Teknik Bilimler Meslek Yüksekokulu / Vocational School of Technical Sciences
Permanent URI for this collectionhttps://hdl.handle.net/11727/2031
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Item Timing studies of X Persei and the discovery of its transient quasi-periodic oscillation feature(2014) Acuner, Z.; Inam, S.C.; Sahiner, S.; Serim, M.M.; Baykal, A.; Swank, J.We present a timing analysis of X Persei (X Per) using observations made between 1998 and 2010 with the Proportional Counter Array (PCA) onboard the Rossi X-ray Timing Explorer (RXTE) and with the INTEGRAL Soft Gamma-Ray Imager (ISGRI). All pulse arrival times obtained from the RXTE-PCA observations are phase-connected and a timing solution is obtained using these arrival times. We update the long-term pulse frequency history of the source by measuring its pulse frequencies using RXTE-PCA and ISGRI data. From the RXTE-PCA data, the relation between the frequency derivative and X-ray flux suggests accretion via the companion's stellar wind. However, the detection of a transient quasi-periodic oscillation feature, peaking at similar to 0.2 Hz, suggests the existence of an accretion disc. We find that double-break models fit the average power spectra well, which suggests that the source has at least two different accretion flow components dominating the overall flow. From the power spectrum of frequency derivatives, we measure a power-law index of similar to-1, which implies that, on short time-scales, disc accretion dominates over noise, while on time-scales longer than the viscous time-scales, the noise dominates. From pulse profiles, we find a correlation between the pulse fraction and the count rate of the source.Item Discovery of a glitch in the accretion- powered pulsar SXP 1062(2017) Imam, Sıtkı Cagdas; Serim, M.M.; Sahiner, S.; Cerri-Serim, D.; Baykal, A.; 0000-0003-0820-9186We present timing analysis of the accretion-powered pulsar SXP 1062, based on the observations of Swift, XMM-Newton and Chandra satellites covering a time span of about 2 yr. We obtain a phase coherent timing solution that shows that SXP 1062 has been steadily spinning down with a rate-4.29(7) x10(-14) Hz s(-1) leading to a surface magnetic field estimate of about 1.5 x 10(14) G. We also resolve the binary orbital motion of the system from X-ray data that confirms an orbital period of 656(2) d. On MJD 56834.5, a sudden change in pulse frequency occurs with Delta v = 1.28(5) x 10(-6) Hz, which indicates a glitch event. The fractional size of the glitch is Delta v/v similar to 1.37(6) x 10(-3) and SXP 1062 continues to spin-down with a steady rate after the glitch. A short X-ray outburst 25 d prior to the glitch does not alter the spin-down of the source; therefore, the glitch should be associated with the internal structure of the neutron star. While glitch events are common for isolated pulsars, the glitch of SXP 1062 is the first confirmation of the observability of this type of events among accretion-powered pulsars. Furthermore, the value of the fractional change of pulse frequency ensures that we discover the largest glitch reported up to now.