학술논문
Insight-HXMT observations of a possible fast transition from jet to wind dominated state during a huge flare of GRS~1915+105
Document Type
Working Paper
Author
Kong, L. D.; Zhang, S.; Chen, Y. P.; Zhang, S. N.; Ji, L.; Wang, P. J.; Tao, L.; Ge, M. Y.; Liu, C. Z.; Song, L. M.; Lu, F. J.; Qu, J. L.; Li, T. P.; Xu, Y. P.; Cao, X. L.; Chen, Y.; Bu, Q. C.; Cai, C.; Chang, Z.; Chen, G.; Chen, L.; Chen, T. X.; Cui, W. W.; Du, Y. Y.; Gao, G. H.; Gao, H.; Gao, M.; Gu, Y. D.; Guan, J.; Guo, C. C.; Han, D. W.; Huang, Y.; Huo, J.; Jia, S. M.; Jiang, W. C.; Jin, J.; Li, B.; Li, C. K.; Li, G.; Li, W.; Li, X.; Li, X. B.; Li, X. F.; Li, Z. W.; Liang, X. H.; Liao, J. Y.; Liu, B. S.; Liu, H. W.; Liu, H. X.; Liu, X. J.; Lu, X. F.; Luo, Q.; Luo, T.; Ma, R. C.; Ma, X.; Meng, B.; Nang, Y.; Nie, J. Y.; Ou, G.; Ren, X. Q.; Sai, N.; Song, X. Y.; Sun, L.; Tan, Y.; Tuo, Y. L.; Wang, C.; Wang, L. J.; Wang, W. S.; Wang, Y. S.; Wen, X. Y.; Wu, B. B.; Wu, B. Y.; Wu, M.; Xiao, G. C.; Xiao, S.; Xiong, S. L.; Yang, R. J.; Yang, S.; Yang, Y. J.; Yi, Q. B.; Yin, Q. Q.; You, Y.; Zhang, F.; Zhang, H. M.; Zhang, J.; Zhang, P.; Zhang, W. C.; Zhang, W.; Zhang, Y. F.; Zhang, Y. H.; Zhao, H. S.; Zhao, X. F.; Zheng, S. J.; Zheng, Y. G.; Zhou, D. K.
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Abstract
We present the analysis of the brightest flare that was recorded in the \emph{Insight}-HMXT data set, in a broad energy range (2$-$200 keV) from the microquasar GRS~1915+105 during an unusual low-luminosity state. This flare was detected by \emph{Insight}-HXMT among a series of flares during 2 June 2019 UTC 16:37:06 to 20:11:36, with a 2-200 keV luminosity of 3.4$-$7.27$\times10^{38}$ erg s$^{-1}$. Basing on the broad-band spectral analysis, we find that the flare spectrum shows different behaviors during bright and faint epochs. The spectrum of the flare can be fitted with a model dominated by a power-law component. Additional components show up in the bright epoch with a hard tail and in the faint epoch with an absorption line $\sim$ 6.78 keV. The reflection component of the latter is consistent with an inner disk radius $\sim$ 5 times larger than that of the former. These results on the giant flare during the "unusual" low-luminosity state of GRS~1915+105 may suggest that the source experiences a possible fast transition from a jet-dominated state to a wind-dominated state. We speculate that the evolving accretion disk and the large-scale magnetic field may play important roles in this peculiar huge flare.