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1. Physical origin of the non-physical spin evolution of MAXI J1820 + 070

Author

Cunguo Wang, Shaolin Xiong, B. S. Liu, B. B. Wu, H. Gao, J. Y. Liao, H. M. Zhang, R. C. Ma, Y. S. Wang, Y. F. Zhang, Xue-Feng Lu, C. Cai, Lian Tao, Shuinai Zhang, Tong Li, G. H. Gao, S. M. Jia, Tao Luo, M. Wu, X. Y. Song, Bo Li, Wenxiong Li, J. Jin, Xin-Fu Zhao, He-Yang Liu, S. Xiao, Lei Sun, Junqiang Zhang, J. L. Qu, Y. H. Tan, C. K. Li, Y. Nang, Peng Zhang, R. J. Yang, H. W. Liu, N. Sai, Yuan-Yuan Du, Y. G. Zheng, X. X. Li, Z. Chang, Y. B. Chen, Qiu-Yi Luo, Tian-Xiang Chen, Z. W. Li, F. J. Lu, Qingcui Bu, L. M. Song, S. J. Zheng, XiangYang Wen, X. H. Ma, Da-Wei Han, Ya Fang Huang, H. S. Zhao, Yuan You, Qi-Bin Yi, D. K. Zhou, P. J. Wang, W. S. Wang, Ge Ou, Yi Zhang, C. Z. Liu, Sisi Yang, J. Y. Nie, Xin Ren, Liang Zhang, Cheng-Cheng Guo, Ming-Yu Ge, L. Chen, Wan-Chang Zhang, Xiong Li, Yu-Dong Gu, X. J. Liu, Libin Wang, X. L. Cao, Q. Q. Yin, Y. P. Chen, Y. Wang, X. H. Liang, Fuqin Zhang, S. N. Zhang, Y. P. Xu, B. Y. Wu, Xuelong Li, J. Guan, L. D. Kong, Wei Cui, W. C. Zhang, Jia Huo, Gang Li, Wenhan Jiang, Bin Meng, Y. J. Yang, and G. C. Xiao

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Hardness ratio, Astrophysics::High Energy Astrophysical Phenomena, Spin transition, FOS: Physical sciences, Binary number, Astronomy and Astrophysics, Astrophysics, Black hole, Innermost stable circular orbit, Accretion disc, Space and Planetary Science, Coincident, Spectral analysis, 83C57, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics
Abstract

We report on the Insight-HXMT observations of the new black hole X-ray binary MAXI J1820+070 during its 2018 outburst. Detailed spectral analysis via the continuum fitting method shows an evolution of the inferred spin during its high soft sate. Moreover, the hardness ratio, the non-thermal luminosity and the reflection fraction also undergo an evolution, exactly coincident to the period when the inferred spin transition takes place. The unphysical evolution of the spin is attributed to the evolution of the inner disc, which is caused by the collapse of a hot corona due to condensation mechanism or may be related to the deceleration of a jet-like corona. The studies of the inner disc radius and the relation between the disc luminosity and the inner disc radius suggest that, only at a particular epoch, did the inner edge of the disc reach the innermost stable circular orbit and the spin measurement is reliable. We then constrain the spin of MAXI J1820+070 to be a*=0.2^{+0.2}_{-0.3}. Such a slowly spinning black hole possessing a strong jet suggests that its jet activity is driven mainly by the accretion disc rather than by the black hole spin., Comment: 14 pages, 13 figures, 5 tables, accepted for publication in MNRAS

Published
2021
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2. HXMT identification of a non-thermal X-ray burst from SGR J1935+2154 and with FRB 200428

Author

Y. J. Jin, Z. Chang, J. Y. Liao, H. M. Zhang, Y. F. Zhang, X. B. Li, Y. G. Li, Chun-sheng Zhang, Wenhan Jiang, Bo Li, Yu-Xuan Zhu, G. H. Gao, J. Jin, M. Wu, Y. Zhang, Xin-Fu Zhao, Zhi Zhang, Y. H. Tan, Y. X. Zhu, R. C. Shang, C. Cai, B. Lu, Fuqin Zhang, J. K. Deng, S. N. Zhang, W. C. Xue, X. X. Li, Y. G. Zheng, J. F. Zhou, Ming-Yu Ge, X. H. Ma, Wenxiong Li, Tian-Xiang Chen, F. J. Lu, Y. S. Wang, D. K. Zhou, Wei Cui, T. Zhang, Aimei Zhang, Lin Lin, Li-Ming Song, B. S. Liu, Lei Sun, C. Z. Liu, S. J. Zheng, Luhua Jiang, Y. P. Xu, B. B. Wu, X. L. Cao, Tao Luo, XiangYang Wen, Xue-Feng Lu, Bin Meng, S. Xiao, Y. B. Chen, Junqiang Zhang, Tong Li, H. W. Liu, N. Sai, Mao-Shun Li, Yunchao Liu, Sisi Yang, Y. J. Yang, S. M. Jia, Yuan You, L. D. Kong, Songbo Zhang, Cunguo Wang, Qi-Bin Yi, Yu-Dong Gu, Q. Q. Yin, Y. P. Chen, Xuelong Li, J. Guan, X. J. Liu, W. Z. Zhang, Yuan-Yuan Du, Gang Chen, X. H. Liang, G. C. Xiao, R. L. Zhuang, GuoQing Liu, Jia Huo, Y. Nang, Gang Li, Shaolin Xiong, Y. J. Zhang, H. Gao, Qiu-Yi Luo, Z. Zhang, Y. L. Tuo, J. W. Yang, Bing Zhang, B. Y. Wu, Lian Tao, X. Y. Song, H. S. Zhao, G. F. Wang, W. S. Wang, Ge Ou, W. C. Zhang, J. Y. Nie, Yi-Qiao Dong, Cheng-Cheng Guo, C. K. Li, H. Xu, Z. W. Li, Da-Wei Han, Z. L. Zhang, M. X. Fu, Yue Zhang, Ya Fang Huang, J. Z. Wang, L. Chen, Wan-Chang Zhang, Weiguang Cui, Qingcui Bu, Min Gao, and J. L. Qu

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010504 meteorology & atmospheric sciences, X-ray, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Magnetar, 01 natural sciences, Coincidence, Radio spectrum, 0103 physical sciences, Thermal, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Event (particle physics), 0105 earth and related environmental sciences, Delay time
Abstract

Fast radio bursts (FRBs) are short pulses observed in radio band from cosmological distances. One class of models invoke soft gamma-ray repeaters (SGRs), or magnetars, as the sources of FRBs. Some radio pulses have been observed from some magnetars, however, no FRB-like events had been detected in association any magnetar burst, including one giant flare. Recently, a pair of FRB-like bursts (FRB 200428 hereafter) separated by milliseconds (ms) were detected from the general direction of the Galactic magnetar SGR J1935+2154. Here we report the detection of a non-thermal X-ray burst in the 1-250 keV energy band with the Insight-HXMT satellite, which we identify as emitted from SGR J1935+2154. The burst showed two hard peaks with a separation of 34 ms, broadly consistent with that of the two bursts in FRB 200428. The delay time between the double radio and X-ray peaks is about 8.57 s, fully consistent with the dispersion delay of FRB 200428. We thus identify the non-thermal X-ray burst is associated with FRB 200428 whose high energy counterpart is the two hard peaks in X-ray. Our results suggest that the non-thermal X-ray burst and FRB 200428 share the same physical origin in an explosive event from SGR J1935+2154., 24 pages, 9 figures, 6 tables; initial submission to a journal on May 9th, 2020. Significant changes include updated localization and detailed spectral evolution of the X-ray burst, and better determination of the two narrow X-ray peaks corresponding to the two radio pulses. Conclusions are strengthened. Nature Astronomy online on Feb. 18, 2021

