Akademik Veri Yönetim Sistemi
EAS 2025, Cork, İrlanda, 23 - 27 Haziran 2025, (Yayınlanmadı)
MXB 0656-072 is a Be-type high-mass X-ray binary hosting a pulsar with a spin period of 160.7 s. The source underwent a Type II outburst in 2003, followed by a series of Type I outbursts in 2007-2008.
We investigated the timing properties and pulse variability of MXB 0656-072 throughout the Type I outbursts. The spin frequency history of the source is extended through phase-connecting year-long RXTE/PCA observations, supplemented by publicly available Fermi/GBM spin frequency measurements. Torque-luminosity analysis, based on spin frequencies and Swift/BAT daily count rates, indicates that the source's spin frequency evolution is coherent with the Ghosh-Lamb model. The magnetic field strength inferred from the torque model aligns with the field strength of the pulsar obtained from the cyclotron resonance scattering feature (CRSF). Using the torque-luminosity relation, along with magnetic field strength and Gaia distance estimates, we calculated the theoretical transition luminosity at which the accretion regime shifts from subcritical to supercritical. Our results show that this value is in agreement with the spectral transition luminosity of the source.
To investigate the timing noise characteristics of the source, we applied two novel approaches alongside the conventional Deeter method to generate high-resolution power density spectra (PDS). The new methods produced similar PDSs, confirming their effectiveness while significantly improving the time resolution. With a steepness of Γ ∼ −2, the PDSs affirm the disk-fed nature of the source.
Luminosity-sorted pulse profiles from RXTE/PCA data reveal that pulsed emission remains stable down to ~5×10³⁵ erg/s, below which pulses vanish due to ever-decreasing signal-to-noise ratio. Additionally, the results of the joint RXTE and Swift spectra analysis from the Type I outburst of MXB 0656-072, aimed at studying the evolution of CRSF, will be presented.