Table Of ContentX-Ray Astronomy
NATO ADVANCED STUDY INSTITUTES SERIES
Proceedings of the Advanced Study Institute Programme, which aims
at the dissemination of advanced knowledge and
the formation of contacts among scientists from different countries
The series is published by an international board of publishers in conjunction
with NATO Scientific Affairs Division
A Life Sciences Plenum Publishing Corporation
B Physics London and New York
C Mathematical and D. Reidel Publishing Company
Physical Sciences Dordrecht, Boston and London
D Behavioural and Sijthoff & Noordhoff International
Social Sciences Publishers
E Applied Sciences Alphen aan den Rijn and Germantown
U.S.A.
Series C - Mathematical and Physical Sciences
Volume 60 - X-Ray Astronomy
X-Ray Astronomy
Proceedings of the NATO Advanced Study Institute
held at Erice, Sicily, July 1-14,1979
edited by
RICCARDO GIACCONI
Harvard-Smithsonian Center for Astrophysics,
Cambridge, Mass., U.S.A.
and
GIANCARLO SETTI
University of Bologna, Laboratorio di Radioastronomia CNR,
Bologna, Italy
D. Reidel Publishing Company
Dordrecht : Holland / Boston : U .S . A. / London: England
Published in cooperation with NATO Scientific Affairs Division
Library of Congress Cataloging in Publication Data
Nato Advanced Study Institute, Erice, Italy, 1979.
X-ray astronomy.
(NATO advanced study institutes series: Series C, Mathematical and
physical sciences; v. 60)
'Published in cooperation with NATO Scientific Affairs Division.'
l. X-ray astronomy-Congresses. I. Giacconi, R. II. Setti,
Giancarlo,1935- III. North Atlantic Treaty Organization. Division of
Scientific Affairs. IV. Title. V. Series.
QB472.N37 1979 522'.686 80-23948
ISBN-13: 978-94-009-9090-6 e-ISBN-t3: 978-94-009-9088-3
DO I: tO.1 007/ 978-94-009-9088-3
Published by D. Reidel Publishing Company
P.O. Box 17,3300 AA Dordrecht, Holland
Sold and distributed in the U.S.A. and Canada
by Kluwer Boston Inc.,
190 Old Derby Street, Hingham, MA 02043, U.S.A.
In all other countries, sold and distributed
by Kluwer Academic Publishers Group,
P.O. Box 322, 3300 AH Dordrecht, Holland
D. Reidel Publishing Company is a member of the Kluwer Group
All Rights Reserved
Copyright © 1980 by D. Reidel Publishing Company, Dordrecht, Holland
Softcover reprint ofthe hardcover 1st edition 1980
No part of the material protected by this copyright notice may be reproduced or utilized
in any form or by any means, electronic or mechanical, including photocopying,
recording or by any informational storage and retrieval system,
without written permission from the copyright owner
TABLE OF CONTENTS
FOREHORD
Vll
R. Giacconi 1
X-RAY ASTRONOMY
G. Fabbiano 15
OBSERVATIONS OF SUPERNOVA RE}@ANTS WITH THE EINSTEIN OBSERVATORY
S.S. Holt 35
X-RAY SPECTRA OF SUPERNOVA RE}@ANTS
D.J. Helfand and K.S. Long 47
OBSERVATIONS OF SUPERNOVA RE}@ANTS IN THE LARGE
~1AGELLANIC
CLOUD'WITH THE EINSTEIN OBSERVATORY
P.F. Winkler, C.R. Canizares, G.W. Clark, T.H. Markert, C. Berg,
J.C. Jernigan and M.L. Schattenburg 61
HIGH RESOLUTION X-RAY SPECTROSCOPY FROM THE EINSTEIN OBSERVATORY
S. Tsuruta 73
X-RAYS FROM THE SURFACE OF NEUTRON STARS
S.S. Holt 89
X-RAY SPECTRA OF GALACTIC X-RAY SOURCES
R. Giacconi 103
STUDY OF HIGH LUMINOSITY X-RAY SOURCES IN EXTERNAL GALAXIES (H-3l)
E.P.J. van den Heuvel 115
X-RAY SOURCES AND STELLAR EVOLUTION
R. Rosner and G.S. Vaiana 129
STELLAR CORONAE FROM EINSTEIN: OBSERVATIONS AND THEORY
C. Jones 153
THE STRUCTURE AND EVOLUTION OF X-RAY CLUSTERS OF GALAXIES
vi TABLE OF CONTENTS
R. Mushotzky 171
THE X-RAY SPECTRA OF CLUSTERS OF GALAXIES
W. Forman 181
EINSTEIN OBSERVATIONS OF THE VIRGO CLUSTER
G. Chincarini 197
CLUSTER PARAMETERS
A. Cavaliere 217
MODELS OF X-RAY EMISSION FROM CLUSTERS OF GALAXIES
l. Binney 239
X-RAY STRUCTURE OF THE COMA CLUSTER FROM OPTICAL DATA
l. Binney 245
X-RAY EMISSION FROM CLUSTERS AND THE FORMATION OF GALAXIES
P. Katgert 253
RADIO PROPERTIES OF EXTRAGALACTIC X-RAY SOURCES
K.A. Pounds 273
X-RAY EMISSION FROM ACTIVE GALAXIES
H. Tananbaum 291
EINSTEIN OBSERVATIONS OF ACTIVE GALAXIES
H. Tananbaum 311
EINSTEIN OBSERVATIONS OF QUASARS
S.S. Holt 327
X-RAY ,SPECTRA OF ACTIVE GALACTIC NUCLEI
M.l. Rees 339
X-RAY EMISSION FROM GALACTIC NUCLEI
l. Bergeron 355
GAS CLOSE TO THE RADIATIVE CONTINUUM SOURCE(S) IN ACTIVE NUCLEI
M.l. Rees 363
CATEGORIES OF EXTRAGALACTIC X-RAY SOURCES
M.l. Rees 377
THE X-RAY BACKGROUND AS A PROBE OF THE MATTER DISTRIBUTION ON
