X-ray flux and pulse frequency changes of three high mass X-ray binary pulsars: Vela X-1, GX 301-2 and OAO 1657-415

Inam, SC
Baykal, Altan
Using archival BATSE (Burst and Transient Source Experiment) 20-50 keV band X-ray flux and pulse frequency time series, we look for correlations between torque, luminosity and specific angular momentum for three high mass X-ray binary pulsars Vela X-1, GX 301-2 and OAO 1657-415. Our results show that there is no correlation between pulse frequency derivative and flux which may be an indication of the absence of stable prograde accretion disk. From the strong correlation of specific angular momentum and torque, we conclude that the accretion geometry changes continuously as suggested by the hydrodynamic simulations (Blondin et al. 1990).


The torque and X-ray flux changes of OAO 1657-415
Baykal, Altan (1997-03-01)
Combining previously published pulse frequencies and BATSE measurements, we estimate the noise strengths (or power density estimates) of angular accelerations by using the root mean square residuals of angular velocity time series of OAO 1657-415 and present the power spectra. The statistical interpretation of the angular velocity fluctuations is consistent with a random walk model. In order to investigate the short term angular velocity fluctuations in detail, a structure function analysis is applied for a...
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 ...
Baykal, Altan; DEETER, JE; SCOTT, DM (1993-11-15)
We calculate the power density spectrum of fluctuations in the X-ray turn-on times of Her X-1, including new data which extend the X-ray and optical flux observations to a span of over 20 yr with 221 distinct 35-d high-low flux cycles. If we assume that turn-on times define the period of the 35-d clock, this statistical interpretation of turn-on behaviour is consistent with a white-noise process in the first derivative of the 35-d phase fluctuations (or a random walk in clock phase). We discuss the implicat...
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.
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. (2022-02-01)
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 ...
Citation Formats
S. Inam and A. Baykal, “X-ray flux and pulse frequency changes of three high mass X-ray binary pulsars: Vela X-1, GX 301-2 and OAO 1657-415,” ASTRONOMY & ASTROPHYSICS, pp. 617–623, 2000, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/53893.