Constant cyclotron line energy in Hercules X-1 -- Joint Insight-HXMT and   NuSTAR observations

G. C. Xiao (1,2); L. Ji (3); R. Staubert (3); M. Y. Ge (1); S. Zhang; (1,2); S. N. Zhang (1,2); A. Santangelo (3); L. Ducci (3); J. Y. Liao (1); C.; C. Guo (1,2); X. B. Li (1); W. Zhang (1,2); J. L. Qu (1,2); F. J. Lu (1); T.; P. Li (1,2,4); L. M. Song (1,2); Y. P. Xu (1); Q. C. Bu (1); C. Cai (1); X.; L. Cao (1); Z. Chang (1); G. Chen (1); L. Chen (5); T. X. Chen (1); Y. B.; Chen (4); Y. Chen (1); Y. P. Chen (1); W. Cui (1,4); W. W. Cui (1); J. K.; Deng (4); Y. W. Dong (1); Y. Y. Du (1); M. X. Fu (4); G. H. Gao (1,2); H. Gao; (1,2); M. Gao (1); Y. D. Gu (1); J. Guan (1); C. Gungor (1); C.C. Guo (1,2),; D. W. Han (1); Y. Huang (1); J. Huo (1); S. M. Jia (1); L. H. Jiang (1); W.; C. Jiang (1); J. Jin (1); L. D. Kong (1,2); B. Li (1); C. K. Li (1); G. Li; (1); M. S. Li (1); W. Li (1); X. Li (1); X. F. Li (1); Y. G. Li (1); Z. W. Li; (1); X. H. Liang (1); C. Z. Liu (1); G. Q. Liu (4); H. W. Liu (1); X. J. Liu; (1); Y. N. Liu (6); B. Lu (1); X. F. Lu (1); Q. Luo (1); T. Luo (1); X. Ma; (1); B. Meng (1); Y. Nang (1,2); J. Y. Nie (1); G. Ou (1); N. Sai (1,2); S.X.; Song (1); L. Sun (1); Y. Tan (1); L. Tao (1); Y. L. Tuo (1,2); C. Wang (2,7),; G. F. Wang (1); J. Wang (1); W. S. Wang (1); Y. S. Wang (1); X. Y. Wen (1),; B. B. Wu (1); B. Y. Wu (1,2); M. Wu (1); S. L. Xiong (1); J. W. Yang (1),; S.Yang (1); Y. J. Yang (1); Y. J. Yang (1); Q. B. Yin (1,2); Q. Q. Yin (1),; A. M. Zhang (1); C. M. Zhang (1); F. Zhang (1); H. M. Zhang (1); J. Zhang; (1); T. Zhang (1); W. Zhang (1,2); W. C. Zhang (1); W. Z. Zhang (5); Y. Zhang; (1); Y. Zhang (1,2); Y. F. Zhang (1); Y. J. Zhang (1); Z. Zhang (4); Z. Zhang; (5); Z. L. Zhang (1); H. S. Zhao (1); X. F. Zhao (1,2); S. J. Zheng (1); J.; F. Zhou (6); Y. Zhu (1); Y. X. Zhu (1) ((1) Key Laboratory of Particle; Astrophysics; Institute of High Energy Physics; Chinese Academy of Sciences,; Beijing; China; (2) University of Chinese Academy of Sciences; Chinese; Academy of Sciences; Beijing; China; (3) Institut f\"ur Astronomie und; Astrophysik; T\"ubingen; Germany; (4) Department of Physics; Tsinghua; University; Beijing; China; (5) Department of Astronomy; Beijing Normal; University; Beijing; China; (6) Department of Engineering Physics; Tsinghua; University; Beijing; China; (7) Key Laboratory of Space Astronomy and; Technology; National Astronomical Observatories; Chinese Academy of Sciences,; Beijing)

arXiv:1910.02393·astro-ph.HE·October 8, 2019

Constant cyclotron line energy in Hercules X-1 -- Joint Insight-HXMT and NuSTAR observations

G. C. Xiao (1,2), L. Ji (3), R. Staubert (3), M. Y. Ge (1), S. Zhang, (1,2), S. N. Zhang (1,2), A. Santangelo (3), L. Ducci (3), J. Y. Liao (1), C., C. Guo (1,2), X. B. Li (1), W. Zhang (1,2), J. L. Qu (1,2), F. J. Lu (1), T., P. Li (1,2,4), L. M. Song (1,2), Y. P. Xu (1)

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TL;DR

This study presents joint Insight-HXMT and NuSTAR observations of Her X-1, revealing that the cyclotron line energy remains constant around 37.5 keV after previously observed decay, providing new insights into its long-term behavior.

Contribution

The paper provides the first joint analysis confirming the constant cyclotron line energy in Her X-1 after a long decay phase, resolving a long-standing mystery.

Findings

01

The line energy remains stable at ~37.5 keV after flux correction.

02

Joint observations show consistent timing and spectral properties.

03

The long decay phase of the CRSF energy has ended.

Abstract

The long-term evolution of the centroid energy of the CRSF in Her X-1 is still a mystery. We report a new measurement from a campaign between {\sl Insight}-HXMT and {\sl NuSTAR} performed in February 2018. Generally, the two satellites show well consistent results of timing and spectral properties. The joint spectral analysis confirms that the previously observed long decay phase has ended, and that the line energy instead keeps constant around 37.5 keV after flux correction.

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Taxonomy

TopicsSolar and Space Plasma Dynamics · Ionosphere and magnetosphere dynamics · Gamma-ray bursts and supernovae