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OSO-8 X-Ray Polarimeter and Bragg Crystal Spectrometer Observations

Published online by Cambridge University Press:  30 March 2016

R. Novick ,
H.L. Kestenbaum ,
K.S. Long ,
E.H. Silver ,
M.C. Weisskopf  and
R.S. Wolff
R. Novick
Affiliation:
Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, U.S.A.
H.L. Kestenbaum
Affiliation:
Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, U.S.A.
K.S. Long
Affiliation:
Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, U.S.A.
E.H. Silver
Affiliation:
Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, U.S.A.
M.C. Weisskopf
Affiliation:
Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, U.S.A.
R.S. Wolff
Affiliation:
Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, U.S.A.

Extract

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The OSO-8 satellite contains a focusing mosaic graphite crystal X-ray polarimeter that is oriented along the spin axis of the wheel section of the satellite. The polarimeter operates at 2.6 and 5.2 keV. Polarization in a source appears as a modulation of the counting rate at twice the satellite spin frequency. The amplitude and phase of the modulation are simply related to the polarization and position angle, respectively. Two independent polarimeters are employed, and their axes are offset by 128°. Focusing is achieved by mounting the crystals on a parabolic sector, which reduces the background without reducing the sensitivity. The low background that results from the focusing not only improves the statistical quality of the data but also substantially reduces the danger that an asymmetry in the charged particle background may produce a spurious polarization result. This is particularly important in the case of weak sources. The instrument has been described in detail elsewhere (Novick 1975); here we will briefly discuss the results obtained on the Crab Nebula, Cyg X-l, and Cyg X-2.

Type
Joint Dicussions
Information
Highlights of Astronomy , Volume 4 , Issue 1: Highlights of Astronomy. As presented at the XVIth General Assembly of the IAU, 1976 (Part I) , 1977 , pp. 95 - 97
Copyright
Copyright © Reidel 1977

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