Investigation of quasi-periodic noise features in x-persei

Acuner, Zeynep
In this thesis, timing and spectral properties of the Be type X-ray binary XPersei based on Rossi X-Ray Timing Explorer (RXTE) have been presented. Results of the power spectral analysis of RTXE data show QPO features detected between ⇠ 0.1-0.4 Hz which are reported for the first time. Another significant property of X-Per’s power spectra is the time dependent excess that can be observed between 0.01-0.08 Hz throughout the observations. These power excesses are interpreted as an inherent feature of source’s accretion. Besides this, hardness properties of the source have been carefully examined, which gives an insight to the QPO generation process. It has been concluded that QPO generation is most efficient during time intervals with soft photon abundance where highest QPO frequencies are observed (3-7/7-10 keV). Although X-Per’s general accretion pattern is that of wind accretion which matches with the predictions of Quasi-Spherical Acretion Theory, these investigations also imply the existence of an accretion disk that exists throughout the RXTE observations around the pulsar 4U 0352+309. Values estimated for inner Keplerian radius and magnetic field hence the magnetospheric radius clearly indicate that the accretion disk and the magnetic field closely interact which can be considered as the source of aperiodic variability.


Determining the asymmetry in supernova explosions by studying the radial velocities of OB runaway stars
Dinçel, Baha; Yerli, Sinan Kaan; Ankay, Aşkın; Department of Physics (2012)
Understanding the asymmetry in core collapse supernova explosions is pointed out by various astrophysicists as it is the key factor in determining the observational properties of the pulsars. The initial kick given by the ex- plosion to the pulsar affects its spin period and space velocity. Up to now, although the observations do not show a direct relation between the observational features of the pulsar and its space velocity, they show a clear relation between the spin period and the magnetic field streng...
Investigation of photovoltaic properties of amorphous InSe thin film based Schottky devices
Yilmaz, K.; Parlak, Mehmet; Ercelebi, C. (IOP Publishing, 2007-12-01)
In this study, device behavior of amorphous InSe thin films was investigated through I-V, C-V and spectral response measurements onto SnO2/p-InSe/metal Schottky diode structures. Various metal contacts such as Ag, Au, Al, In and C were deposited onto amorphous p-InSe films by the thermal evaporation technique. The best rectifying contact was obtained in a SnO2/p-InSe/Ag Schottky structure from I-V measurements, while the Au contact had poor rectification. Other metal contacts (Al, In and C) showed almost oh...
Theoretical investigation of intersubband nonlinear optical rectification in AlxlGa1-xlAs/GaAs/AlxrGa1-xrAs asymmetric rectangular quantum wells
Karabulut, Ibrahim; Atav, Uelfet; Safak, Haluk; Tomak, Mehmet (Wiley, 2007-09-01)
In this study, a theoretical investigation of intersubband nonlinear optical rectification in Alx1Ga1-x1As/ GaAs/AlxrGa1-xrAs asymmetric rectangular quantum wells is presented. The electronic states in the asymmetric rectangular quantum well are described within the framework of the envelope function approach including the effects of band nonparabolicity and the effective mass mismatch. The nonlinear optical rectification is calculated using the density matrix formalism. It is found that the nonlinear optic...
Investigation of structural, electronic, magnetic and lattice dynamical properties for XCoBi (X: Ti, Zr, Hf) Half-Heusler compounds
Surucu, Gokhan; IŞIK, MEHMET; CANDAN, ABDULLAH; Wang, Xiaotian; Güllü, Hasan Hüseyin (Elsevier BV, 2020-06-15)
Structural, electronic, magnetic, mechanical and lattice dynamical properties of XCoBi (X: Ti, Zr, Hf) Half-Heusler compounds have been investigated according to density functional theory and generalized gradient approximation. Among alpha, beta and gamma structural phases, gamma-phase structure has been found as the most stability characteristics depending on the calculated formation enthalpies, energy-volume dependencies and Cauchy pressures. Energy-volume plots of possible magnetic orders of gamma-phase ...
Estimation of Articulatory Trajectories Based on Gaussian Mixture Model (GMM) With Audio-Visual Information Fusion and Dynamic Kalman Smoothing
ÖZBEK, İbrahim Yücel; Hasegawa-Johnson, Mark; Demirekler, Mübeccel (Institute of Electrical and Electronics Engineers (IEEE), 2011-07-01)
This paper presents a detailed framework for Gaussian mixture model (GMM)-based articulatory inversion equipped with special postprocessing smoothers, and with the capability to perform audio-visual information fusion. The effects of different acoustic features on the GMM inversion performance are investigated and it is shown that the integration of various types of acoustic (and visual) features improves the performance of the articulatory inversion process. Dynamic Kalman smoothers are proposed to adapt t...
Citation Formats
Z. Acuner, “Investigation of quasi-periodic noise features in x-persei,” M.S. - Master of Science, Middle East Technical University, 2014.