The Universe in Gamma Rays

417 Pages·2001·15.748 MB·English

by  Volker Schönfelder (auth.), Prof. Volker Schönfelder (eds.)

ASTRONOMY AND
~
ASTROPHYSICS LIBRARY
LIBRARY
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Physics and Astronomy
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Volker Schonfelder (Ed.)
The Universe
in Gamma Rays
With 141 Figures Including 28 Color Figures
, Springer
Prof. Volker Schonfelder (Ed.)
Max-Planek-Institut fiir extraterrestrisehe Physik
Giessenbaehstrasse
85748 Garehing
Germany
Cover picture: All-sky map obtained by COMPTEL on the Compton Gamma-Ray Observatory in the light of the
1.809 MeV gamma-ray line from radioactive 26 AL.
Library of Congress Cataloging-in-Publication Data applied for.
Die Deutsche Bibliothek -CIP-Einheitsaufnahme
The universe in gamma rays: with 4 tables / Volker Schonfelder (ed.).
(Astronomy and astrophysics library)
(Physics and astronomy online library)
ISBN 978-3-642-08745-5 ISBN 978-3-662-04593-0 (eBook)
DOI 10.1007/978-3-662-04593-0
ISSN 0941-7834
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Preface
This is an ideal time to write a book about the Universe as seen in 'Y-rays.
During the last decade, 'Y-ray astronomy has experienced a period of fruition.
The first-ever complete sky surveys have been produced by the Compton
Gamma Ray Observatory, with a large number of exciting discoveries; the
more than 25-year-old puzzle of the origin of 'Y-ray bursts is on its way to
being solved; and ground-based 'Y-ray astronomy at TeV energies has achieved
its first break-through. We have learned that the 'Y-ray Universe is violent,
energetic and variable. The recent results in this field have attracted scientists
from all branches of astronomy and astrophysics. Gamma-ray astronomy has
now become an integrated part of astronomy.
This book summarizes recent achievements. The anticipated readers are
students, graduates, astronomers and astrophysicists in general, and experts
working in the field. The book was written by the team of 'Y-ray astronomers
at the Max-Planck-Institut fUr extraterrestrische Physik in Garching, Ger
many. By means of many working sessions we have tried to produce a coherent
description of the entire field of 'Y-ray astronomy. The book was written in
1998 and early 1999, and reflects the state of the research field up to that
date.
The distinction between X-ray and 'Y-ray astronomy is not well defined
(the classical definition of X-radiation being produced in atomic shells and
'Y-radiation in atomic nuclei does not make sense in astronomy). In this book,
we consider 'Y-ray astronomy to begin at photon energies around 500 keY.
Sometimes lower energy photons are considered as well, if this turns out to
be important.
Following the introduction, which is devoted to the history of 'Y-ray as
tronomy, the book starts with two chapters describing the processes of cosmic
'Y-ray production and absorption and the basic principles of instrumentation
used in 'Y-ray astronomy. The main part of the book (starting with Chap. 4)
deals with the astronomical results and their interpretation. Those readers
who are not interested in the instrumentation and/or the production pro
cesses, may skip Chaps. 2 and 3. The collection of references and the subject
index at the end of the book may be a helpful starting point for readers who
want to go deeper into this new research field.
VI Preface
Many friends and colleagues have given us their support in improving the
book. We want to thank particularly Drs. Peter von Ballmoos, Bernd Aschen
bach, Edward L. Chupp, Dieter Hartmann, Felix Aharonian, Werner Becker,
Markus Bottcher, Karen Brazier, Andreas von Kienlin, Stefan Pliischke, John
Mattox, Bonnard Teegarden, David J. Thomson, and Jorn Wilms, who all
made valuable suggestions on early drafts of the manuscript. We are also
indebted to Mrs. Helga Haber for her supporting role in fulfilling the many
editorial tasks and to Dr. Robert Georgii, who took great care of all technical
editorial matters.
As editor of this book, I would like to take this opportunity to express
my special gratitude to my wife, Barbel, who has provided essential support
and encouragement to me throughout my entire professional life.
