Ariel results on extragalactic X-ray sources
Abstract
Two Ariel 5 instruments (scanning and pointed) are discussed which are designed to study weak high-galactic-latitude X-ray sources. The pointed instrument is described in detail, and a discrepancy between X-ray source counts and spatial fluctuations in the diffuse X-ray background is noted. Observed X-ray spectra are presented for the Coma, Virgo, Perseus, and Centaurus clusters of galaxies, Centaurus A, the Seyfert galaxy NGC 4151, and the quasar 3C 273. Measurements of the diffuse X-ray background are reviewed which show an excess background in the direction of the Coma cluster in comparison with the background observed in the direction of the south galactic pole. These measurements also indicate that the spectrum in both directions is not described by a simple power law. The possibility is considered that unidentified high-latitude X-ray sources may be of a completely new type which does not radiate powerfully at optical, radio, and IR wavelengths.
- Publication:
-
Philosophical Transactions of the Royal Society of London Series A
- Pub Date:
- October 1976
- Bibcode:
- 1976RSPTA.350..491S
- Keywords:
-
- Ariel 5 Satellite;
- Galactic Clusters;
- Quasars;
- Satellite-Borne Instruments;
- X Ray Sources;
- Astronomical Models;
- Uhuru Satellite;
- X Ray Astronomy;
- X Ray Spectra;
- Astrophysics;
- ARIEL 5 SATELLITE;
- GALACTIC CLUSTERS;
- QUASARS;
- SATELLITE-BORNE INSTRUMENTS;
- X RAY SOURCES;
- ASTRONOMICAL MODELS;
- UHURU SATELLITE;
- X RAY ASTRONOMY;
- X RAY SPECTRA