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Discovery of a cyclotron absorption line in the spectrum of the binary X-ray pulsar 4U 1538 - 52 observed by GingaA cyclotron absorption line near 20 keV has been found in the spectrum of the massive eclipsing binary X-ray pulsar 4U 1538 - 52 in observations with the Ginga observatory. The line is detected throughout the 529 s pulse cycle with a variable equivalent width that has its maximum value during the smaller peak of the two-peak pulse profile. It is found that the profile of the pulse and the phase-dependence of the cyclotron line can be explained qualitatively by a pulsar model based on recent theoretical results on the properties of pencil beams emitted by accretion-heated slabs of magnetized plasma at the magnetic poles of a neutron star. The indicated field at the surface of the neutron star is 1.7 (1 + z) x 10 to the 12th G, where z is the gravitational redshift.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Clark, George W.
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Woo, Jonathan W.
(MIT Cambridge, MA, United States)
Nagase, Fumiaki
(Institute of Space and Astronautical Science Sagamihara, Japan)
Makishima, Kazuo
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Sakao, Taro
(Tokyo, University Japan)
Date Acquired
August 14, 2013
Publication Date
April 10, 1990
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 353
ISSN: 0004-637X
Subject Category
Accession Number
Funding Number(s)
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