@article{af7a891917ce4c0bbe924e899457b315,
title = "The beat-frequency interpretation of kilohertz quasi-periodic oscillations in neutron star low-mass X-ray binaries",
abstract = "Pairs of quasi-periodic oscillations (QPOs) at kilohertz frequencies are a common phenomenon in several neutron-star low-mass X-ray binaries. The frequency separation of the QPO peaks in the pair appears to be constant in many sources and directly related to the neutron star spin frequency. However, in Sco X-1 and possibly in 4U 1608252, the frequency separation between the QPO peaks decreases with increasing inferred mass accretion rate. We show that the currently available Rossi X-Ray Timing Explorer data are consistent with the hypothesis that the peak separations in all sources vary by amounts similar to the variation in Sco X-1. We discuss the implications for models of the kilohertz QPOs.",
keywords = "Accretion, Accretion disks, Stars: neutron, X-rays: stars",
author = "Dimitrios Psaltis and Mariano M{\'e}ndez and Rudy Wijnands and Jeroen Homan and Jonker, {Peter G.} and {Van Der Klis}, Michiel and Lamb, {Frederick K.} and Erik Kuulkers and {Van Paradijs}, Jan and Lewin, {Walter H.G.}",
note = "Funding Information: 1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138; dpsaltis@cfa.harvard.edu. 2 Astronomical Institute “Anton Pannekoek,” University of Amsterdam and Center for High Energy Astrophysics, Kruislaan 403, NL-1098 SJ Amsterdam, The Netherlands; mariano@astro.uva.nl, rudy@astro.uva.nl, homan@ astro.uva.nl, peterj@astro.uva.nl, michiel@astro.uva.nl, jvp@astro.uva.nl. 3 Facultad de Ciencias Astron{\'o}micas y Geofisicas, Universidad Nacional de la Plata, Pasco del Bosque S/N, 1090 La Plata, Argentina. 4 Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720. 5 Departments of Physics and Astronomy, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, IL 61801; f-lamb@uiuc.edu. 6 Astrophysics, University of Oxford, Nuclear and Astrophysics Laboratory, Keble Road, Oxford, OX1 3RH, England, UK; e.kuulkers1@physics .oxford.ac.uk. 7 Department of Physics, University of Alabama at Huntsville, Huntsville, AL 35899. 8 Department of Physics and Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139; lewin@space.mit.edu. Publisher Copyright: {\textcopyright} 2000. The American Astronomical Society. All rights reserved.",
year = "1998",
month = jul,
day = "1",
doi = "10.1086/311455",
language = "English (US)",
volume = "501",
pages = "L95--L99",
journal = "Astrophysical Journal Letters",
issn = "2041-8205",
publisher = "IOP Publishing Ltd.",
number = "1",
}