Published
2021
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3. Insight-HXMT observations of jet-like corona in a black hole X-ray binary MAXI J1820+070

Author

Xiaobo Li, Zhu Liu, Y. L. Tuo, J. W. Yang, Shuang-Nan Zhang, Aimei Zhang, Yong Chen, Wei Wang, Li Chen, Mao-Shun Li, Hai-Sheng Zhao, C. K. Li, Cheng-Kui Li, Weimin Yuan, Yanji Yang, Juan Wang, Yu-Xuan Zhu, Ju Guan, Xiao-Fan Zhao, Bozena Czerny, Ling-Jun Wang, Qingwen Wu, Xufang Li, Gang Li, R. C. Shang, B. B. Wu, Shaolin Xiong, Yifei Zhang, Tong Zhang, X. Y. Song, Yongjie Zhang, N. Sai, Erlin Qiao, Yi Zhang, Ti-Pei Li, Lian Tao, Wei-Wei Cui, Wan-Chang Zhang, Bin Meng, Yue Zhu, Y. Nang, Liang Sun, Yu-Peng Chen, Ming-Yu Ge, Xiao-Jing Liu, Wei Cui, Zi-Gao Dai, Bobing Wu, Shu Zhang, Gang Chen, Bing Li, Yuan-Yuan Du, Zhi Chang, G. F. Wang, Xiang Ma, Ying Tan, L. D. Kong, T. Luo, Fangjun Lu, Guan-Hua Gao, Shuo Xiao, Juan Zhang, D. K. Zhou, Shu-Mei Jia, Y. P. Chen, Chichuan Jin, Bifang Liu, Wei Li, Jian-Feng Zhou, Ge Ou, Yupeng Xu, Bo Lu, Bei You, He Gao, Chen Wang, Fan Zhang, Yanguo Li, Chong Luo, Qi Luo, Jing Jin, Jing-Kang Deng, Li-Ming Song, Cheng-Cheng Guo, XiangYang Wen, Xiaohua Liang, C. X. Liu, C. Cai, Yue Huang, Yuan You, Jia Huo, Zi-Liang Zhang, J. C. Liu, Zhao Zhang, Yongwei Dong, Qi-Bin Yi, Mei Wu, W. C. Jiang, Jin-Yuan Liao, X. L. Cao, Xue-Feng Lu, Guang-Cheng Xiao, Wei Zhang, Chengmo Zhang, Yu-Dong Gu, Hong-Mei Zhang, Tian-Xiang Chen, GuoQing Liu, Y. N. Liu, Qian-Qing Yin, Zheng-Wei Li, Xian Li, Hongwei Liu, Sheng Yang, Wenshuai Wang, Luhua Jiang, Jin-Lu Qu, Jianyin Nie, Min-Xue Fu, Yu-Sa Wang, YongJie Jin, Yue Zhang, Qingcui Bu, Wen-Zhao Zhang, Da-Wei Han, M. Gao, and Shi-Jie Zheng

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Science, Phase (waves), X-ray binary, FOS: Physical sciences, General Physics and Astronomy, Astrophysics, Radiation, 01 natural sciences, Article, General Biochemistry, Genetics and Molecular Biology, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Jet (fluid), Multidisciplinary, Shock (fluid dynamics), 010308 nuclear & particles physics, General Chemistry, Corona, Astrophysics - Astrophysics of Galaxies, High-energy astrophysics, Black hole, Astrophysics of Galaxies (astro-ph.GA), Physics::Space Physics, Reflection (physics), Compact astrophysical objects, Astrophysics - High Energy Astrophysical Phenomena
Abstract

A black hole X-ray binary produces hard X-ray radiation from its corona and disk when the accreting matter heats up. During an outburst, the disk and corona co-evolves with each other. However, such an evolution is still unclear in both its geometry and dynamics. Here we report the unusual decrease of the reflection fraction in MAXI J1820+070, which is the ratio of the coronal intensity illuminating the disk to the coronal intensity reaching the observer, as the corona is observed to contrast during the decay phase. We postulate a jet-like corona model, in which the corona can be understood as a standing shock where the material flowing through. In this dynamical scenario, the decrease of the reflection fraction is a signature of the corona's bulk velocity. Our findings suggest that as the corona is observed to get closer to the black hole, the coronal material might be outflowing faster., 11 pages, 5 figures; published in Nature Communications; An artist's impression of Figure 5 is updated here, and the animation is available at http://youbei.work/research/

Published
2021

4. Confirming the spin parameter of the black hole in Cygnus X-1 using the Insight-HXMT

Author

Yongjie Zhang, Xian Li, Sheng Yang, Zi-Liang Zhang, Yan-Ting Dong, Lian Tao, X. Y. Song, Yupeng Xu, YongJie Jin, Ji-Ren Liu, Mei Wu, T. Luo, Jing Jin, Wan-Chang Zhang, GuoQing Liu, Chen Wang, Wei Cui, S. Xiao, XiangYang Wen, Yu-Dong Gu, Jianyin Nie, Jing-Kang Deng, Xiao-Fan Zhao, J. W. Yang, Yanji Yang, Xiaobo Li, Jia Huo, Yuan You, Gang Li, Youli Tuo, Mao-Shun Li, Qi-Bin Yi, Xufang Li, B. S. Liu, Zheng-Wei Li, Jin-Lu Qu, Yanguo Li, Xue-Ying Zheng, Yu-Peng Chen, Wei Zhang, Cheng-Cheng Guo, Yi Zhang, Li-Ming Song, Juan Zhang, N. Sai, C. Cai, Shaolin Xiong, Xue-Feng Lu, ShiJie Zheng, Jian-Feng Zhou, Q. Luo, Y. P. Chen, L. D. Kong, Wei-Wei Cui, Yongwei Dong, Yuan-Yuan Du, Bing Li, Da-Wei Han, Bin Meng, HongMei Zhang, Li-Jun Gou, Ying Tan, Zhi Zhang, C. L. Zhang, Juan Wang, D. K. Zhou, Shu Zhang, Min-Xue Fu, Jin-Yuan Liao, X. L. Cao, H. T. Liu, LuHua Jiang, Hai-Sheng Zhao, Yu-Sa Wang, X. H. Liang, Ye Feng, Yue Zhang, Guang-Cheng Xiao, Bo Lu, Qingcui Bu, Fangjun Lu, He Gao, Li Chen, Ju Guan, Yong Chen, B. B. Wu, Tong Zhang, Guan-Hua Gao, Shu-Mei Jia, W. S. Wang, Ge Ou, W. C. Jiang, Liang Sun, Tian-Xiang Chen, Qian-Qing Yin, Wei Li, Y. Nang, G. F. Wang, Xiang Ma, Yue-Zhu, Zhao Zhang, W. Z. Zhang, Nan Jia, Fan Zhang, Yu-Xuan Zhu, Yifei Zhang, Shuang-Nan Zhang, Aimei Zhang, Ming-Yu Ge, Xiao-Jing Liu, Yu-Feng Li, Yue Huang, R. C. Shang, Zhi Chang, Zhen-Xuan Liao, H. W. Liu, Gang Chen, Cheng-Kui Li, Yi-Rong Yang, Y. N. Liu, Bobing Wu, Ti-Pei Li, M. Gao, Xue-Shan Zhao, R. L. Zhuang, and C. X. Liu

