to include lectures at the introductory level. Other lectures and contributed talks were at a more advanced level, featuring new developments. If this collection is useful pedagogically, and if it provides some stimulus and information for the mature research worker, then the editors will feel well rewarded.
Supernova remnants are believed to be the source of cosmic rays with energies up to 10^15 eV that are produced within our Galaxy. The acceleration mechanism associated with the collision-less shocks in supernova remnants - diffusive shock acceleration - predicts a spectral index of the accelerated non-thermal particles of s = 2. However, measurements of non-thermal emission in radio, X-rays and gamma-rays reveal significant deviations of the particles spectral index from the canonical value of s = 2. The youngest Galactic supernova remnant G1.9+0.3 is an interesting target for next-generation gamma-ray observatories. So far, the remnant is only detected in the radio and the X-ray bands, but its young age of ≈100 yrs and inferred shock speed of ≈ 14, 000 km/s could make it an efficient particle accelerator. I performed spherical symmetric 1D simulations with the RATPaC code, in which I simultaneously solved the transport equation for cosmic rays, the transport equation for magnetic turbulence, and the hydro-dynamical equations for ...
Supernova remnants (SNRs) are the only class of sources known in our Galaxy capable of providing the energy necessary to power the bulk of the Galactic cosmic-rays (CRs) below the `knee' (~ 3 PeV). They are observable across the entire frequency spectrum from radio to TeV gamma-rays, and are known to exhibit a rich variety of complex morphologies in multi-wavelength. Non-thermal emissions from SNRs in X-ray and gamma-ray arise from interaction between particles accelerated by the SNR blast wave and the surrounding medium, and are hence one of the most useful probe for the Galactic CR production process. In this thesis, we will try to obtain a fuller understanding of the origin of Galactic CRs through studying non-thermal emissions from SNRs and modelling CR injection from their astrophysical accelerators. In the first part of the thesis, we will develop a robust tool to simulate time and space-resolved broadband emission from young shell-type SNRs using coupled hydrodynamic and diffusive shock acceleration (DSA) calculations. Usually, the DSA process is expected to be highly non-linear for young SNRs due to a number of postulated coupling phenomena, which leads to the inter-correlation of the emission spectra and morphology at different wavelengths. Therefore, to gain the full picture, it is important to combine multi-wavelength observations and the relevant physical processes into a self-consistent and flexible calculation framework. By taking into account particle transport, escape, interaction and various radiative processes, our tool can predict photon emissivity in full three-dimension and multi-wavelength for any given SNR model and surrounding environment, such as in the presence of a nearby molecular cloud. Through illustrations using a few typical models for Type Ia SNR, we will demonstrate its capability of calculating results directly comparable to observations, as well as to pinpoint the gamma-ray emission mechanism, namely the leptonic and hadronic scenarios. In the second part, we will study the gamma-ray emission from a middle-aged SNR IC 443 (G189.1+3.0) using the Fermi Large Area Telescope (LAT). IC 443 has been extensively studied in the past few decades through radio to TeV gamma-ray, but high quality data in the sub-GeV to sub-TeV band, the most crucial window for constraining the origin of the high-energy emission, has still been missing. We will fill in this gap by analyzing LAT data from 200 MeV to 50 GeV using the 1st year of LAT data. Equipped with the high photon statistics available, and the excellent resolution, sensitivity and low background rate of LAT, we are able to probe the gamma-ray emission from IC 443 with minimal confusion with the backgrounds. We discovered spatially extended emission from IC 443 in the 1 - 50 GeV band for the first time, which eliminates the pulsar wind nebula (PWN) as the dominating gamma-ray emitter. We found good spatial correlation of the GeV mission with the TeV source recently detected by VERITAS, as well as a known group of ambient and shocked molecular clouds (MC). The sub-GeV to TeV broadband spectrum can be described by a power-law with a smooth break at a few GeV, the same feature also observed from several other LAT-detected middle-aged SNRs interacting with MCs. We will argue that the gamma-ray emission is most naturally explained by a neutral pion decay dominated origin, and the leptonic scenarios are disfavored. Finally, we will also discuss the major discoveries from LAT observations of other gamma-ray bright Galactic SNRs during the first 2 years of operation of Fermi. In the last part, we will construct a model of Galactic CR injection using constraints from most recent GeV and TeV observation data and CR measurements, which can provide a natural explanation for the enhanced positron flux above 10 GeV recently observed by PAMELA as compared to previous measurements. Without making speculation on `additional' positron contribution from any special nearby objects or resorting to exotic phenomena, we will look at a steady-state picture of our Galaxy in which the ensembles of SNRs and PWNe steadily inject CRs into the interstellar space. Using the GALPROP CR propagation code, the CR spectra and ratios at Earth are calculated and compared with data. Without tweaking the model parameters specifically to fit the positron data other than using observation and astrophysics-based assumptions, we will show that this steady-state model can satisfactorily reproduce the positron enhancement and other CR measurement results. Assisted by recent observations of middle-aged SNRs interacting with MCs by Fermi LAT, we are also able to set an upper-limit on the total number of these systems residing in our Galaxy. Finally, using this consistent model, we will estimate the energy budgets of the major species of Galactic CRs.
Gamma ray astronomy, the branch of high energy astrophysics that studies the sky in energetic ?-ray photons, is destined to play a crucial role in the exploration of nonthermal phenomena in the Universe in their most extreme and violent forms. The great potential of this discipline offers impressive coverage of many OC hot topicsOCO of modern astrophysics and cosmology, such as the origin of galactic and extragalactic cosmic rays, particle acceleration and radiation processes under extreme astrophysical conditions, and the search for dark matter."
Proceedings from two ISSI workshops, 18-22 October 1999 and 15-19 May 2000, Bern, Switzerland
The review articles collected in this volume present a critical assessment of particle acceleration mechanisms and observations from suprathermal particles in the magnetosphere and heliosphere to high-energy cosmic rays, thus covering a range of energies over seventeen orders of magnitude, from 103 eV to 1020 eV. The main themes are observations of accelerated populations from the magnetosphere to extragalactic scales and assessments of the physical processes underlying particle acceleration in different environments (magnetospheres, the solar atmosphere, the heliosphere, supernova remnants, pulsar wind nebulae and relativistic outflows). Several contributions review the status of shock acceleration in different environments and also the role of turbulence in particle acceleration. Observational results are compared with modelling in different parameter regimes. The book concludes with contributions on the status of particle acceleration research and its future perspectives. This volume is aimed at graduate students and researchers active in astrophysics and space science. Previously published in Space Science Reviews journal, Vol. 173 Nos. 1-4, 2012.