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1. 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

2. 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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3. 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

4. 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

5. 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

6. 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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7. 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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