Discovery of Two Cyclotron Resonance Scattering Features in X-ray Pulsar Cen X-3 by Insight-HXMT

• Published in: arXiv.org 2023-04
• Main Authors: Yang, W, Wang, W, Liu, Q, Chen, X, Wu, H J, Tian, P F, Chen, J S
• Format: Article
• Language: English
• Subjects: Binary stars; Broadband; Centroids; Continuum modeling; Cyclotron resonance; Luminosity; Neutron stars; Pulsars; Resonance scattering; X ray binaries; X ray spectra; X ray stars; X-ray astronomy
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2304.13283

We present the results of the neutron star X-ray binary system Cen X-3 performed by \(Insight\)-HXMT with two observations during 2017 and 2018. During these two observations, the source reached a X-ray luminosity of \(\sim 10^{38}\) erg s\(^{-1}\) from 2 -- 105 keV. The analysis of the broadband X-ray spectrum reports the presence of two cyclotron resonance scattering features (CRSFs) with the fundamental line at \(\sim\) 28 keV and the harmonic line at \(\sim 47 \) keV. The multiple lines exist by fittings with different continuum models, like the absorbed NPEX model and a power-law with high energy exponential cutoff model. This is the first time that both fundamental and harmonic lines are detected in Cen X-3. We also show evidence of two cyclotron lines in the phase-resolved spectrum of Cen X-3. The CRSF and continuum spectral parameters show evolution with the pulse profile, and the two line centroid energy ratio does not change significantly and locates in a narrow value range of \(1.6-1.7\) over the pulse phase. The implications of the discovering two cyclotron absorption features and phase-resolved spectral properties are discussed.