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Orbital period changes in Centaurus X-3Two new times of mid-X-ray eclipse for Cen X-3 are presented on the basis of pulse arrival time analyses of pointed observations with SAS 3. When combined with all other published eclipse times based on Doppler delay measurements, the results show that the 2.1d binary period is decreasing at an average rate of 1.8 x 10 to the -6th/yr. The decrease, however, is seen as having significant fluctuations about a smooth, linear decrease. The changes observed in the orbital period can be accounted for by mass loss from the system through the L2 point, although the rates required are implausibly high. It is also shown that the long-term overall orbital decay can readily be interpreted as the result of torques exerted by the tidally distorted companion star (Krzeminski's star) on the orbiting neutron star. It is noted that the inferred asynchronism between the orbital frequency and the rotation frequency of the companion star may be maintained by mass and angular momentum loss in a stellar wind or by a tidal instability related to the Darwin effect. However, this would not provide a natural explanation for any short-term deviations from a constant rate of orbital decay.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Kelley, R. L. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Rappaport, S. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Clark, G. W. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Petro, L. D. (MIT Cambridge, MA, United States)
Date Acquired
August 11, 2013
Publication Date
May 15, 1983
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 268
ISSN: 0004-637X
Subject Category
Funding Number(s)
Distribution Limits