VERY LARGE SCALES
R. Giacconi 385
DEEP SURVEYS WITH THE EINSTEIN OBSERVATORY
SUBJECT INDEX 399
FOREWORD
This volume contains a series of lectures presented at the 5th
Course of the International School of Astrophysics held in Erice
(Sicily) from July 1st to July 14, 1979 at the "E. l1ajorana"
Centre for Scientific Culture. The course was fully supported by
a grant from the NATO Advanced Institute Programme. It was
attended by about one hundred participants from ten countries.
Since the discovery of the first extra-solar X-ray source in
the early 1960's, X-ray astronomy has played an increasingly im
portant role in the study of the Universe, bringing new insight
to almost every field of modern astrophysics from stellar evolution
to cosmology. Generally speaking, this branch of astronomy is
concerned with the discovery, classification and study of "hot
matter" in the universe, including high energy non-thermal pheno
mena. In particular, X-ray observations appear to provide the
main, if not the only, probe to inspect regions where collapsed
objects are formed, such as the environment of neutron stars and
of black holes in the presence of matter accretion onto the ob
jects themselves. It is significant that the first candidate
black hole (Cyg X-I) has been primarily singled out by its X-ray
emission. In the same context, it is well known that one of the
fundamental problems in modern astrophysics is the understanding
of the strong activity taking place in galactic nuclei. There is
strong evidence that, whatever the final explanation of the physics
and evolution of these nuclei, one is dealing with a central power
engine basically constituted by a massive collapsed object. Here
again X-ray observations are playing a central role. Quite apart
from the physics of collapsed objects, X-ray astronomy is providing
a wealth of impressive and important data on stellar coronae,
supernova remnants, normal galaxies, quasars, radiogalaxies,
Seyfert's and other active galaxies and on the properties of the
very hot intergalactic gas which has been found in clusters of
galaxies.
A big step forward in the development of X-ray astronomy has
come from the all sky survey of UHURU, the first dedicated X-ray
satellite. The dramatic findings of UHURU have been further con
firmed and enriched by the observations of other satellites and
with balloons up to very high photon energies.
R. Giacconi and G. Setti (eds.), X-Ray Astronomy, vii-viii.
Copyright © 1980 by D. Reidel Publishing Company.
viii FOREWORD
Prior to the launch of HEAO-2 (Einstein Observatory), which
took place at the end of 1978, several hundred X-ray sources were
known. Some of these sources were identified with known classes
of extragalactic objects. However, due to the limited sensitivity
of the instruments, only the brightest objects (close by) were
found to be X-ray emitters. The Einstein Observatory with its
improved sensitivity and angular resolution (about a factor 1000)
provides the first opportunity to probe the Universe in depth and
to map the structure of extended X-ray sources.
When planning the School we had in mind, of course, that
early results from HEAO-2 (Einstein), which was due for launch
before the start of the school, may be available. We decided to
dedicate a large fraction of the programme to the extragalactic
aspects of X-ray observations on which HEAO-2 data could have the
largest impact. Therefore, only approximately one third of the
lectures have been dedicated to the discussion of galactic X-ray
sources, including the pertinent results which have become
available in the first six months of operation of the Einstein
Observatory.
In organizing the School we also had in mind the goal of
bringing together researchers and students with different
specializations in astronomy to encourage a discussion of the X-ray
results in light of the knowledge available in parallel domains
such as optical and radio, and also in view of a better exploita
tion of the potentiality of the Einstein Observatory. In this
respect it was, of course, a most opportune time to hold a NATO
Advanced Study Institute on this subject to acquaint students and
researchers, not only in X-ray astronomy, but in related fields,
with the state of the art in this important branch of astronomy
and with the new results made available in the early stages of the
life of the Einstein Observatory.
