Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"quasi-periodic oscillations"”.
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Mapping of the Quasi-periodic Oscillations at the Flank Magnetopause into the Ionosphere
… ionospheric location, area, and travel time of quasi-periodic oscillations originating from the magnetospheric flanks. This was accomplished by utilizing global and local MHD models and Tsyganenko semi-empirical magnetic field model on multiple published and four new cases believed to be caused …
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Quasi-periodic oscillations in observed and simulated temperatures, and implications for the future
… (SSA) approach that enables the study of non-periodic – so-called “quasi-periodic” oscillations (QPOs). SSA can resolve QPOs that have periods up to half the length of the record, something which is impossible using traditional Fourier analysis. All four long-term atmosphere-ocean near-surface …
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High frequency quasi-periodic oscillations in the X-ray radiation of the black hole binary GRS 1915+105
… cycle, which is selected for its high frequency quasi-periodic oscillations (HFQPOs) and recurring double-peak flare in the light curve. We investigate the primary properties of the 82 p-type observations collected by RXTE. The range in flare recurrence time () is 33.73 s < T < 122.49 s, with <> …
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Spectral changes during the 0.1-4 Hz quasi-periodic oscillations in the black hole X-ray binary XTE J1550-564
… thesis, we describe the analysis of 0.1-4 Hz quasi-periodic oscillations (QPOs) of the black hole X-ray binary XTE J1550-564 using data obtained with the Rossi X-ray Timing Explorer (RXTE) satellite. Data from 13 consecutive observations spanning eight days were included in this analysis. By …
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Alfven-Rossby Waves in Rotating Magnetized Stars
… and explained the existence of very long-period quasi-periodic oscillations.
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Rapid oscillations in cataclysmic variable stars
Rapid quasi-coherent oscillations were detected in the optical light curves of 24 cataclysmic variable stars (CVS). In 12 of these systems (TU Men, WW Cet, HX Peg, BP CrA, BR Lup, HP Nor, AG Hya, TW Vir, PU CMa, V426 Ooph, V1193 Ori, and CR Boo) for the first time. The results contribute to the …
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A spectroscopic analysis of the eclipsing Nova-like EC21178-54
… reveal that this system is a rich source of quasi-periodic oscillations (QPOs), dwarf nova oscillations (DNOs) and the other type of periodic oscillations called longer period dwarf nova oscillations (lpDNOs). Its light curve shows a deep symmetrical V-shaped primary eclipse, and its spectra …
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X-ray power density spectra of black hole binaries : a new deadtime model for the RXTE PCA
… systems, power density spectra reveal coherent oscillations for those sources that are pulsars, while quasi-periodic oscillations over a wide range of frequencies (0.01 to 1300 Hz) are used to identify subclasses and to probe the details of accretion physics. For black hole binaries, the power …
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Time-dependent Accretion Flows onto Black Holes
… variable. The characteristic frequency of the oscillations is near to the local keplerian orbital frequency, which makes them a potential candidate for the high-frequency quasi-periodic oscillations present in the X-ray light-curves of BHXB's.
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Radiation transport around Kerr black holes
… have shown the existence of high frequency quasi-periodic oscillations (HFQPOs) in a number of black hole binary systems. In Chapter 3, we employ a simple \hot spot" model to explain the position and amplitude of these HFQPO peaks. The power spectrum of the periodic X-ray light curve …
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Magnetospheres of neutron stars accreting from disks
… galactic bulge X-ray sources that display quasi-periodic oscillations in intensity. These QPO sources are thought by some to be weakly magnetic neutron stars accreting from disks. In constructing these magnetospheric models, I assume that the magnetic field is static and axisymmetric about …
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Mass transfer and accretion in the eccentric neutron-star binary Circinus X-1
… state: On the horizontal branch, quasi-periodic oscillations (QPOs) in the X-ray intensity shift in frequency from 1.3 to 35 Hz. On the normal branch, a different QPO occurs at about 4 Hz. On the flaring branch only strong aperiodic variability occurs. I modeled the evolution of …
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Spectral-Timing Observations of Disk-Jet Coupling in Black Hole X-ray Binaries
… state. I also discover one of the most coherent quasi-periodic oscillations, and find an interplay between heartbeats and iron emission/absorption line. These results lead to new insights into the physical nature of exotic variabilities and accretion disk instability.
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A spectral and timing study of MAXI J1820+070 during outburst
… keV. We identify the presence and evolution of quasi-periodic oscillations and quantify them through Lorentzian curve fitting. Additionally, we identified hard and soft time lags, varying in amplitude and frequency during the outburst. Together, the spectral and timing results suggest a QPO …
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The X-ray and gamma-ray sky - Temporal, spectral and triangulation techniques for the characterization and localization of sources in High Energy Astrophysics
… The timing analysis shows features, such as Quasi-Periodic Oscillations, at around 2 Hz, compatible with a Black Hole Transient in a hard state. Accreting Millisecond X-ray Pulsars (AMXPs) are a subclass of NS LMXBs in which the NS shows X-ray pulsations at periods shorter than 10 …
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The accretion process in neutron-star low-mass X-ray binaries
… state with frequent occurrences of kilohertz quasi-periodic oscillations (kHz QPOs), the accretion disk appears to be truncated at larger radii than in other parts of the soft state where the disk is presumably truncated at the ISCO. Thus the production of kHz QPOs in accreting NSs should be …
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Compact Objects In Relativistic Theories Of Gravity
… of the scalar field on the crustal torsional oscillations of neutron stars, which have been associated to quasi-periodic oscillations in the x-ray spectra in the aftermath of giant flares. We show that the presence of the scalar field has an influence on the thickness of the stellar crust, and …
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The optical polarization variability of the blazar PKS 2155 304
… revealed, for the first time, evidence of quasiperiodic oscillations in the optical polarization of a blazar. A periodogram analysis of the polarized flux revealed the existence of two periodic components at ≥ 13 minutes and ≥ 30 minutes. The oscillations can be explained by turbulence …