629 research outputs found
Advances in high energy astronomy from space
Observational techniques, derived through space technology, and examples of what can be learned from X-ray observations of a few astronomical objects are given. Astronomical phenomena observed include the sun, stellar objects, and galactic objects
A high energy astronomy overview
A technology assessment of extrasolar X-ray astronomy is presented. The role and significance of the Einstein Observatory is described
X-ray reflection collimator adapted to focus X-radiation directly on a detector Patent
X ray collimating structure for focusing radiation directly onto detecto
Axial Anomaly in the Presence of the Aharonov-Bohm Gauge Field
We investigate on the plane the axial anomaly for euclidean Dirac fermions in
the presence of a background Aharonov--Bohm gauge potential. The non
perturbative analysis depends on the self--adjoint extensions of the Dirac
operator and the result is shown to be influenced by the actual way of
understanding the local axial current. The role of the quantum mechanical
parameters involved in the expression for the axial anomaly is discussed. A
derivation of the effective action by means of the stereographic projection is
also considered.Comment: 15 pages, Plain.TeX, Preprint DFUB/94 - 1
A FIRST DETERMINATION OF THE SURFACE DENSITY OF GALAXY CLUSTERS AT VERY LOW X--RAY FLUXES
We present the first results of a serendipitous search for clusters of
galaxies in deep ROSAT-PSPC pointed observations at high galactic latitude. The
survey is being carried out using a Wavelet based Detection Algorithm which is
not biased against extended, low surface brightness sources. A new
flux--diameter limited sample of 10 cluster candidates has been created from
surveyed area. Preliminary CCD observations have revealed
that a large fraction of these candidates correspond to a visible enhancement
in the galaxy surface density, and several others have been identified from
other surveys. We believe these sources to be either low--moderate redshift
groups or intermediate to high redshift clusters. We show X-ray and optical
images of some of the clusters identified to date. We present, for the first
time, the derived number density of the galaxy clusters to a flux limit of (0.5--2.0 keV). This extends the -- of previous cluster surveys by more than one decade in flux.
Results are compared to theoretical predictions for cluster number counts.Comment: uuencoded compressed Postscript, 7 pages including 4 figures.
Accepted for publication in Ap. J. Letters
Results of a Sounding Rocket experiment to study celestial X-ray sources Final report
Sounding rocket experiment to study celestial X-ray source
A program of X-ray astronomy from sounding rocket Final report
X-ray astronomy from sounding rocket
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