Garching, May 2001 Volker Schon/elder
Contents
1 Introduction
Volker Schonfelder 1
References .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Gamma-Ray Production and Absorption Processes
Roland Diehl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1 Introduction to Astronomy with Gamma-Rays. . . . . . . . . . . . . . . . . 9
2.2 Production Processes ....................................... 12
2.2.1 Charged Particles in Strong Electric or Magnetic Fields. . .. 13
2.2.2 Inverse Compton Scattering. . . . . . . . . . . . . . . . . . . . . . . . . . .. 16
2.2.3 Nuclear Transitions ................................... 17
2.2.4 Decays and Annihilation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18
2.2.5 Charged particles bound in strong magnetic fields. . . . . . . .. 19
2.3 Gamma-Ray Interactions, Absorption Processes. . . . . . . . . . . . . . .. 20
2.4 Cosmic Gamma-Ray Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21
2.5 The Fate of Gamma-Rays Between Source and Detector. . . . . . . .. 23
References ..................................................... 25
3 Instruments
Giselher Lichti and Robert Georgii ......... , . . . . . . . . . . . . . . . . . . . . .. 27
3.1 Detection of Gamma-Rays from Space. . . . . . . . . . . . . . . . . . . . . . . .. 27
3.1.1 The Opaqueness of the Atmosphere. . . . . . . . . . . . . . . . . . . .. 27
3.1.2 The Low Cosmic Gamma-Ray Fluxes. . . . . . . . . . . . . . . . . . .. 27
3.1.3 The Background of Gamma-Ray Telescopes. . . . . . . . . . . . .. 28
3.2 Gamma-Ray Detection Techniques ..... , ........ , . . . . . . . . . . . .. 31
3.2.1 Scintillation Techniques ......... , ........ , . . . . . . . . . . . .. 31
3.2.2 Solid-State Detectors ........... , ........ , . . . . . . . . . . . .. 35
3.2.3 Spark Chambers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37
3.2.4 Cherenkov Detectors .................... , . . . . . . . . . . . .. 38
3.2.5 Drift Chambers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39
3.3 Gamma-Ray Telescopes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39
3.3.1 The Chopper Technique ............................... 41
3.3.2 The On/Off Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41
3.3.3 Compton Telescopes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 50
VIII Contents
3.3.4 Pair-Tracking Telescopes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 56
3.3.5 Air-Shower Detection Techniques ....................... 60
3.3.6 Gamma-Ray Burst Instruments. . . . . . . . . . . . . . . . . . . . . . . .. 65
3.4 Specific Calibration and Data-Analysis Problems. . . . . . . . . . . . . .. 66
3.5 Current Developments and Future Instrumentation ............. 68
3.5.1 Advanced Compton Telescopes ......................... 68
3.5.2 Advanced Pair-Production Telescopes ................... 71
3.5.3 The Gamma-Ray Lens. . .... . . ... . . . ... . . ... . . ... . . .... 71
References ..................................................... 73
4 Summary of the Gamma-Ray Sky
Volker Sch6nfelder .............................................. 77
4.1 Introduction............................................... 77
4.2 All-Sky Maps in the MeV-GeV Region. ... . . . . ... . ... . . .. . . . .. 78
4.3 The Sub-MeV Domain ...................................... 80
4.4 The TeV Gamma-Ray Sky. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 86
4.5 Gamma-Ray Bursts. . ... . . . .. . . . .. . . . ... . . . . ... . ... . . . .. . . .. 87
References ..................................................... 89
5 The Sun as a Gamma-Ray Source
Erich Rieger and Gerhard Rank .................................. 91
5.1 Introduction............................................... 91
5.2 Production of Gamma-Rays and Neutrons. . . . . . . . . . . . . . . . . . . .. 94
5.2.1 Flare Scenario. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 94
5.2.2 Conditions for Gamma-Ray Production
in the Solar Flare Environment . . . . . . . . . . . . . . . . . . . . . . . .. 95
5.3 The Solar Flare Gamma-Ray Spectrum ........................ 100
5.3.1 The Observed Gamma-Ray Spectrum ................... 100
5.3.2 Spectral Analysis ..................................... 103
5.4 Temporal History of Gamma-Ray Emission During Flares ....... 111
5.4.1 Evolution of Flares: Impulsive and Gradual Emission ...... 111
5.4.2 Timing of Electron and Ion Interactions ................. 113
5.4.3 Extended Gamma-Ray Emission ....................... 114
5.5 Acceleration Mechanisms .................................... 116
5.5.1 Theoretical Considerations of Particle Acceleration ........ 116
5.5.2 Acceleration Models for Solar Flares ..................... 119
5.6 Conclusions ................................................ 121
5.6.1 Our Current Understanding of the Flare Phenomenon ..... 121
5.6.2 Expectations for the Future ............................ 122
References ..................................................... 123
Contents IX
6 Gamma-Ray Pulsars
Gottfried Kanbach .............................................. 127
6.1 Introduction ............................................... 127
