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Ji, Long; Zhang, S. N.; Méndez, Mariano; Qu, J. L.; Maggi, Pierre; Zhang, S.; Altamirano, Diego; Zhang, L.; Ma, X.; Lu, F. J.; Li, T. P.; Huang, Y.; Zheng, S. J.; Chen, Y. P.; Chang, Z.; Tuo, Y. L.; Güngör, C.; Song, L. M.; Cao, X. L.; Chen, Y.; Liu, C. Z.; Bu, Q. C.; Cai, C.; Chen, G.; Chen, L.; Chen, T. X.; Chen, Y. B.; Cui, W. W.; Dong, Y. W.; Gao, H.; Gao, M.; Gu, Y. D.; Guan, J.; Guo, C. C.; Han, D. W.; Huo, J.; Jia, S. M.; Jiang, L. H.; Jiang, W. C.; Jin, Y. J.; Kong, L. D.; Li, B.; Li, G.; Li, M. S.; Li, W.; Li, X.; Li, X. B.; Li, X. F.; Li, Z. W.; Liang, X. H.; Liao, J. Y.; Liu, G. Q.; Liu, X. J.; Liu, Y. N.; Lu, B.; Lu, X. F.; Luo, Q.; Luo, T.; Meng, B.; Nang, Y.; Nie, J. Y.; Ou, G.; Sai, N.; Shang, R. C.; Song, X. Y.; Wang, G. F.; Wang, J.; Wang, W. S.; Wang, Y. D.; Wang, Y. S.; Wen, X. Y.; Wu, B. B.; Wu, B. Y.; Wu, M.; Xiao, G. C.; Xiong, S. L.; Yang, J. W.; Yang, Y. J.; Yi, Q. B.; You, Y.; Zhang, A. M.; Zhang, C. M.; Zhang, F.; Zhang, J.; Zhang, T.; Zhang, W. C.; Zhang, W.; Zhang, W. Z.; Zhang, Y.; Zhang, Y. F.; Zhang, Y.; Zhang, Z.; Zhang, Z. L.; Zhao, H. S.; Zhao, X. F.; Zhou, D. K.; Zhou, J. F.; Zhuang, R. L.; Zhu, Y.; Wang, Lingjun
The Astrophysical journal, 06/2020, Letnik: 896, Številka: 1Journal Article
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.