Subjects
Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Spectral line, Orbital inclination, law.invention, Telescope, Rotating black hole, Space and Planetary Science, Fitting methods, law, 0103 physical sciences, System parameters, 010303 astronomy & astrophysics, Spin-½, Dimensionless quantity
Abstract

Recently, the system parameters of Cygnus X-1, i.e., the black hole mass M, the orbital inclination i and the source distance D, have been updated. As the input constraints of the continuum-fitting method, it is necessary to refine the spin with these new parameters. The Hard X-ray Modulation Telescope (HXMT, also named Insight) was successfully launched on June 15th, 2017 in China. In this work, we analyzed spectra obtained by the Insight-HXMT during 2017-2018 and re-estimated the spin via the continuum-fitting method. We first re-estimated the spin using old parameters and found the dimensionless spin parameter to be a ⁎ > 0.934 (3σ), which is consistent with previous measurements both from the continuum-fitting and iron-line fitting methods ( Gou et al. 2011 , Gou et al. 2014 ; Fabian et al. 2012 , Walton et al. 2016 , Tomsick et al. 2018 ). Then, when the new parameters were applied, we obtained an increased spin: a ⁎ > 0.967 (3σ), which is also consistent with the recent measurement (Zhao et al. 2020, submitted to ApJ) and also confirms an extreme Kerr black hole lying in this system.

Published
2020
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5. Insight-HXMT study of the timing properties of Sco X-1

Author

J. Z. Wang, J. Y. Nie, Y. J. Yang, Xiaobo Li, Weiguang Cui, J. Guan, Qingcui Bu, L. M. Song, Yu-Dong Gu, G. C. Xiao, Luhua Jiang, J. Jin, D. K. Zhou, Y. X. Zhu, X. H. Liang, W. C. Zhang, B. Lu, GuoQing Liu, Ming-Yu Ge, Chun-sheng Zhang, Yi-Qiao Dong, Min Gao, B. B. Wu, Wenhan Jiang, Jia Huo, Y. H. Tan, Cheng-Cheng Guo, J. L. Qu, Gang Li, Y. B. Chen, F. J. Lu, Xin-Fu Zhao, R. C. Shang, J. F. Zhou, Bing Li, XiangYang Wen, Lian Tao, Y. S. Wang, Gang Chen, Wei Cui, B. Y. Wu, Tian-Xiang Chen, T. Zhang, X. Y. Song, X. J. Liu, Tao Luo, Da-Wei Han, Bin Meng, L. Chen, Mao-Shun Li, S. Xiao, Xue-Feng Lu, Tong Li, S. M. Jia, Fuqin Zhang, Z. Zhang, S. N. Zhang, Z. Chang, Yunchao Liu, R. L. Zhuang, Junqiang Zhang, Wan-Chang Zhang, W. S. Wang, Y. Nang, Ge Ou, Yuan-Yuan Du, W. Z. Zhang, Lei Sun, Y. J. Jin, C. Z. Liu, J. K. Deng, L. D. Kong, H. W. Liu, N. Sai, Shaolin Xiong, Cunguo Wang, Y. J. Zhang, X. H. Ma, H. Gao, Sisi Yang, Yupeng Xu, Qiu-Yi Luo, X. F. Li, H. S. Zhao, G. F. Wang, Y. L. Tuo, C. Cai, Wenxiong Li, J. W. Yang, Yu-Xuan Zhu, X. L. Cao, X. X. Li, S. J. Zheng, Yuan You, G. H. Gao, Qi-Bin Yi, M. Wu, Q. Q. Yin, Y. P. Chen, Y. Zhang, Y. G. Li, Aimei Zhang, J. Y. Liao, H. M. Zhang, Y. F. Zhang, Ya Fang Huang, Z. L. Zhang, C. K. Li, Z. W. Li, and M. X. Fu

Subjects
Physics, High energy, 010308 nuclear & particles physics, Phase (waves), Astronomy and Astrophysics, Astrophysics, Horizontal branch, 01 natural sciences, law.invention, Telescope, Root mean square, Space and Planetary Science, law, 0103 physical sciences, Modulation (music), 010303 astronomy & astrophysics, Energy (signal processing), Flare
Abstract

We present a detailed timing study of the brightest persistent X-ray source Sco X-1 using the data collected by the Hard X-ray Modulation Telescope ( I n s i g h t -HXMT) from July 2017 to August 2018. A complete Z-track hardness-intensity diagram (HID) is obtained. The normal branch oscillations (NBOs) at ∼ 6 Hz in the lower part of the normal branch (NB) and the flare branch oscillations (FBOs) at ∼ 16 Hz in the beginning part of the flaring branch (FB) are found in observations with the Low Energy X-ray Telescope (LE) and the Medium Energy X-ray Telescope (ME) of I n s i g h t -HXMT, while the horizontal branch oscillations (HBOs) at ∼ 40 Hz and the kilohertz quasi-periodic oscillations (kHz QPOs) at ∼ 800 Hz are found simultaneously above 20 keV for the first time on the horizontal branch (HB) by the High Energy X-ray Telescope (HE) and ME. We find that for all types of the observed QPOs, the centroid frequencies are independent of energy, while the root mean square (rms) increases with energy; the centroid frequencies of both the HBOs and kHz QPOs increase along the Z-track from the top to the bottom of the HB; and the NBOs show soft phase lags increasing with energy. A continuous QPO transition from the FB to NB in ∼ 200 s are also detected. Our results indicate that the non-thermal emission is the origin of all types of QPOs, the innermost region of the accretion disk is non-thermal in nature, and the corona is nonhomogeneous geometrically.

Published
2020
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6. A Variable Ionized Disk Wind in the Black Hole Candidate EXO 1846–031

Author

Junjie Mao, H. M. Zhang, Junqiang Zhang, ShiJie Zheng, C. K. Li, Thomas Dauser, Yuan-Yuan Du, C. Cai, R. C. Shang, Bing Li, Ming-Yu Ge, Xiao-Jing Liu, Y. J. Yang, Xufang Li, Gang Li, Shu-Mei Jia, Mariano Mendez, Ge Ou, Y. Nang, L. D. Kong, Yi Zhang, P. Maggi, N. Sai, Yin Xu, Long Ji, Yanan Wang, Bin Meng, Han Zhao, S. Yang, Q. B. Yi, B. Y. Wu, Lei Sun, Y. Huang, W. G. Li, Shaolin Xiong, Fangjun Lu, Li-Ming Song, C. Z. Liu, Jing Jin, Bobing Wu, Mingyu Wu, Xiaohua Liang, Javier A. García, X. F. Li, Yuan You, Y. S. Wang, Ti-Pei Li, Tianran Chen, Youli Tuo, Xiong Li, Yu-Dong Gu, Jin-Lu Qu, Y. Tan, W. C. Jiang, Zhe Chang, F. Zhang, X.W. Ma, Yuan Wang, Lian Tao, Diego Altamirano, L. Chen, X. Y. Song, D. K. Zhou, Wan-Chang Zhang, Jia Huo, X. Y. Wen, Z. W. Li, Xin Lu, G. C. Xiao, Jundan Nie, Hongwei Liu, Shuang-Nan Zhang, S. N. Zhang, Q. Q. Yin, Y. P. Chen, T. Luo, Liang Zhang, Wei Zhang, Cheng-Cheng Guo, W. S. Wang, Jin-Yuan Liao, X. L. Cao, G. H. Gao, Shuo Xiao, Xuchao Zhao, Ju Guan, Weiguang Cui, Qingcui Bu, Da-Wei Han, Q. Luo, Y. B. Chen, Observatoire astronomique de Strasbourg (ObAS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Astronomy

