Year: 2026
Type: preprint
Abstract: We report a day-scale hard lag between GeV and TeV $γ$-ray emission from the HBL 1ES~1959+650 in early 2024. Since the LHAASO-WCDA real-time monitoring system began operation in late 2023, multiple TeV flares from this source have been triggered, including the 1st trigger flare on 2024 February 9. A Bayesian-block analysis of the WCDA light curve identifies three TeV flares in 2024. For the second triggered flare, a discrete cross-correlation analysis reveals a $>3\,σ$ correlation (relative to uncorrelated red-noise simulations) at a time delay of $Δt = 5.0_{-2.1}^{+2.1}$ days, with the TeV emission lagging the GeV. Time-resolved spectroscopy shows that this flare has the softest TeV spectrum among these flares (intrinsic spectral index $Γ=3.16\pm0.18$), while the 1st trigger flare is harder ($Γ=2.48\pm0.21$). The observed five-day hard lag is difficult to reconcile with a purely cooling-driven temporal ordering and is consistent with scenarios in which particle energization and/or transport may contribute to the evolution. However, the current data do not uniquely identify the underlying mechanism.
Source: arXiv (Cornell University)
Authors: Cao, Zhen, Aharonian, F., Bai, Y. X., Bao, Y. W., Bastieri, D., Bi, X. J., Bi, Y. J., Bian, W., Blunier, J., Bukevich, A. V., Cai, C. M., Cao, W. Y., Cao, Zhe, Chang, J., Chang, J. F., Chen, E. S., Chen, G. H., Chen, H. K., Chen, L. F., Chen, Liang, Chen, Long, Chen, M. J., Chen, M. L., Chen, Q. H., Chen, S., Chen, S. H., Chen, S. Z., Chen, T. L., Chen, X. B., Chen, X. J., Chen, X. P., Chen, Yang, Chen, Yong, Cheng, N., Cheng, Q. Y., Cheng, Y. D., Chi, Y. H., Cui, M. Y., Cui, S. W., Cui, X. H., Cui, Y. D., Dai, B. Z., Dai, H. L., Dai, L. X., Dai, Z. G., Danzengluobu, Diao, Y. X., Dong, A. J., Duan, X. D., Fan, J. H., Fan, Y. Z., Fang, J., Fang, J. H., Fang, K., Feng, C. F., Feng, H., Feng, L., Feng, S. H., Feng, X. T., Feng, Y., Feng, Y. L., Gabici, S., Gao, B., Gao, Q., Gao, W., Ge, C., Ge, M. M., Ge, T. T., Geng, L. S., Giacinti, G., Gong, G. H., Gou, Q. B., Gu, M. H., Gu, W. M., Guo, F. L., Guo, J., Guo, K. J., Guo, X. L., Guo, Y. Q., Han, R. P., Hannuksela, O. A., Hasan, M., He, H. H., He, H. N., He, J. Y., He, X. Y., He, Y., Hernández-Cadena, S., Hou, C., Hou, X., Hu, H. B., Hu, S. C., Huang, D. H., Huang, F., Huang, J. J., Huang, X. L., Huang, X. T., Huang, X. Y., Huang, Y., Huang, Z. J., Inventar, A., Ji, X. L., Jia, H. Y., Jia, K., Jia, S. M., Jiang, H. B., Jiang, K., Jiang, X. W., Jiang, Z. J., Jin, C. C., Jin, M., Kaci, S., Kang, M. M., Karpikov, I., Khangulyan, D., Kuleshov, D., Kurinov, K., Lei, W. H., Li, Cheng, Li, C. K., Li, Cong, Li, D., Li, F., Li, H. B., Li, H. C., Li, Jian, Li, Jie, Li, K., Li, L., Li, R. L., Li, T. Y., Li, W. L., Li, X. R., Li, X. Y., Li, Y., Li, Zhe, Li, Zhuo, Liang, E. W., Liang, Y. F., Lin, S. J., Liu, B., Liu, C., Liu, D., Liu, D. B., Liu, H., Liu, J., Liu, J. L., Liu, J. R., Liu, M. Y., Liu, Q., Liu, R. Y., Liu, S. M., Liu, T., Liu, W., Liu, Y., Liu, Y., Liu, Yuan, Liu, Y. N., Lou, Y. Q., Luo, Q., Luo, Y., Lv, H. K., Ma, B. Q., Ma, L. L., Ma, X. H., Maliy, I. O., Mao, J. R., Min, Z., Mitthumsiri, W., Mizuno, Y., Mou, G. B., Neronov, A., Ng, C. -Y., Ng, K. C. Y., Ni, M. Y., Nie, L., Ou, L. J., Ou, Z. W., Pan, H. W., Pattarakijwanich, P., Pei, Z. Y., Peng, D. Y., Qi, J. C., Qi, M. Y., Qin, J. J., Qu, H., Raza, A., Ren, C. Y., Ruan, M. Q., Ruffolo, D., Sáiz, A., Savchenko, D., Semikoz, D., Shao, L., Shchegolev, O., Shen, Y. Z., Sheng, X. D., Shu, F. W., Song, H. C., Stenkin, Yu. V., Su, Y., Sun, C. Y., Sun, D. X., Sun, H., Sun, J. X., Sun, M., Sun, Q. N., Sun, X. N., Sun, Z. B., Tabasam, N. H., Takata, J., Tam, P. H. T., Tan, H. B., Tang, Q. W., Tang, R., Tang, Z. B., Tao, L., Tian, W. W., Tong, C. N., Wan, L. H., Wang, C., Wang, D. H., Wang, G. W., Wang, H. G., Wang, J. C., Wang, J. F., Wang, J. S., Wang, K., Wang, Kai, Wang, Kai, Wang, L. P., Wang, L. Y., Wang, W., Wang, X. G., Wang, X. J., Wang, X. Y., Wang, Y., Wang, Y. D., Wang, Z. H., Wang, Z. X., Wang, Zheng, Wei, D. M., Wei, J. J., Wei, Y. J., Wen, T., Weng, S. S., Wu, C. Y., Wu, H. R., Wu, Q. W., Wu, S., Wu, X. F., Wu, Y. S., Xi, S. Q., Xia, J., Xiang, G. M., Xiao, D. X., Xiao, G., Xiao, Y. F., Xie, B. H., Xie, F., Xin, Y. L., Xing, H. D., Xing, Y., Xiong, D. R., Xu, B. N., Xu, C. Y., Xu, D. L., Xu, R. X., Xu, S. S., Xue, L., Yan, D. H., Yan, T., Yang, C., Yang, C. Y., Yang, F. F., Yang, L. L., Yang, M. J., Yang, R. Z., Yang, W. X., Yang, Z. H., Yao, Z. G., Ye, X. A., Yin, L. Q., Yin, N., You, X. H., You, Z. Y., Yu, Y. H., Yuan, Q., Yuan, W. M., Yue, H., Zeng, H. D., Zeng, T. X., Zeng, W., Zeng, X. T., Zha, M., Zhang, B., Zhang, B. B., Zhang, B. T., Zhang, C., Zhang, H., Zhang, H. M., Zhang, H. Y., Zhang, J., Zhang, J. L., Zhang, J. Y., Zhang, L. Y., Zhang, Li, Zhang, P. F., Zhang, R., Zhang, R. Y., Zhang, S. R., Zhang, S. S., Zhang, S. Y., Zhang, W., Zhang, X., Zhang, X. L., Zhang, X. P., Zhang, Yi, Zhang, Yong, Zhang, Z. P., Zhao, H. S., Zhao, J., Zhao, L., Zhao, L. Z., Zhao, X. H., Zheng, F., Zheng, T. C., Zhou, B., Zhou, H., Zhou, J. N., Zhou, L., Zhou, M., Zhou, P., Zhou, R., Zhou, X. X., Zhou, X. X., Zhu, B. Y., Zhu, C. G., Zhu, F. R., Zhu, H., Zhu, K. J., Zhu, Y. F., Zhu, Z. F., Zou, Y. C., Zuo, X.
Institutions: Chinese Academy of Sciences, Institute of High Energy Physics, Shanghai Jiao Tong University, Guangzhou University, Southwest Jiaotong University, Centre National de la Recherche Scientifique, Université Paris Cité, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Observatoire de Paris, Laboratoire AstroParticule et Cosmologie, Institut National de Physique Nucléaire et de Physique des Particules, Institut de Recherche sur les Lois Fondamentales de l'Univers, Institute for Nuclear Research, Chinese University of Hong Kong, Hebei Normal University, Shanghai Astronomical Observatory, Yunnan University, Tibet University, Purple Mountain Observatory, Nanjing University, National Astronomical Observatories, Sun Yat-sen University, University of Science and Technology of China, Guizhou Normal University, Henan Normal University, Zhejiang Lab, Shandong University, Xiamen University, University of Hong Kong, Tsinghua University, University of Chinese Academy of Sciences
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Natural Science Foundation of China, Chinese Academy of Sciences, National Science and Technology Development Agency, National Research Council of Thailand, Youth Innovation Promotion Association of the Chinese Academy of Sciences, Department of Science and Technology of Sichuan Province, Youth Innovation Promotion Association
OpenAlex ID: W7207789438