The various aspects of the subject were covered in a series
of lectures and topical seminars totalling 52 hours. Unfortunately,
for a number of reasons, it has not been possible to include in
this proceedings the texts of all the lectures which were delivered
at the School.
We wish to express our gratitude to the Scientific Affairs
Division of the North Atlantic Treaty Organization for the generous
support given to the Institute. Sincere thanks are also due to
Ms. Rhona Kamer for her patient typing of part of this book, and
to Mr. L. Baldeschi and Mr. R. Primavera for the drawing and
photographic reproduction, respectively, of a number of figures.
Special thanks are due, of course, to all lecturers and
participants who contributed so much to the success of the course,
and to Prof. A. zichichi for his hospitality at the "E. Majorana"
Centre for Scientific Culture.
Riccardo Giacconi, Harvard-Smithsonian Center for Astrophysics,
60 Garden Street, Cambridge, Mass. 02138, USA
Giancarlo Setti, University of Bologna, Istituto di Radioastronomia.
Via Irnerio 46, 40126 Bologna, Italy.
X-RA Y ASTRONOMY
Riccardo Giacconi
Harvard/Smithsonian Center for Astrophysics
Cambridge, Massachusetts USA 02138
1. INTRODUCTION AND HISTORICAL BACKGROUND
Many of the most interesting discoveries about the Universe, which
have occurred in the last few decades, have resulted from observations
of the sky in light not visible to our eye. To emphasize this point it is
only necessary to recall the discovery of the microwave background
radiation, still the most convincing evidence for the Big-Bang theory,
apart from the discovery of the recession of the galaxies 50 years ago.
The discovery of pulsars through radio observations established the
existence of neutron stars, which until then had only existed as specu
lative objects predicted by theoretical astrophysicists to be the end
point of stellar evolution for intermediate mass stars. Radio observa
tions first revealed the existence of quasi-stellar objects, now generally
believed to be objects at greater distance from us than any known, and
therefore offering clues to the early stages of the formation of galaxies
and their evolution.
Important information about the world we live in is transmitted
to us in wavelengths that we cannot perceive with our eyes, From a
scientific point of view, the reasons for this mismatch are quite clear.
Our eyes have evolved to respond to a narrow range of wavelengths
which are transmitted by the Earth's atmosphere and which are useful
for high resolution imaging even with the limited aperture detectors
(the eyes) with which we are endowed. Natural physical processes,
however, give rise to characteristic radiations in a very much wider
range of wavelengths. Molecular and atomic transitions, in which only
the most weakly bound electrons are involved, give rise to radiation in
R. Giacconi and G. Setti (eds.), X.Ray Astronomy, 1-13.
Copyright © 1980 by D. Reidel Publishing Company.
2 R.GIACCONI
the infrared and visible range of wavelength. Transitions of more
tightly bound electrons may give rise to increasingly energetic (or
shorter wavelength radiation) from ultraviolet to X-rays. Bodies at
temperatures of a few thousand degrees emit substantial fractions of
their radiation in the visible part of the spectrum, while bodies (or
better, gases) at millions of degrees temperature emit a negligible
fraction of their energy in the visible and most of it in the X-ray range
of wavelengths. Nuclear transitions typically result in gamma-ray
emission of even shorter wavelength. At the opposite end of the spectrum
we ~ind that the characteristic radiation from different physical processes
extends from the infrared through the microwave to the longest radio
wavelengths, produced by the deflection of free energetic electrons in
magnetic fields.
It has become increasingly evident in the last quarter century
that in the Universe explosive, violent processes are the norm rather
than the exception in most of the events which determine the dynamics
and evolution of stars and galaxies. To cite only an example of how this
view has changed, it is interesting to consider how the study of super
novas has convinced us that while a star uses only a few percent of its
rest mass energy in the billions of years of its evolution by nuclear
burning processes, it can liberate most of it during an abrupt gravita
tional collapse at the end of its evolutionary track. A violent ejection of
the outer shell of the star and the mixing of this material in the inter
stellar medium provide the mechanism by which the primordial hydrogen
is enriched with heavier materials. The high temperature gas which is
produced by the slowing of the ejecta into the interstellar medium emits
primarily in the X-ray range of wavelength, as does the remnant left
behind, - the pulsar.
It is a general feature of natural processes that whenever an
explosive event occurs, gases are heated to very high temperatures and/
or protons and electrons are accelerated to very high energies. The
emission of light from gases at 10 to 100 million degrees occurs
primarily in the X-ray range of wavelength, and high energy particles
emit X-rays by interaction with magnetic fields (synchrotron) or photons
(Inverse Compton).
In summary, the high energy events are dominant in the dynam
ics and evolution of the Universe. When high energy processes take place,
X-rays are emitted. X-rays furnish us, therefore, a particularly good
tool to study these processes.
