LEIA discovery of the longest-lasting and most energetic stellar X-ray flare ever detected

Xuan Mao; He-Yang Liu; Song Wang; Zhixing Ling; Weimin Yuan; Huaqing Cheng; Haiwu Pan; Dongyue Li; Fabio Favata; Tuo Ji; Jujia Zhang; Xinlin Zhao; Jing Wan; Zhiming Cai; Alberto J. Castro-Tirado; Yanfeng Dai; Licai Deng; Xu Ding; Kaifan Ji; Chichuan Jin; Yajuan Lei; Huali Li; Jun Lin; Huaqiu Liu; Mingjun Liu; Shuai Liu; Yuan Liu; Hui Sun; Shengli Sun; Xiaojin Sun; Jianrong Shi; Jianguo Wang; Jingxiu Wang; Wenxin Wang; Jianyan Wei; Liping Xin; Dingrong Xiong; Chen Zhang; Wenda Zhang; Yonghe Zhang; Xiaofeng Zhang; Donghua Zhao; Guiping Zhou

arXiv · 2410.17999

LEIA discovery of the longest-lasting and most energetic stellar X-ray flare ever detected

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Abstract

The Lobster Eye Imager for Astronomy (LEIA) detected a new X-ray transient on 2022 November 7, identified as a superflare event occurring on a nearby K-type giant star HD 251108. The flux increase was also detected in follow-up observations at X-ray, UV and optical wavelengths. The flare lasted for about 40 days in soft X-ray observations, reaching a peak luminosity of ~1.1 * 10^34 erg/s in 0.5-4.0 keV, which is roughly 60 times the quiescent luminosity. Optical brightening was observed for only one night. The X-ray light curve is well described by a double fast rise and exponential decay model, attributed to the cooling process of a loop arcade structure formed subsequent to the initial large loop with a half-length of ~1.9 * 10^12 cm. Time-resolved X-ray spectra were fitted by a four-temperature apec model (with three components being the quiescent background), showing significant evolution of plasma temperature and emission measure over time. The estimated energy released in the LEIA band is ~3 * 10^39 erg, suggesting that this is likely the most energetic X-ray stellar flare with the longest duration detected to date.

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Xuan Mao, He-Yang Liu, Song Wang, Zhixing Ling, Weimin Yuan, Huaqing Cheng, Haiwu Pan, Dongyue Li, Fabio Favata, Tuo Ji, Jujia Zhang, Xinlin Zhao, Jing Wan, Zhiming Cai, Alberto J. Castro-Tirado, Yanfeng Dai, Licai Deng, Xu Ding, Kaifan Ji, Chichuan Jin, Yajuan Lei, Huali Li, Jun Lin, Huaqiu Liu, Mingjun Liu, Shuai Liu, Yuan Liu, Hui Sun, Shengli Sun, Xiaojin Sun, Jianrong Shi, Jianguo Wang, Jingxiu Wang, Wenxin Wang, Jianyan Wei, Liping Xin, Dingrong Xiong, Chen Zhang, Wenda Zhang, Yonghe Zhang, Xiaofeng Zhang, Donghua Zhao, Guiping Zhou. 2025-02-20. LEIA discovery of the longest-lasting and most energetic stellar X-ray flare ever detected. https://arxiv.org/abs/2410.17999

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