Kilohertz quasi-periodic oscillations or kHz QPOs are X-ray intensity variations observed in neutron star low-mass X-ray binary (LMXB) systems. In such systems, matter is transferred from a secondary low-mass star to a neutron star via the process of accretion. kHz QPOs occur on the timescale of the inner accretion flow and may carry signatures of the physics of strong gravity (c2 ~ GM/R) and possibly clues to constraining the neutron star equation of state (EOS). No model to date has been able to illuminate the origin of kHz QPOs. Spectral-timing is a set of analysis techniques useful in deriving information about the nature of physical processes occurring within the accretion flow on the timescale of the kHz QPO. We present a comprehensive study of spectral-timing products of kHz QPOs from systems where data is available in NASA’s Rossi X-ray Timing Explorer (RXTE) archive to demonstrate the promise of these techniques and to gain insights regarding the origin of kHz QPOs. Using data averaged over the entire RXTE archive, we show correlated time-lags as a function of QPO frequency and energy, as well as energy-dependent covariance spectra for the various LMXB systems where spectral-timing analysis is possible. The similarity in trends in all sources suggest a common physical origin for kHz QPOs across the population. The diferences in results between lower and upper kHz QPOs lend further support to the evidence of the differing nature of the lower and upper kHz QPOs.
|Commitee:||Cinabro, David, Miller, Jon, Pruneau, Claude|
|School:||Wayne State University|
|School Location:||United States -- Michigan|
|Source:||DAI-B 79/08(E), Dissertation Abstracts International|
|Keywords:||Kilohertz quasi–periodic oscillations, Neutron star low mass X-ray binaries, Spectral–timing analysis|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be