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010504 meteorology & atmospheric sciences, High-energy astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Accretion (astrophysics), Spectral line, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Ionization, 0103 physical sciences, Reflection (physics), Intermediate state, Emission spectrum, Spectral resolution, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, QC, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

After 34 years, the black-hole candidate EXO 1846-031 went into outburst again in 2019. We investigate its spectral properties in the hard intermediate and the soft states with NuSTAR and Insight-HXMT. A reflection component has been detected in the two spectral states but possibly originating from different illumination spectra: in the intermediate state, the illuminating source is attributed to a hard coronal component, which has been commonly observed in other X-ray binaries, whereas in the soft state the reflection is probably produced by the disk self-irradiation. Both cases support EXO 1846-031 as a low inclination system of ~40 degrees. An absorption line is clearly detected at ~7.2 keV in the hard intermediate state, corresponding to a highly ionized disk wind (log {\xi} > 6.1) with a velocity up to 0.06c. Meanwhile, quasi-simultaneous radio emissions have been detected before and after the X-rays, implying the co-existence of disk winds and jets in this system. Additionally, the observed wind in this source is potentially driven by magnetic forces. The absorption line disappeared in the soft state and a narrow emission line appeared at ~6.7 keV on top of the reflection component, which may be evidence for disk winds, but data with the higher spectral resolution are required to examine this., Comment: Accepted for publication in ApJ

Published
2021
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7. Timing analysis of the black hole candidate EXO 1846-031 with Insight-HXMT monitoring

Author

Ju Guan, Yuan-Hang Zhang, Wei Zhang, Yue Zhang, W. C. Jiang, Y. G. Zheng, Cheng-Cheng Guo, Cheng-Kui Li, R. C. Shang, W. S. Wang, Shaolin Xiong, GuoQing Liu, Yongwei Dong, Tian-Xiang Chen, Yupeng Xu, Jian-Feng Zhou, Yu-Dong Gu, Qian-Qing Yin, Wei Li, Jianyin Nie, Wei Cui, X. L. Cao, Qingcui Bu, Yongjie Zhang, J. W. Yang, Jing-Yuan Liao, XiangYang Wen, Xiang Ma, Bing Li, Wen-Zhao Zhang, B. B. Wu, Tong Zhang, Zhao Zhang, Lian Tao, X. Y. Song, Zheng-Wei Li, Jing Jin, Zhi Chang, Mao-Shun Li, Yue Zhu, Jia Huo, Wei-Wei Cui, Xian Li, Hongwei Liu, Y. G. Li, Sheng Yang, Bo Lu, ShiJie Zheng, Jin-Lu Qu, H. W. Liu, Da-Wei Han, Wan-Chang Zhang, C. Cai, HongMei Zhang, Gang Li, Luhua Jiang, Yuan-Yuan Du, Min-Xue Fu, Yue Huang, He Xu, Juan Zhang, Xiaobo Li, Min Gao, Shuang-Nan Zhang, Zhi Zhang, Yu-Sa Wang, Li-Ming Song, Xufang Li, Liang Sun, Aimei Zhang, Tao Luo, Yu-Peng Chen, S. Xiao, Fangjun Lu, Li Chen, Shu Zhang, Guan-Hua Gao, Xiao-Fan Zhao, Ling-Jun Wang, N. Sai, He Gao, Q. Luo, Yifei Zhang, Bin Meng, Fan Zhang, Y. P. Chen, Mei Wu, Yu-Xuan Zhu, B. S. Liu, D. K. Zhou, Shu-Mei Jia, Ming-Yu Ge, Xiao-Jing Liu, Juan Wang, Xue-Feng Lu, Ge Ou, Chengmo Zhang, R. L. Zhuang, Hai-Sheng Zhao, C. X. Liu, Gang Chen, Yong Chen, Y. N. Liu, Y. Nang, Guang-Cheng Xiao, G. F. Wang, Jing-Kang Deng, Xiaohua Liang, Yuan You, Youli Tuo, Qi-Bin Yi, Bobing Wu, Ti-Pei Li, Y. J. Yang, Ying Tan, Zi-Liang Zhang, YongJie Jin, Yanji Yang, Yi Zhang, L. D. Kong, and Chen Wang

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, Static timing analysis, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846–031 during its outburst in 2019 with the observations of Insight-HXMT, NICER and MAXI. This outburst can be classified roughly into four different states. Type-C quasi-periodic oscillations (QPOs) observed by NICER (about 0.1–6 Hz) and Insight-HXMT (about 0.7–8 Hz) are also reported in this work. Meanwhile, we study various physical quantities related to QPO frequency. The QPO rms–frequency relationship in the energy band 1–10 keV indicates that there is a turning pointing in frequency around 2 Hz, which is similar to that of GRS 1915+105. A possible hypothesis for the relationship above may be related to the inclination of the source, which may require a high inclination to explain it. The relationships between QPO frequency and QPO rms, hardness, total fractional rms and count rate have also been found in other transient sources, which can indicate that the origin of type–C QPOs is non-thermal.

Published
2020

8. Discovery of oscillations above 200 keV in a black hole X-ray binary with Insight-HXMT

Author

Yu-Dong Gu, Yue Zhu, L. D. Kong, T. Luo, Chen Wang, Yanji Yang, Shaolin Xiong, Liang Zhang, Yi Zhang, Y. J. Yang, Zi-Liang Zhang, XiangYang Wen, Jia Huo, Hai-Sheng Zhao, Jing-Kang Deng, YongJie Jin, Jin-Yuan Liao, X. L. Cao, Fu-Guo Xie, Ju Guan, X. Y. Song, Mao-Shun Li, D. K. Zhou, Min-Xue Fu, Yu-Peng Chen, Xian Li, Y. P. Chen, Xiaohua Liang, Zheng-Wei Li, Yuan You, Hongwei Liu, Sheng Yang, Qi-Bin Yi, Luhua Jiang, Yanguo Li, Yuan-Yuan Du, Wei-Wei Cui, He Xu, Yu-Sa Wang, Yongjie Zhang, Li-Ming Song, Wan-Chang Zhang, Cheng-Cheng Guo, Wenshuai Wang, Li Chen, Zhi Zhang, Lian Tao, Y. Nang, Shu Zhang, Yongwei Dong, W. C. Jiang, Xue-Feng Lu, Xiao-Fan Zhao, Yue Zhang, Jianyin Nie, Shuo Xiao, Bo Lu, M. Gao, Xiaobo Li, G. F. Wang, Xiang Ma, Chengmo Zhang, Mei Wu, Guan-Hua Gao, Ying Tan, Shi-Jie Zheng, Tian-Xiang Chen, Qingcui Bu, Shu-Mei Jia, Qian-Qing Yin, Wen-Zhao Zhang, Ge Ou, Liang Sun, Bing Li, Jin-Lu Qu, B. B. Wu, Tong Zhang, Y. L. Tuo, Da-Wei Han, J. W. Yang, Juan Zhang, Long Ji, Feng Yuan, Jian-Feng Zhou, Guang-Cheng Xiao, R. L. Zhuang, Yupeng Xu, C. X. Liu, Wei Cui, Fangjun Lu, Jing Jin, Bobing Wu, He Gao, Zhi Chang, Juan Wang, Yifei Zhang, Ti-Pei Li, GuoQing Liu, Ming-Yu Ge, Xiao-Jing Liu, Fan Zhang, Qi Luo, Yong Chen, Yue Huang, Yu-Xuan Zhu, Shuang-Nan Zhang, Aimei Zhang, Cheng-Kui Li, Xufang Li, Gang Li, Wei Li, C. Cai, Zhao Zhang, N. Sai, Bin Meng, R. C. Shang, Gang Chen, Wei Zhang, Bai-Sheng Liu, Ling-Jun Wang, Hong-Mei Zhang, and Y. N. Liu

