Paper

Multi-wavelength Study of A Superflare on RS CVn-type Star HD22468 Triggered at Hard X-ray by SVOM

Godet, O, S Le Stum, Li, H L, Cavet, C, Jin, J J, Wang, X G, Zheng, J, Li, G W, Rodriguez, J, Wang, J, Dai, Z G, Bouchet, L, Liang, E W, Jiang, N, Wang, X Y, Zhang, S N, Yang, H, Guillot, S, Qiu, Y L, C Wu, Mao, X, Goldwurm, A, Y Xu, Schanne, S, Xin, L P, Wei, J Y, Bacon, P, Xie, W J, Coleiro, A, Lu, X M, Han, X H, Tao, L, Cai, H B, Huang, M H, Zhang, L, Huang, L, Cangemi, F, Cordier, B, Bellemont, N

2026

Overview

Detection of stellar flares at hard X-ray is still rare at the current stage. A transient was recently detected by the hard X-ray camera, ECLAIRs onboard the SVOM mission at 11:39:01.2UT on 2025, January 09. Simultaneous monitor in the optical band on the ground by SVOM/GWAC and follow-up spectroscopy enable us to confirm that the transient is caused by a superflare on HD~22468, a RS CVn-type star. The bolometric energy released in the flare is estimated to be \\(\\sim7.2\\times10^{37}-1.7\\times10^{38}\\ \\mathrm{erg}\\). The hard X-ray spectra of the event at the peak can be reproduced by the ``apec'' model of a hot plasma with a temperature of \\(106^{+27}_{-22}\\)~MK. In the optical range, the H\\(\\alpha\\) emission-line profile obtained at \\(\\sim1.7\\) hrs after the trigger shows a bulk blueshift of \\(-96\\pm20\\ \\mathrm{km\\ s^{-1}}\\), which can be explained by either a chromospheric evaporation or a prominence eruption. The ejected mass is estimated to be \\(3.9\\times10^{20}\\) g for the evaporating plasma, and to be \\(3.2\\times10^{21}\\ \\mathrm{g}

• Publisher: Cornell University Library, arXiv.org
• Subject: Blue shift / Prominences / Spectrum analysis / Stellar flares / X ray spectra