The high-energy cyclotron line in 2S 1417-624 discovered with Insight-HXMT during the 2018 outburst

Date

2024-11-01

Author

Liu, Q.
Santangelo, A.
Kong, L. D.
Ducci, L.
Ji, L.
Wang, W.
Serim, Muhammed Miraç
GÜNGÖR, Can
Tuo, Y. L.
Serim, D.

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We report a detailed timing and spectral analysis of the X-ray pulsar 2S 1417-624 using the data from Insight-HXMT during the 2018 outburst. The pulse profiles are highly variable with respect to both unabsorbed flux and energy. A double-peaked pulse profile from the low flux evolved to a multi-peaked shape in the high-flux state. The pulse fraction is negatively correlated to the source flux in the range of similar to(1 - 6)x10(-9) erg cm(-2) s(-1), consistent with Rossi X-ray Timing Explorer (RXTE) studies during the 2009 giant outburst. The energy-resolved pulse profiles around the peak outburst showed a four-peak shape in the low-energy bands and gradually evolved to triple peaks at higher energies. The continuum spectrum is well described by typical phenomenological models, such as the cut-off power law and the power law with high-energy cut-off models. Notably, we discovered high-energy cyclotron resonant scattering features (CRSFs) for the first time, which are around 100 keV with a statistical significance of similar to 7 sigma near the peak luminosity of the outburst. This CRSF line is significantly detected with different continuum models and provides very robust evidence for its presence. Furthermore, pulse-phase-resolved spectroscopy confirmed the presence of the line, whose energy varied from 97 to 107 keV over the pulse phase and appeared to have a maximum value at the narrow peak phase of the profiles.

URI

https://hdl.handle.net/11511/118014

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Department of Physics, Article