Abstract
view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An X-Ray Observation of the Crab Nebula. Haymes, Robert C. Abstract We have conducted a balloon measurement of the spectrum of the hard x rays from the Crab Nebula. The instrument is a well-type scintillation counter arranged to rej ect charged particles and to respond only to photons with energies between 23 and 455 keV. A 128-channel pulse height analysis is performed on such photons. The energy resolution is 27%, full width half- maximum, at 50 keV. The sensitive area is 75 cm2, and the opening half-angle of the instrument is 3 degrees. It was aimed at the Crab for 320 min, and it was also pointed away to measure the background spectrum. The pressure-altitude of the balloon varied between 4.35 and 6.0 mbar. A correction for absorption of the difference spectrum to the top of the atmosphere results in a spectrum that is in good agreement with other measurements where they overlap. We find that the differential photon flux between 30 and 75 keV may be approximated by a single exponential, 1.1 exp (-.1 19E) photons cm-2 sec-1 keV-1, where E is expressed in keV. This expression is valid over two orders of magnitude in flux. Power law spectra may only be fitted over narrower energy intervals. Synchroton radiation results in a power- law dependence. Thermal bremmstrahlung, however, produces an exponential spectrum. The slope of the observed exponential corresponds to a temperature of 1x108 0K. The research was supported in part by the Air Force Office of Scientific Research, Office of Aero- space Research, United States Air Force, under Grant Number AF-AFOSR-858-65. Publication: The Astronomical Journal Pub Date: February 1966 DOI: 10.1086/110106 Bibcode: 1966AJ.....71R.387H full text sources ADS |
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