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Jet (fluid), Photon, Accretion (meteorology), Astrophysics::High Energy Astrophysical Phenomena, X-ray binary, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, law.invention, Black hole, Telescope, law, Quasiperiodic function, Precession, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Low-frequency quasi-periodic oscillations (LFQPOs) are commonly found in black hole X-ray binaries, and their origin is still under debate. The properties of LFQPOs at high energies (above 30 keV) are closely related to the nature of the accretion flow in the innermost regions, and thus play a crucial role in critically testing various theoretical models. The Hard X-ray Modulation Telescope (Insight-HXMT) is capable of detecting emissions above 30 keV, and is therefore an ideal instrument to do so. Here we report the discovery of LFQPOs above 200 keV in the new black hole MAXI J1820+070 in the X-ray hard state, which allows us to understand the behaviours of LFQPOs at hundreds of kiloelectronvolts. The phase lag of the LFQPO is constant around zero below 30 keV, and becomes a soft lag (that is, the high-energy photons arrive first) above 30 keV. The soft lag gradually increases with energy and reaches ~0.9s in the 150-200 keV band. The detection at energies above 200 keV, the large soft lag and the energy-related behaviors of the LFQPO pose a great challenge for most currently existing models, but suggest that the LFQPO probably originates from the precession of a small-scale jet., 36 pages, 12 figures, 3 tables; published in Nature Astronomy

Published
2020

9. Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite

Author

Mao-Shun Li, YongJie Jin, Cheng-Kui Li, Xiaobo Li, ChunLei Zhang, Shaolin Xiong, C. L. Zou, ShiJie Zheng, C. Wang, W. C. Jiang, Min-Xue Fu, Yifei Zhang, Min Gao, Yu-Sa Wang, Tian-Xiang Chen, Wei Chen, Yuan-Yuan Du, Xufang Li, Jin-Lu Qu, Guan-Hua Gao, Yue Zhu, Shu-Mei Jia, Wei Li, J. W. Yang, Yue Zhang, Tong Zhang, N. Sai, Ming-Yu Ge, Xiao-Jing Liu, Tao Luo, WenHui Tao, Ge Ou, Wen-Zhao Zhang, Qiang Zhang, Juan Wang, Bing Li, Bin Yuan, Guang-Cheng Xiao, ShenYi Zhang, Zhao Zhang, Qi Luo, Bin Meng, Xiao-Fan Zhao, R. C. Shang, Liang Zhang, Bobing Wu, X. Y. Song, Yupeng Xu, Jianling Zhao, Da-Wei Han, Hai-Sheng Zhao, Wei Zhang, Yue Huang, Ti-Pei Li, Can Güngör, HongMei Zhang, Jing Jin, Cheng-Cheng Guo, C. Cai, Jianyin Nie, Wan-Chang Zhang, GuoHong Shen, XiangYang Wen, Shuo Xiao, Yongwei Dong, Yong Chen, Yanguo Li, R. L. Zhuang, C. X. Liu, Li-Ming Song, Wei Hu, Yan Huang, Jin-Yuan Liao, X. L. Cao, Bo Lu, Y. Nang, Yu-Peng Chen, Jing-Kang Deng, Xue-Feng Lu, JiaXi Yu, Xiaohua Liang, Wei-Wei Cui, Qingcui Bu, Shu Zhang, Huanyu Wang, Gang Chen, Chengmo Zhang, Ju Guan, G. F. Wang, Xiang Ma, Zhi Zhang, Youli Tuo, Qi-Bin Yi, Y. P. Chen, Y. N. Liu, Zhi Chang, He Xu, Li Chen, ZiJian Li, Ying Tan, L. Sun, Bai-Sheng Liu, Fangjun Lu, He Gao, Mei Wu, Fan Zhang, Jia Huo, Gang Li, Xian Li, Hongwei Liu, Sheng Yang, Yu-Xuan Zhu, Luhua Jiang, Yongjie Zhang, Lian Tao, Wei Cui, Juan Zhang, Shuang-Nan Zhang, Aimei Zhang, GuoQing Liu, Yu-Dong Gu, Zheng-Wei Li, Wenshuai Wang, ShaoZhen Liu, L. D. Kong, LinLi Yan, Yanji Yang, Yi Zhang, Yuan Liu, and Zi-Liang Zhang

Subjects
Astrophysics::High Energy Astrophysical Phenomena, media_common.quotation_subject, FOS: Physical sciences, General Physics and Astronomy, 01 natural sciences, law.invention, Telescope, law, 0103 physical sciences, Calibration, Demodulation, Ground segment, 010306 general physics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Remote sensing, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Payload, Astrophysics::Instrumentation and Methods for Astrophysics, Sky, Satellite, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Gamma-ray burst
Abstract

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results., 29 pages, 40 figures, 6 tables, to appear in Sci. China-Phys. Mech. Astron. arXiv admin note: text overlap with arXiv:1910.04434

Published
2020
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10. Switches between accretion structures during flares in 4U 1901+03

Author

Z. Chang, Fuqin Zhang, S. N. Zhang, Qiu-Yi Luo, Y. B. Chen, B. B. Wu, Tao Luo, Aimei Zhang, J. Y. Zhang, Ming-Yu Ge, Armin Nabizadeh, Y. G. Li, S. Xiao, Y. L. Tuo, J. W. Yang, L. Chen, Chun-sheng Zhang, Peng Zhang, Yu-Dong Gu, Sergey S. Tsygankov, C. K. Li, Y. J. Jin, J. Y. Nie, M. X. Fu, Yue Zhang, X. J. Liu, Luhua Jiang, Y. P. Xu, Zhao Zhang, G. C. Xiao, Bo Li, H. Xu, Yu-Xuan Zhu, J. Z. Wang, X. H. Liang, W. Z. Zhang, L. Sun, Z. W. Li, G. H. Gao, Yanji Yang, Wan-Chang Zhang, Weiguang Cui, C. Cai, F. J. Lu, Yunchao Liu, Qingcui Bu, X. L. Cao, B. S. Liu, Bin Meng, D. K. Zhou, Y. J. Yang, Shaolin Xiong, Wenxiong Li, Tian-Xiang Chen, Lian Tao, Yi Zhang, Y. J. Zhang, M. Wu, Andrea Santangelo, XiangYang Wen, Suleimanov, H. Gao, Z. Zhang, L. D. Kong, X. Y. Song, Long Ji, W. C. Zhang, Q. B. Yi, B. Y. Wu, Mao-Shun Li, Q. Q. Yin, You-Hong Zhang, H. W. Liu, N. Sai, Da-Wei Han, J. Y. Liao, H. M. Zhang, Zhi Zhang, Ya Fang Huang, Y. F. Zhang, Min Gao, X. B. Li, B. Lu, J. L. Qu, Yi-Qiao Dong, Wenhan Jiang, Cheng-Cheng Guo, Y. S. Wang, Doroshenko, Yuan-Yuan Du, C. Z. Liu, Y X Zhu, Y. P. Chen, Sisi Yang, Y. H. Tan, J. F. Zhou, J. Jin, Xin-Fu Zhao, R. C. Shang, Xuelong Li, J. Guan, GuoQing Liu, Jia Huo, Gang Li, Lorenzo Ducci, Wei Cui, T. Zhang, Li-Ming Song, Xue-Feng Lu, Shuinai Zhang, S. M. Jia, He-Yang Liu, Y. Nang, R. L. Zhuang, J. K. Deng, C. Wang, X. H. Ma, H. S. Zhao, Ti-Pei Li, P. J. Wang, G. F. Wang, W. S. Wang, Ge Ou, Gang Chen, Yuan You, X. X. Li, and S. J. Zheng