6.1.1 Radio Pulsars: Discovery of Rotating Neutron Stars ....... 127
6.1.2 The Formation of Neutron Stars
and Their Basic Properties ............................. 128
6.1.3 Expectation of High-Energy Phenomena
Around Young Pulsars ................................. 131
6.1.4 Early History of the Observation of Gamma-Ray Pulsars ... 134
6.2 Current Observational Results of High-Energy Emission
from Pulsars ............................................... 135
6.2.1 Detections of High-Energy Pulsars ...................... 135
6.2.2 Gamma-Ray Searches and Limits for Other Radio Pulsars .. 138
6.2.3 Light Curves of Gamma-Ray Pulsars .................... 140
6.2.4 Multi-Wavelength Light Curves ......................... 141
6.2.5 Spectra of Electromagnetic Radiation from Pulsars ........ 143
6.2.6 Phase-Dependent Gamma-Ray Spectra of Pulsars ......... 147
6.2.7 Pulsar Luminosities and Gamma-Ray Efficiencies ......... 147
6.2.8 Search for Identification of Other Gamma-Ray Sources .... 149
6.3 Theory of Pulsar High-Energy Emissions ...................... 150
6.3.1 Acceleration Zones and Production of Relativistic Particles. 150
6.3.2 Radiation and Propagation Processes .................... 151
6.3.3 Field Line Geometries, Beaming and Light Curves ........ 153
6.3.4 Spectra, Luminosities and Efficiencies ................... 154
References ..................................................... 156
7 X-Ray Binaries as Gamma-Ray Sources
Werner Collmar ................................................ 159
7.1 The Nature of X-Ray Binaries ................................ 159
7.2 High-Energy Emission from Black-Hole Systems ................ 161
7.2.1 Time Variability ...................................... 164
7.2.2 Energy Spectra ....................................... 168
7.2.3 Interpretation ........................................ 171
7.3 High-Energy Emission from Neutron-Star Binaries
and Cataclysmic Variables ................................... 175
7.4 Peculiar Cases ............................................. 177
7.4.1 CygnusX-3 ................................., ......... 177
7.4.2 Centaurus X-3 ........................................ 178
7.5 TeV Observations of X-Ray Binaries .......................... 179
7.6 Summary and Conclusions ................................... 181
References ..................................................... 183
X Contents
8 Continuum Gamma Ray Emission
from Supernova Remnants
Anatoli Iyudin and Gottfried Kanbach . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 185
8.1 Introduction ............................................... 185
8.1.1 Shell-type SNRs ...................................... 188
8.1.2 Crab-like SNRs ....................................... 188
8.1.3 Composite SNRs ...................................... 189
8.2 Continuum Gamma Rays from SNR .......................... 191
8.3 SNRs and Particle Acceleration .............................. 197
8.4 Discussion and Outlook ..................................... 200
8.5 Conclusions ................................................ 204
References ..................................................... 204
9 Diffuse Galactic Continuum Gamma-Rays
Andrew W. Strong and Igor V. Moskalenko ........................ 207
9.1 Introduction ............................................... 207
9.2 Theoretical Background ..................................... 207
9.2.1 Basic Processes of Gamma-Ray Production ............... 207
9.2.2 Cosmic-Rays ......................................... 210
9.2.3 Galactic Structure .................................... 213
9.3 Gamma-Ray Observations ........................ '. .......... 215
9.4 Interpretation ............................................. 217
9.4.1 Longitude and Latitude Distributions .................... 218
9.4.2 Spectra of the Inner Galaxy ............................ 219
9.4.3 Implications for Cosmic Rays ........................... 221
9.4.4 Multi-component Fitting Approach ...................... 223
9.4.5 Implications for ISM: H /CO Calibration ................ 225
2
9.4.6 Local Clouds ......................................... 227
9.4.7 Contribution of Unresolved Sources to 'Diffuse' Emission ... 227
9.4.8 High Latitudes ....................................... 227
9.5 Global Gamma-Ray Properties of Our Galaxy .................. 228
9.6 Extragalactic Objects ....................................... 229
9.6.1 The Large and Small Magellanic Clouds ................. 229
9.6.2 Other Galaxies ....................................... 230
References ..................................................... 230
10 Nucleosynthesis
Roland Diehl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
10.1 Introduction ............................................... 233
10.2 Nucleosynthesis Processes ................................... 236
10.3 Sites of Nucleosynthesis ..................................... 242
10.3.1 Hydrostatic Nuclear Burning ........................... 242
10.3.2 Explosive Nucleosynthesis .............................. 244
10.3.3 Other Nucleosynthesis Sites ............................ 252