Timing and spectral analysis of 2S 1417-624 during its 2018 outburst

Serim, Muhammed Miraç
Ozudogru, O. C.
Donmez, C. K.
Sahiner, S.
Serim, D.
Baykal, Altan
Inam, S. C.
We investigate timing and spectral characteristics of the transient X-ray pulsar 2S 1417-624 during its 2018 outburst with NICER follow up observations. We describe the spectra with high-energy cut-off and partial covering fraction absorption (PCFA) model and present flux-dependent spectral changes of the source during the 2018 outburst. Utilizing the correlation-mode switching of the spectral model parameters, we confirm the previously reported sub-critical to critical regime transitions and we argue that secondary transition from the gas-dominated to the radiation pressure-dominated disc do not lead us to significant spectral changes below 12 keV. Using the existing accretion theories, we model the spin frequency evolution of 2S 1417-624 and investigate the noise processes of a transient X-ray pulsar for the first time using both polynomial and luminosity-dependent models for the spin frequency evolution. For the first model, the power density spectrum of the torque fluctuations indicate that the source exhibits red noise component (Gamma similar to -2) within the time-scales of outburst duration which is typical for disc-fed systems. On the other hand, the noise spectrum tends to be white on longer time-scales with high timing noise level that indicates an ongoing accretion process in between outburst episodes. For the second model, most of the red noise component is eliminated and the noise spectrum is found to be consistent with a white noise structure observed in wind-fed systems.


Frequency Resolved Spectroscopy of XB 1323-619 and EXO 0748-676
Balman, Şölen (2009-09-11)
We present the frequency resolved energy spectra (FRS) of the low-mass X-ray binary dipper XB 1323-619 and EXO 0748-676 using archival XMM-Newton observations. The FRS of XB 1323-619 is well described by a single blackbody component with kT in a range 1.2-1.6 keV. We attribute this to an existing boundary layer, the likely source of the soft emission, supported by radiation pressure. We detect a different form of FRS for the frequency ranges 0.9-6 Hz and 8-30 Hz which is modeled best with a power law and a ...
Numerical analysis of long wavelength infrared HgCdTe photodiodes
Kocer, H.; Arslan, Y.; Beşikci, Cengiz (2012-01-01)
We present a detailed investigation of the performance limiting factors of long and very long wavelength infrared (LWIR and VLWIR) p on n Hg1-xCdxTe detectors through numerical simulations at 77 K incorporating all considerable generation-recombination (G-R) mechanisms including trap assisted tunneling (TAT), Shockley-Read-Hall (SRH), Auger and radiative processes. The results identify the relative strengths of the dark current generation mechanisms by numerically extracting the contribution of each G-R mec...
Viscous time scale in accreting powered pulsars and anomalous X-ray pulsars
İçdem, Burçin; Baykal, Altan; Department of Physics (2011)
In this thesis we analyse X-ray data of accretion powered low mass and high mass X-ray binaries to understand the nature of their accretion mechanisms by searching for some clues of viscous time-scales of their accretion discs, if they have, in their low frequency power density spectra created from their long-term X-ray observations, or by doing pulse timing analysis with much shorter X-ray data to detect the effects of torque fluctuations caused by the accreting material on the pulsar. The low mass and hig...
Spectral analysis of an ultraluminous X-ray source Swift J0243.6+6124
Islamov, Gubad; Baykal, Altan; Department of Physics (2021-9)
In this thesis, the spectral analysis on the first galactic ultraluminous X-ray pulsar Swift J0243.6+6124 has been carried out. This peculiar object has been firstly observed by Swift observatory during its outburst in the late 2017 – early 2018 and it is a part of a Be/X-ray binary system. Observations obtained from NuSTAR observatory have been utilized in this study. The analysis showed that the source underwent drastic changes from the beginning of its outburst stage, during the peak of the outburst and...
Recent Spin Rate Measurements of 4U 1907+09
Sahiner, S.; İNAM, SITKI ÇAĞDAŞ; Baykal, Altan (2010-08-06)
In this study, X-ray spectral and pulse timing analysis of the high mass X-ray binary (HMXB) pulsar 4U 1907+09, based on the observations with RXTE are presented. Spin rate measurements indicate a new spin-down episode with a rate close to the previous steady spin-down rate. Orbital phase resolved spectroscopy reveals that the Hydrogen column density varies through the orbit reaching to its maximum value just after periastron. A slight spectral softening with increasing luminosity is aslo observed.
Citation Formats
M. M. Serim et al., “Timing and spectral analysis of 2S 1417-624 during its 2018 outburst,” MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol. 510, no. 1, pp. 1438–1449, 2022, Accessed: 00, 2022. [Online]. Available: https://hdl.handle.net/11511/95994.