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Accretion (astrophysics), Spectral line, Beam pattern, Neutron star, Accretion rate, Pulsar, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Polar cap, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We report on our analysis of the 2019 outburst of the X-ray accreting pulsar 4U 1901+03 observed with Insight-HXMT and NICER. Both spectra and pulse profiles evolve significantly in the decaying phase of the outburst. Dozens of flares are observed throughout the outburst. They are more frequent and brighter at the outburst peak. We find that the flares, which have a duration from tens to hundreds of seconds, are generally brighter than the persistent emission by a factor of $\sim$ 1.5. The pulse profile shape during the flares can be significantly different than that of the persistent emission. In particular, a phase shift is clearly observed in many cases. We interpret these findings as direct evidence of changes of the pulsed beam pattern, due to transitions between the sub- and super-critical accretion regimes on a short time scale. We also observe that at comparable luminosities the flares' pulse profiles are rather similar to those of the persistent emission. This indicates that the accretion on the polar cap of the neutron star is mainly determined by the luminosity, i.e., the mass accretion rate., 11 pages, 8 figures, accepted for publication in MNRAS

Published
2020

11. X-ray reprocessing in accreting pulsar GX 301-2 observed with Insight-HXMT

Author

G. H. Gao, X. X. Li, M. Wu, S. J. Zheng, Y. G. Zheng, Y. Nang, Mauro Orlandini, J. Y. Liao, H. M. Zhang, Y. L. Tuo, Y. J. Yang, R. C. Ma, Y. F. Zhang, X. B. Li, B. S. Liu, Yuan You, X. Q. Ren, Yanji Yang, Armin Nabizadeh, C. Cai, L. Chen, Tian-Xiang Chen, Wenxiong Li, Wan-Chang Zhang, W. S. Wang, Yi Zhang, Ge Ou, Andrea Santangelo, R. J. Yang, Bo Li, Peng Zhang, Qiu-Yi Luo, B. B. Wu, Cunguo Wang, H. S. Zhao, Li-Ming Song, Ming-Yu Ge, C. K. Li, F. J. Lu, Xue-Feng Lu, Y. P. Chen, Shuinai Zhang, Tong Li, Y. H. Tan, P. J. Wang, J. Y. Zhang, Victor Doroshenko, Shaolin Xiong, S. M. Jia, XiangYang Wen, Ling-Jun Wang, H. Gao, Jiren Liu, X. H. Ma, Z. W. Li, Yuan-Yuan Du, C. Z. Liu, D. K. Zhou, Sisi Yang, Ya Fang Huang, J. Jin, Xin-Fu Zhao, G. Li, Tao Luo, S. Xiao, Yu-Dong Gu, X. J. Liu, D. Gavran, X. L. Cao, Q. Q. Yin, Q. B. Yi, B. Y. Wu, V. F. Suleimanov, L. D. Kong, Y. B. Chen, X. H. Liang, L. Sun, Fuqin Zhang, S. N. Zhang, Long Ji, Z. Chang, Y. H. Zhang, Y. P. Xu, Wenhan Jiang, H. W. Liu, N. Sai, Y. S. Wang, W. C. Zhang, Xuelong Li, J. Guan, Lian Tao, Cheng-Cheng Guo, X. Y. Song, Jia Huo, Lorenzo Ducci, J. Y. Nie, Bin Meng, Wei Cui, G. C. Xiao, Qingcui Bu, Da-Wei Han, J. L. Qu, Hongfei Liu, ITA, DEU, and CHN

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Accretion (meteorology), Astrophysics::High Energy Astrophysical Phenomena, X-ray, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Radiation, 01 natural sciences, Neutron star, Pulsar, Space and Planetary Science, Ionization, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010306 general physics, Absorption (electromagnetic radiation), Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Equivalent width, Astrophysics::Galaxy Astrophysics
Abstract

We investigate the absorption and emission features in observations of GX 301-2 detected with Insight-HXMT/LE in 2017-2019. At different orbital phases, we found prominent Fe Kalpha, Kbeta and Ni Kalpha lines, as well as Compton shoulders and Fe K-shell absorption edges. These features are due to the X-ray reprocessing caused by the interaction between the radiation from the source and surrounding accretion material. According to the ratio of iron lines Kalpha and Kbeta, we infer the accretion material is in a low ionisation state. We find an orbital-dependent local absorption column density, which has a large value and strong variability around the periastron. We explain its variability as a result of inhomogeneities of the accretion environment and/or instabilities of accretion processes. In addition, the variable local column density is correlated with the equivalent width of the iron Kalpha lines throughout the orbit, which suggests that the accretion material near the neutron star is spherically distributed., Comment: 10 pages, 5 figures, 2 tables, accepted for publication in MNRAS

Published
2020
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12. Hot disk of the Swift J0243.6+6124 revealed by Insight-HXMT

Author

J. K. Deng, X. H. Ma, B. B. Wu, Min Gao, Lian Tao, L. Chen, Yi-Yan Yang, X. Y. Song, C. L. Zhang, Xue-Feng Lu, Shuinai Zhang, H. S. Zhao, S. M. Jia, C. Z. Liu, M. X. Fu, Y. Nang, Ya Fang Huang, Tao Luo, Wan-Chang Zhang, Bin Meng, Mao-Shun Li, Sisi Yang, X. X. Li, L. J. Qu, J. Z. Wang, Y. L. Tuo, G. F. Wang, J. W. Yang, W. C. Jiang, Tian-Xiang Chen, Weiguang Cui, Qingcui Bu, Yunchao Liu, Y. J. Jin, L. M. Song, Sergey S. Tsygankov, Y. J. Yang, V. Doroshenko, Ti-Pei Li, F. Zhang, Yuan-Yuan Du, S. J. Zheng, Gang Chen, W. S. Wang, J. Y. Liao, H. M. Zhang, Junke Zhang, Wenxiong Li, Qing-He Zhang, Ge Ou, Da-Wei Han, XiangYang Wen, J. Y. Nie, Y. F. Zhang, Andrea Santangelo, Shaolin Xiong, Bo Lu, J. Jin, Y. J. Zhang, Xuchao Zhao, H. Gao, W. Z. Zhang, Wei Zhang, G. H. Gao, Yi-Qiao Dong, Y. H. Tan, Cheng-Cheng Guo, M. Wu, Y. Zhang, Fangjun Lu, Y. B. Chen, Alexander A. Mushtukov, Z. Zhang, Long Ji, Y. P. Chen, Bing Li, Y. S. Wang, T. Zhang, Chun-sheng Zhang, Xiaobo Li, W. Hu, X. F. Li, X. H. Liang, C. L. Zou, Z. L. Zhang, C. K. Li, G. C. Xiao, H. Xu, Y. X. Zhu, Z. W. Li, Ming-Yu Ge, Z. J. Li, ShaoZhen Liu, L. D. Kong, Yidong Xu, Yu-Dong Gu, S. N. Zhang, Jia Huo, Gang Li, X. L. Cao, J. Zhao, J. Guan, Aimei Zhang, GuoQing Liu, Wei Cui, Yu-Xuan Zhu, X. J. Liu, Liang Sun, Y. G. Li, Luhua Jiang, Z. Chang, Yujuan Liu, H. W. Liu, and N. Sai

