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Evidence from Quasi-Periodic Oscillations for a Millisecond Pulsar in the Low Mass X-Ray Binary 4U 0614+091We have detected quasi-periodic oscillations (QPOs) near 1 kHz from the low mass X-ray binary 4U 0614+091 in observations with RXTE. The observations span several months and sample the source over a large range of X-ray luminosity. In every interval QPOs are present above 400 Hz with fractional RMS amplitudes from 3 to 12% over the full PCA band. At high count rates, two high frequency QPOs are detected simultaneously. The difference of their frequency centroids is consistent with a constant value of 323 Hz in all observations. During one interval a third signal is detected at 328 +/- 2 Hz. This suggests the system has a stable 'clock' which is most likely the neutron star with spin period 3.1 msec. Thus, our observations of 4U 0614+091 and those of 4U 1728-34 provide the first evidence for millisecond pulsars within low-mass X-ray binary systems and reveal the 'missing-link' between millisecond radiopulsars and the late stages of binary evolution in low mass X-ray binaries. The constant difference of the high frequency QPOs sug,,ests a beat-frequency interpretation. In this model, the high frequency QPO is associated with the Keplerian frequency of the inner accretion disk and the lower frequency QPO is a 'beat' between the differential rotation frequency of the inner disk and the spinning neutron star. Assuming the high frequency QPO is a Keplerian orbital frequency for the accretion disk, we find a maximum mass of 1.9 solar mass and a maximum radius of 17 km for the neutron star.
Document ID
19990067630
Acquisition Source
Marshall Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Ford, E.
(Columbia Univ. New York, NY United States)
Kaaret, P.
(Columbia Univ. New York, NY United States)
Tavani, M.
(Columbia Univ. New York, NY United States)
Barret, D.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Bloser, P.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Grindlay, J.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA United States)
Harmon, B. A.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Paciesas, W. S.
(Alabama Univ. Huntsville, AL United States)
Zhang, S. N.
(Universities Space Research Association Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1997
Subject Category
Astrophysics
Distribution Limits
Public
Copyright
Other

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