The evolution of the broadband temporal features observed in the black-hole transient MAXI J1820+070 with Insight-HXMT

Yanan Wang (1) , Long Ji , Mariano Méndez , J.L. Qu , Pierre Maggi (1) , M.Y. Ge , Erlin Qiao , L. Tao , S.N. Zhang , Diego Altamirano , L. Zhang , X. Ma , F.J. Lu , T.P. Li , Y. Huang , S.J. Zheng , Z. Chang , Y.L. Tuo , C. Gungor , L.M. Song , Y.P. Xu , X.L. Cao , Y.P. Chen , C.Z. Liu , Q.C. Bu , C. Cai , G. Chen , L. Chen , T.X. Chen , Y.B. Chen , W.W. Cui , J.K. Deng , Y.W. Dong , Y.Y. Du , M.X. Fu , G.H. Gao , H. Gao , M. Gao , Y.D. Gu , J. Guan , C.C. Guo , D.W. Han , J. Huo , S.M. Jia , L.H. Jiang , W.C. Jiang , J. Jin , Y.J. Jin , L.D. Kong , B. Li , C.K. Li , G. Li , M.S. Li , W. Li , X.B. Li , X.F. Li , Y.G. Li , Z.W. Li , X.H. Liang , J.Y. Liao , G.Q. Liu , H.W. Liu , X.J. Liu , Y.N. Liu , B. Lu , X.F. Lu , Q. Luo , T. Luo , B. Meng , Y. Nang , J.Y. Nie , G. Ou , N. Sai , R.C. Shang , X.Y. Song , L. Sun , Y. Tan , G.F. Wang , J. Wang , W.S. Wang , Y.D. Wang , Y.S. Wang , X.Y. Wen , B.B. Wu , B.Y. Wu , M. Wu , G.C. Xiao , S. Xiao , S.L. Xiong , J.W. Yang , S. Yang , Y.J. Yang , Q.B. Yi , Q.Q. Yin , Y. You , A.M. Zhang , C.M. Zhang , F. Zhang , H.M. Zhang , J. Zhang , T. Zhang , W.C. Zhang , W.Z. Zhang , Y.J. Zhang , Y.F. Zhang , Z.L. Zhang , H.S. Zhao , X.F. Zhao , D.K. Zhou , J.F. Zhou , R.L. Zhuang , Y.X. Zhu

1 ObAS - Observatoire astronomique de Strasbourg

We study the evolution of the temporal properties of MAXI J1820+070 during the 2018 outburst in its hard state from MJD 58,190 to 58,289 with Insight-HXMT in a broad energy band 1–150 keV. We find different behaviors of the hardness ratio, the fractional rms and time lag before and after MJD 58,257, suggesting a transition occurred around this point. The observed time lags between the soft photons in the 1–5 keV band and the hard photons in higher energy bands, up to 150 keV, are frequency-dependent: the time lags in the low-frequency range, 2–10 mHz, are both soft and hard lags with a timescale of dozens of seconds but without a clear trend along the outburst; the time lags in the high-frequency range, 1–10 Hz, are only hard lags with a timescale of tens of milliseconds; they first increase until around MJD 58,257 and decrease after this date. The high-frequency time lags are significantly correlated to the photon index derived from the fit to the quasi-simultaneous NICER spectrum in the 1–10 keV band. This result is qualitatively consistent with a model in which the high-frequency time lags are produced by Comptonization in a jet.

Domaines: Astrophysique [astro-ph]

Yanan Wang, Long Ji, Mariano Méndez, J.L. Qu, Pierre Maggi, et al.. The evolution of the broadband temporal features observed in the black-hole transient MAXI J1820+070 with Insight-HXMT. Astrophys.J., 2020, 896 (1), pp.33. ⟨10.3847/1538-4357/ab8db4⟩. ⟨hal-02572526⟩