New measurements of the cyclotron line energy in Cen X-3

We report results from the analysis of data from two observations of the accreting binary X-ray pulsar Cen X-3 carried out with the broad-band X-ray observatories Suzaku and NuSTAR. The pulse profile is dominated by a broad single peak and show some energy dependence with two additional weak pulse peaks at energies below 15 and 25 keV, respectively. The broad-band X-ray spectrum for 0.8-60.0 keV for Suzaku and 3.0-60.0 keV for NuSTAR is fitted well with high-energy cut-off power-law model along with soft-excess, multiple iron emission lines and a cyclotron absorption. The cyclotron line energy is found to be 30.29(-0.61)(+0.68) and 29.22(-0.27)(+0.28) keV, respectively, in the Suzaku and NuSTAR spectra. We make a comparison of these two measurements with four previous measurements of Cyclotron Resonant Scattering Feature (CRSF) in Cen X-3 obtained with Ginga, BeppoSAX, and RXTE. We find no evidence for a dependence of the CRSF on luminosity. Except for one CRSF measurement with BeppoSAX, the remaining measurements are consistent with a CRSF energy in the range of 29.5-30.0 keV over a luminosity range of 1.1-5.4 x 10(37) erg s(-1) different from several other sources that show considerable CRSF variation in the same luminosity range.

Automated summary

This study analyzed the observations of the accreting binary X-ray pulsar Cen X-3, revealing characteristics of the pulse profile and X-ray spectrum, as well as comparing the cyclotron line energy. The results showed consistency in the measurements across different luminosities, indicating no clear dependence of the Cyclotron Resonant Scattering Feature (CRSF) on the luminosity of the source.