Insight-HXMT, China’s first astronomical space X-ray satellite, has detected a low-frequency quasi-periodic oscillation (QPO) over 200 kiloelectron volts (keV) in a black hole binary, which makes it the most energetic low frequency QPO ever found. The scientists also found that the QPO originated from the precession of a relativistic jet (high-speed outward motion) plasma Strom) near the black hole’s event horizon. These discoveries have important implications for resolving the longstanding debate about the physical origin of low-frequency QPOs.
This work, published online in Natural astronomy on September 21, 2020 was primarily carried out by scientists from the Institute for High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS), the University of Southampton (Great Britain), the Eberhard Karls University of Tübingen (Germany) and the Shanghai Astronomical Observatory by CAS .
Low frequency QPOs, discovered in the 1980s, are a common feature of the time of observation in transient black hole binaries. They are quasi-periodic, but not exactly periodic modulations in light curves. The origin of low-frequency QPOs was unknown for over 30 years. The two most popular models that explain their origin are: 1) The vibrations are caused by the instability of the accretion disk as matter rotates and eventually falls into the black hole. and 2) the quasi-periodic X-ray modulations are generated by the oscillation or precession of the coronal X-ray emission region near the black hole.
Before the era of Insight-HXMT, X-ray satellites could only detect and examine low-frequency QPOs below 30 keV. So it was difficult to test these models. Insight-HXMT, on the other hand, has a wide effective energy range of 1-250 keV and the largest effective area over 30 keV. So after the launch of Insight-HXMT, scientists expected it to be able to detect rich, low-frequency QPOs above 30 keV and thus fully test previous models.
The new black hole X-ray binary system MAXI J1820 + 070, consisting of a black hole with several solar masses and a companion star, began an eruption on March 11, 2018. It was one of the brightest X-ray sources in the sky for a long time. Insight-HXMT responded quickly and performed high cadence observations on this source for several months, collecting a large amount of observational data.
Based on these data, the scientists found that MAXI J1820 + 070’s low-frequency QPO occurred in a wide energy range and its maximum detection energy exceeded 200 keV, which is almost an order of magnitude higher than previous QPOs observed by other telescopes. This indicates that the QPO could not originate from the thermal radiation area of the accretion disk. Further studies showed that the frequency and the variability amplitude of the QPO are energy-independent and that the high-energy QPO precedes the low-energy one.
These results clearly contradicted most of the models currently in existence. Therefore, the scientists suggested that the low-frequency QPO was created by the precession of a beam near the black hole’s event horizon. The precession was likely caused by the frame drag effect of general relativity created by the rotation of the black hole.
Jets are high-speed streams of matter that move almost at the speed of light. Numerous jets have been observed in black hole binaries and distant quasars that host supermassive black holes (that is, those of millions to ten billion solar masses) in the radio, optical, and X-ray bands. Jets are an important observation feature of black hole systems and the primary means by which black holes affect the environment by feedback from swallowing nearby matter.
However, these jets are far from black holes. They are typically more than a million times the black hole’s event horizon. At such a great distance, the black hole’s gravitational force actually has no effect. Therefore, it is unclear where these jets are created, how far they are from the black holes, how they can escape the black holes’ strong gravitational field, and how they are accelerated to a speed close to the speed of light.
The Insight-HXMT discovery is particularly important because it is the first time a jet has been found hundreds of kilometers from a black hole (i.e. several times the black hole’s event horizon). As the next relativistic ray that has so far been observed in a black hole, the finding is of great importance for the investigation of the relativistic effects, dynamic processes and radiation mechanisms.
Reference: “Detection of vibrations above 200 keV in a black hole X-ray binary with Insight-HXMT” by Xiang Ma, Lian Tao, Shuang-Nan Zhang, Liang Zhang, Qing-Cui Bu, Ming-Yu Ge and Yu-Peng Chen, Jin -Lu Qu, Shu Zhang, Fang-Jun Lu, Li-Ming-Lied, Yi-Jung Yang, Feng Yuan, Ce Cai, Xue-Lei Cao, Zhi Chang, Gang Chen, Li Chen, Tian-Xiang Chen, Yi- Bao Chen, Yong Chen, Wei Cui, Wei-Wei Cui, Jing-Kang Deng, Yong-Wei Dong, Yuan-Yuan Du, Min-Xue Fu, Guan-Hua Gao, He Gao, Min Gao, Yu-Dong Gu, Ju Guan, Cheng-Cheng Guo, Da-Wei Han, Yue Huang, Jia Huo, Long Ji, Shu-Mei Jia, Lu-Hua Jiang, Wei-Chun Jiang, Jing Jin, Yong-Jie Jin, Ling-Da Kong, Bing Li, Cheng-Kui Li, Gang Li, Mao-Shun Li, Ti-Pei Li, Wei Li, Xian Li, Xiao-Bo Li, Xu-Fang Li, Yan-Guo Li, Zheng-Wei Li, Xiao -Hua Liang, Jin-Yuan Liao, Bai-Sheng Liu, Cong-Zhan Liu, Guo-Qing Liu, Hong-Wei Liu, Xiao-Jing Liu, Yi-Nong Liu, Bo Lu, Xue-Feng Lu, Qi Luo, Tao Luo , Bin Meng, Yi Nang, Jian-Yin Nie, Ge Ou, Na Sai, Ren-Cheng Shang, Xin-Ying-Lied, Lian g Sun, Yi ng Tan, Yuo-Li Tuo, Chen Wang, Guo-Feng Wang, Juan Wang, Ling-Jun Wang, Wen-Shuai Wang, Yu-Sa Wang, Xiang-Yang Wen, Bai-Yang Wu, Bo- Bing Wu, Mei Wu, Guang-Cheng Xiao, Shuo Xiao, Fu-Guo Xie, Shao-Lin Xiong, He Xu, Yu-Peng Xu, Jia-Wei Yang, Sheng Yang, Yan-Ji Yang, Qi-Bin Yi, Qian-Qing Yin, Yuan You, Ai-Mei Zhang, Cheng-Mo Zhang, Fan Zhang, Hong-Mei Zhang, Juan Zhang, Tong Zhang, Wan-Chang Zhang, Wei Zhang, Wen-Zhao Zhang, Yi Zhang, Yi- Fei Zhang, Yong-Jie Zhang, Yue Zhang, Zhao Zhang, Zhi Zhang, Zi-Liang Zhang, Hai-Sheng Zhao, Xiao-Fan Zhao, Shi-Jie Zheng, Deng-Ke Zhou, Jian-Feng Zhou, Yu-Xuan Zhu, Yue Zhu and Ren-Lin Zhuang, September 21, 2020 Natural astronomy on.
DOI: 10.1038 / s41550-020-1192-2
The Institute of High Energy Physics proposed the Insight HXMT satellite project and is leading the development of its payloads, ground application system and scientific research. The China Academy of Space Technology, Tsinghua University, the CAS National Space Science Center and Beijing Normal University have also participated in the project and made important contributions.