Subjects
Swift, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetosphere, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Pulsar, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, computer.programming_language, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Scattering, Spectral properties, Astronomy and Astrophysics, Accretion (astrophysics), Neutron star, Radiation pressure, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, computer
Abstract

We report on analysis of observations of the bright transient X-ray pulsar \src obtained during its 2017-2018 giant outburst with Insight-HXMT, \emph{NuSTAR}, and \textit{Swift} observatories. We focus on the discovery of a sharp state transition of the timing and spectral properties of the source at super-Eddington accretion rates, which we associate with the transition of the accretion disk to a radiation pressure dominated (RPD) state, the first ever directly observed for magnetized neutron star. This transition occurs at slightly higher luminosity compared to already reported transition of the source from sub- to super-critical accretion regime associate with onset of an accretion column. We argue that this scenario can only be realized for comparatively weakly magnetized neutron star, not dissimilar to other ultra-luminous X-ray pulsars (ULPs), which accrete at similar rates. Further evidence for this conclusion is provided by the non-detection of the transition to the propeller state in quiescence which strongly implies compact magnetosphere and thus rules out magnetar-like fields., Submitted to MNRAS

Published
2019
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13. Insight-HXMT observations of Swift J0243.6+6124 during its 2017-2018 outburst

Author

Min-Xue Fu, Yanguo Li, Y. N. Liu, Li-Ming Song, Yu-Sa Wang, Jianling Zhao, Wan-Chang Zhang, Victor Doroshenko, Wei Zhang, Xue-Feng Lu, Xiaobo Li, Zi-Liang Zhang, Cheng-Cheng Guo, Da-Wei Han, YongJie Jin, He Xu, C. L. Zou, C. L. Zhang, HongMei Zhang, Guang-Cheng Xiao, Yongwei Dong, Juan Zhang, Yifei Zhang, Li Chen, Can Güngör, ZiJian Li, Yue Zhang, ShaoZhen Liu, Jin-Yuan Liao, ChunLei Zhang, Jianyin Nie, Jing-Kang Deng, Shu Zhang, Yu-Dong Gu, Wei Hu, Tong Zhang, Ming-Yu Ge, Xiao-Jing Liu, Y. Nang, LuHua Jiang, Jin-Lu Qu, M. Gao, Yue Zhu, Xufang Li, J. W. Yang, Bo Lu, Xiao-Fan Zhao, Cheng-Kui Li, Ju Guan, Youli Tuo, Huanyu Wang, Changsheng Shi, T. Luo, Andrea Santangelo, G. F. Wang, Xiang Ma, Yongjie Zhang, N. Sai, Zheng-Wei Li, Hai-Sheng Zhao, W. C. Jiang, Bin Meng, Lian Tao, Gang Chen, Wei-Wei Cui, Ying Tan, Yue Huang, Shaolin Xiong, Tian-Xiang Chen, Wei Li, Zhao Zhang, Guan-Hua Gao, Shu-Mei Jia, Bobing Wu, W. Z. Zhang, W. S. Wang, Zhi Chang, Ge Ou, Liang Sun, Y. P. Chen, C. X. Liu, Bing Li, Yupeng Xu, Jing Jin, WenHui Tao, Juan Wang, H. T. Liu, Mao-Shun Li, L. L. Yan, ShiJie Zheng, Yanji Yang, Yuan-Yuan Du, Mei Wu, XiangYang Wen, Yi Zhang, Xian Li, Sheng Yang, Wei Cui, GuoQing Liu, Jia Huo, Yuan Liu, Gang Li, Long Ji, X. H. Liang, He Gao, Shuang-Nan Zhang, Aimei Zhang, Yong Chen, Fan Zhang, and Yu-Xuan Zhu

Subjects
Physics, Swift, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Accretion (astrophysics), Accretion disc, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, computer, Astrophysics::Galaxy Astrophysics, computer.programming_language
Abstract

The recently discovered neutron star transient Swift J0243.6+6124 has been monitored by {\it the Hard X-ray Modulation Telescope} ({\it Insight-\rm HXMT). Based on the obtained data, we investigate the broadband spectrum of the source throughout the outburst. We estimate the broadband flux of the source and search for possible cyclotron line in the broadband spectrum. No evidence of line-like features is, however, found up to $\rm 150~keV$. In the absence of any cyclotron line in its energy spectrum, we estimate the magnetic field of the source based on the observed spin evolution of the neutron star by applying two accretion torque models. In both cases, we get consistent results with $B\rm \sim 10^{13}~G$, $D\rm \sim 6~kpc$ and peak luminosity of $\rm >10^{39}~erg~s^{-1}$ which makes the source the first Galactic ultraluminous X-ray source hosting a neutron star., published

Published
2019
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14. Insight-HXMT observations of the New Black Hole Candidate MAXI J1535-571: timing analysis

Author

Wei Zhang, Yi-Qiao Dong, Cheng-Cheng Guo, X. L. Cao, Fu-Guo Xie, Xian Hou, Yupeng Xu, Jiancheng Wang, Xian Li, Jundan Nie, Y. G. Li, Yunchao Liu, Z. Chang, Yujuan Liu, C. L. Zou, Luhua Jiang, Y. J. Yang, W. C. Jiang, C. Z. Liu, Wei Cui, Mao-Shun Li, J. K. Deng, J. F. Zhou, Tianmeng Zhang, B. B. Wu, Jia Huo, X. H. Ma, Ju Guan, J. F. Ji, Xiaobo Li, ShaoZhen Liu, Tianran Chen, Shan-Shan Weng, Gang Chen, Yu-Dong Gu, Lian Tao, Y. X. Zhu, Li-Ming Song, Ming-Yu Ge, Xiao-Jing Liu, Bing Li, Guobao Zhang, Xue-Feng Lu, H. W. Liu, Shuinai Zhang, W. Z. Zhang, Yuan-Yuan Du, Z. L. Zhang, Y. S. Wang, Wenxiong Li, GuoQing Liu, Y. H. Tan, L. Chen, Wenfei Yu, Hsiang-Kuang Chang, S. N. Zhang, Chuan-Peng Zhang, Ya Fang Huang, Y. Nang, C. L. Zhang, Limei Yan, S. Yang, G. H. Gao, Wan-Chang Zhang, Y. P. Chen, Can Güngör, Y. B. Chen, Ti-Pei Li, M. Wu, Y. Zhang, G. F. Wang, Y. L. Tuo, J. Y. Liao, H. M. Zhang, J. W. Yang, Y. F. Zhang, Bo Lu, Xuchao Zhao, M. X. Fu, Jia Zhang, C. K. Li, H. Wang, Wei Hu, Z. Zhang, X. X. Li, Weiguang Cui, Qing-He Zhang, Zhuo Li, Qingcui Bu, Shu-Mei Jia, W. S. Wang, Shaolin Xiong, HongSheng Zhao, H. Xu, Ge Ou, Y. J. Zhang, Z. W. Li, Da-Wei Han, H. Gao, S. J. Zheng, Tao Luo, X. H. Liang, Min Gao, J. Zhao, J. L. Qu, Liang Sun, Albert K. H. Kong, Aimei Zhang, Gang Li, N. Sai, Yu-Xuan Zhu, Bin Meng, Fangjun Lu, Y. J. Jin, J. Jin, R. C. Shang, WenHui Tao, G. C. Xiao, F. Zhang, and XiangYang Wen

