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Kilohertz Quasi-Periodic Oscillation and Atoll Source States in 4U 0614+09

Méndez, M. and van der Klis, M. and van Paradijs, J. and Lewin, W. H. G. and Lamb, F. K. and Vaughan, B. A. and Kuulkers, E. and Psaltis, D. (1997) Kilohertz Quasi-Periodic Oscillation and Atoll Source States in 4U 0614+09. Astrophysical Journal Letters, 485 (1). L37-L40. ISSN 2041-8205.

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We report three RXTE/PCA observations of the low-mass X-ray binary 4U 0614+09. They show strong ( ~30% rms) band-limited noise with a cutoff frequency varying between 0.7 and 15 Hz in correlation with the X-ray flux, fX. We observe two nonsimultaneous 11%-15% (rms) kHz peaks near 728 and 629 Hz in the power spectra of two of our observations when fX ~ 10-9 ergs cm-2 s-1 (2-10 keV) but find no quasi-periodic oscillations (QPOs; <6% rms) when fX is half that. We suggest that count rate may not be a good measure for dot M even in sources as intrinsically weak as 4U 0614+09 and that QPO frequency and noise cutoff frequency track dot M more closely than count rate. The QPO increases in rms amplitude from 11% ± 1.3% at 3 keV to 37% ± 12% at 23 keV; the fractional amplitude of the band-limited noise is energy independent. This suggests different sites of origin for these two phenomena. The spectrum of the oscillating flux roughly corresponds to a black body with temperature 1.56 ± 0.2 keV and radius 500 ± 200 m (other models fit as well), which might indicate that the oscillations originate at a small region on the neutron star surface.

Item Type:Article
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URLURL TypeDescription
van der Klis, M.0000-0003-0070-9872
Lamb, F. K.0000-0002-3862-7402
Additional Information:© 1997. American Astronomical Society. Received 1997 March 21, accepted for publication 1997 May 30. This work was supported in part by the Netherlands Organization for Scientific Research (NWO) under grant PGS 78-277 and by the Netherlands Foundation for Research in Astronomy (ASTRON) under grant 781-76-017. M. M. is a fellow of the Consejo Nacional de Investigaciones Cientıficas y Te´cnicas de la Republica Argentina. W. H. G. L. acknowledges support from the National Aeronautics and Space Administration. J. v. P. acknowledges support from the National Aeronautics and Space Administration through contract NAG5-3269. F. K. L. acknowledges support from NSF, through grant AST 93-15133, and NASA, through grant 5-2925.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Non-Subject Keywords:accretion, accretion disks; stars: individual (4U 0614+091); stars: neutron; X-rays: stars
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Space Radiation Laboratory1997-45
Issue or Number:1
Record Number:CaltechAUTHORS:20141203-092934218
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52313
Deposited By: Deborah Miles
Deposited On:03 Dec 2014 20:39
Last Modified:09 Mar 2020 13:19

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