Although flares from late-type main-sequence stars have been frequently detected in multi-wavelength, the associated dynamical process has been rarely reported so far. Here, we report follow-up observations of an X-ray transient triggered by WXT onboard the Einstein Probe at UT08:45:08 in 2024, May 7. The photometry in multi-bands and time-resolved spectroscopy started at 3 and 7.5 hours after the trigger, respectively, which enables us to identify the transient as a flare of the M-dwarf 2MASS J12184187-0609123. The bolometric energy released in the flare is estimated to be ∼1036erg from its X-ray light curve. The Hα emission-line profile obtained at about 7 hours after the trigger shows an evident blue asymmetry with a maximum velocity of 200−250kms−1. The blue wing can be likely explained by the chromospheric temperature (cool) upflow associated with chromospheric evaporation, in which the mass of the evaporating plasma is estimated to be 1.2×1018g. In addition, a prominence eruption with an estimated mass of 7×1015g<Mp<7×1018g can not be entirely excluded.
@article{arxiv.2410.03114,
title = {Potential Chromospheric Evaporation in A M-dwarf's Flare Triggered by Einstein Probe Mission},
author = {J. Wang and X. Mao and C. Gao and H. Y. Liu and H. L. Li and H. W. Pan and C. Wu and Y. Liu and G. W. Li and L. P. Xin and S. Jin and D. W. Xu and E. W. Liang and W. M. Yuan and J. Y. Wei},
journal= {arXiv preprint arXiv:2410.03114},
year = {2024}
}