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

Abstract

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.

8 pages, MNRAS, 2023, 519, 5402-5409

References in corpus (10)

• Thermal and Bulk Comptonization in Accretion-Powered X-Ray Pulsars
• The ephemeris, orbital decay, and masses of 10 eclipsing HMXBs
• A model for cyclotron resonance scattering features
• Pulse phase resolved analysis of the HMXB Cen X-3 over two binary orbits
• A new radio census of neutron star X-ray binaries
• The first cyclotron harmonic of 4U 1538-52
• Long-term evolutions of the cyclotron line energies in Her X-1, Vela X-1 and Cen X-3 as observed with Swift/BAT
• Relation of cyclotron resonant energy and luminosity in a strongly magnetized neutron star GRO J1008-57 observed by Insight-HXMT
• Discovery of the 5 keV cyclotron line followed by three harmonics in SwiftJ1626.6-5156
• New measurements of the cyclotron line energy in Cen X-3

Cited by in corpus (1)

• Revealing the state transition of Cen X-3 at high spectral resolution with Chandra