1. Variations of cyclotron resonant scattering features in Vela X-1 revealed with Insight-HXMT
- Author
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Liu, Q., Wang, W., Chen, X., Ding, Y. Z., Lu, F. J., Song, L. M., Qu, J. L., Zhang, S., and Zhang, S. N.
- Subjects
Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Solar and Stellar Astrophysics - Abstract
We present a detailed study of the high mass X-ray binary Vela X-1, using observations performed by Insight-HXMT in 2019 and 2020, concentrating on timing analysis and spectral studies including pulse phase-resolved spectroscopy. The cyclotron line energy is found to be at ~21-27 keV and 43-50 keV for the fundamental and first harmonic, respectively. We present the evolution of spectral parameters and find that two line centroid energy ratio E2/E1 evolved from ~2 before MJD 58900 to ~1.7 after that. The harmonic cyclotron line energy has no relation to the luminosity but the fundamental line energy shows a positive correlation with X-ray luminosity, suggesting that Vela X-1 is located in the sub-critical accreting regime. In addition, the pulse phase-resolved spectroscopy in Vela X-1 is performed. Both the CRSF and continuum parameters show strong variability over the pulse phase with the ratio of two line energies about 2 near the peak phases, and down to ~1.6 around off-peak phases. Long-term significant variations of the absorption column density and its evolution over the pulse phase may imply the existence of the clumpy wind structure near the neutron star., Comment: 10 pages, MNRAS in press
- Published
- 2022
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