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Static timing analysis, Centroid, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Phase lag, law.invention, Black hole, Telescope, Amplitude, Space and Planetary Science, law, 0103 physical sciences, Modulation (music), Intermediate state, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics
Abstract

We present the X-ray timing results of the new black hole candidate (BHC) MAXI J1535-571 during its 2017 outburst from Hard X-ray Modulation Telescope (\emph{Insight}-HXMT) observations taken from 2017 September 6 to 23. Following the definitions given by \citet{Belloni2010}, we find that the source exhibits state transitions from Low/Hard state (LHS) to Hard Intermediate state (HIMS) and eventually to Soft Intermediate state (SIMS). Quasi-periodic oscillations (QPOs) are found in the intermediate states, which suggest different types of QPOs. With the large effective area of \emph{Insight}-HXMT at high energies, we are able to present the energy dependence of the QPO amplitude and centroid frequency up to 100 keV which is rarely explored by previous satellites. We also find that the phase lag at the type-C QPOs centroid frequency is negative (soft lags) and strongly correlated with the centroid frequency. By assuming a geometrical origin of type-C QPOs, the source is consistent with being a high inclination system., Comment: 12 pages, 11 figures, Sumbitted to ApJ

Published
2018
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15. Insight-HXMT observations of the first binary neutron star merger GW170817

Author

Xufang Li, C. L. Zou, Yongjie Zhang, Yifei Zhang, Lian Tao, N. Sai, Ti-Pei Li, Shuang-Nan Zhang, Bin Meng, Aimei Zhang, Tong Zhang, Ming-Yu Ge, Xiao-Jing Liu, Yupeng Xu, Yuan Liu, Jing Jin, J. W. Yang, ShaoZhen Liu, Guan-Hua Gao, Xian Li, Sheng Yang, X. L. Cao, G. C. Xiao, Yong Chen, LinLi Yan, Shu-Mei Jia, Y. Tan, XiangYang Wen, W. C. Jiang, Yu-Dong Gu, Zheng-Wei Li, LuHua Jiang, L. Chen, M. X. Fu, W. S. Wang, Huanyu Wang, Wei-Wei Cui, Jianling Zhao, Yue Zhang, Yanji Yang, Juan Zhang, Yu-Xuan Zhu, Mao-Shun Li, Tian-Xiang Chen, Shaolin Xiong, Ju Guan, Jianyin Nie, Ge Ou, Wei Li, Cheng-Cheng Guo, Liang Sun, Bing Li, Wei Cui, Cheng-Kui Li, Yu-Peng Chen, Fan Zhang, H. Gao, Jin-Lu Qu, Yi Zhang, Yuan-Yuan Du, Wei Hu, Xiao-Fan Zhao, Yongwei Dong, Yue Huang, Gang Chen, X. H. Liang, Yue Zhu, Fangjun Lu, WenHui Tao, Hai-Sheng Zhao, He Xu, Juan Wang, H. T. Liu, Y. B. Chen, Youli Tuo, T. Luo, Jia Huo, W. Z. Zhang, ZiJian Li, Zhao Zhang, Gang Li, Yu-Sa Wang, Mei Wu, Shu Zhang, J. Y. Liao, Wei Zhang, Bo Lu, Y. N. Liu, Zi-Liang Zhang, Zhi Chang, GuoQing Liu, Da-Wei Han, HongMei Zhang, YongJie Jin, Y. Nang, ChunLei Zhang, G. F. Wang, Xiang Ma, Yanguo Li, Li-Ming Song, Xue-Feng Lu, M. Gao, Shi-Jie Zheng, Qiang Zhang, Bobing Wu, C. L. Zhang, C. X. Liu, J. K. Deng, Wan-Chang Zhang, and Xiaobo Li

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, General Physics and Astronomy, FOS: Physical sciences, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Compact star, 01 natural sciences, LIGO, law.invention, Telescope, Neutron star, law, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, 010306 general physics, Gamma-ray burst, 010303 astronomy & astrophysics, Fermi Gamma-ray Space Telescope
Abstract

Finding the electromagnetic (EM) counterpart of binary compact star merger, especially the binary neutron star (BNS) merger, is critically important for gravitational wave (GW) astronomy, cosmology and fundamental physics. On Aug. 17, 2017, Advanced LIGO and \textit{Fermi}/GBM independently triggered the first BNS merger, GW170817, and its high energy EM counterpart, GRB 170817A, respectively, resulting in a global observation campaign covering gamma-ray, X-ray, UV, optical, IR, radio as well as neutrinos. The High Energy X-ray telescope (HE) onboard \textit{Insight}-HXMT (Hard X-ray Modulation Telescope) is the unique high-energy gamma-ray telescope that monitored the entire GW localization area and especially the optical counterpart (SSS17a/AT2017gfo) with very large collection area ($\sim$1000 cm$^2$) and microsecond time resolution in 0.2-5 MeV. In addition, \textit{Insight}-HXMT quickly implemented a Target of Opportunity (ToO) observation to scan the GW localization area for potential X-ray emission from the GW source. Although it did not detect any significant high energy (0.2-5 MeV) radiation from GW170817, its observation helped to confirm the unexpected weak and soft nature of GRB 170817A. Meanwhile, \textit{Insight}-HXMT/HE provides one of the most stringent constraints (~10$^{-7}$ to 10$^{-6}$ erg/cm$^2$/s) for both GRB170817A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger. Therefore the observation of \textit{Insight}-HXMT constitutes an important chapter in the full context of multi-wavelength and multi-messenger observation of this historical GW event., Comment: accepted by Science China - Physics, Mechanics & Astronomy. Planned to publish on Oct 17, but postponed due to a problem on pdf file

Published
2017
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16. A modified topographic index that incorporates the hydraulic and physical properties of soil.

Author

Lu Yi, Wan-Chang Zhang, and Chang-An Yan

Subjects
*SOIL permeability, *RUNOFF, *SOIL erosion, *HYDROLOGIC models, *HUMIDITY
Abstract

Aiming at quantifying the impacts of soil properties on rainfall-runoff processes, the soil saturated hydraulic conductivity (Ks) and the soil erodibility factor (K) were selected and incorporated into the classical topographic index ln(α/tanβ) (TI) to construct a modified topographic index (TI0). Stream network extractions and performance evaluations of topography-based hydrological models based on TI and TI' were carried out in three watersheds with different climate conditions. The investigations indicated that: (1) the changes of stream networks caused by the incorporation of Ks·K could correctly present the phenomenon that the points would show greater potential to be saturated to become contributing areas if their underlying soils possess higher hydraulic conductivities and stronger erodibility; and (2) the performances of the topography-based hydrological models TOPMODEL and TOPX were improved when simulating the daily rainfall-runoff processes with the input of ln(α/(tanβ·Ks·K) (TI3). TI3 was suitable for rainfall-runoff simulation in arid and semi-arid, humid and semi-humid, and humid regions. The performance improvements increased as the spatial heterogeneity of Ks·K enlarged. Based on these investigations, TI3 was recommended for the modified form of TI'. [ABSTRACT FROM AUTHOR]

Published
2017
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