Hard cosmic x-ray sources
From symposium X - and gamma -ray astronomy; Madrid, Spain (11 May 1972). See CONF-720599-. A review of the observational status of x-ray sources detected in the 20 approx equal 500 keV range is presented. Of the approximately 115 sources listed in the March 1972 edition of the Uhuru to 6-keV sky survey catalog, about 15 sources have been studied in hard x rays. Most of the data have been obtained from balloons, although the OSO-3, and more recently the OSO-7, have contributed. With the exception of CEN A, the SMC, and possibly M-87, all the sources detected at higher energies are galactic and avily concentrated in the galactic plane. The Crab Nebula has been measured to about 500 keV in continuous emission and a component at the approx equal 33 ms pulsar period comprising about 20% of the total emission has been detected to ~10 MeV. Objects such as Sco-1 and Cyg-2 are characterized by an exponential spectrum, which varies over a 10 min. time scale about a factor of two, and a flatter spectrum extending to above 40 keV which exhibits independent variability. Objects such as Cyg-1 and possibly Cyg-3 have a multi-component power law spectrum extending to over 100 keV, and may vary many factors over a period of weeks. Other sources generally not yet identified with optical or radio candidates, located in the galactic center and the Centaurus/Crux region also show considerable variability, and in one case may have been detected to nearly 500 keV. Only upper limits at about 2 x 10/sup -4/ photon (cm/sup 2/ s keV)/sup - 1/ in the 20 to 50-keV range exist for most supernova remnants and extragalactic sources. (auth) From symposium X - and gamma -ray astronomy; Madrid, Spain (11 May 1972). See CONF-720599-. Some of the implications of the data on radio counterparts of x-ray sources are discussed. Data on the radio counterpart of Cyg X-3 is compared with the data on the radio star BETA Persei (Algol), to show that similar radio emission mechanisms are involved. The data for such radio stars not yet known as x-ray sources imply that such objects should be transient x-ray sources. (auth)
- Research Organization:
- Univ. of California, San Diego, La Jolla
- NSA Number:
- NSA-29-008491
- OSTI ID:
- 4426716
- Journal Information:
- Int. Astron. Union Symp., no. 55, pp. 51-73, Journal Name: Int. Astron. Union Symp., no. 55, pp. 51-73; ISSN IAUSA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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