Detection of Flare-associated CME Candidates on Two M-dwarfs by GWAC and Fast, Time-resolved Spectroscopic Follow-ups

TL;DR

This study reports the detection of flare-associated CMEs on two M-dwarfs using high-cadence surveys and rapid spectroscopic follow-ups, revealing high velocities and significant masses that impact exoplanet habitability.

Contribution

First detection of flare-associated CMEs on M-dwarfs using combined high-cadence photometry and time-resolved spectroscopy, demonstrating the feasibility of such observations.

Findings

CME velocities of 500-700 km/s suggest high-energy stellar eruptions.

CME masses estimated between 1.5-4.5 x 10^19 g.

Flare energies in R-band up to 1.6 x 10^35 erg.

Abstract

The flare-associated stellar coronal mass ejection (CME) in solar-like and late type stars is quite essential for the habitability of an exoplanet. In this paper, we report detection of flare-associated CMEs in two M-dwarfs, thanks to the high cadence survey carried out by the Ground Wide-angle Camera system and the fast photometric and spectroscopic follow-ups. The flare energy in $R-$band is determined to be $1.6\times10^{35}\ \mathrm{erg}$ and $8.1\times10^{33}\ \mathrm{erg}$ based on the modeling of their light curves. The time-resolved spectroscopyic observations start at about 20 and 40 minutes after the trigger in both cases. The large projected maximum velocity of $\sim500-700\ \mathrm{km\ s^{-1}}$ suggests that the high velocity wing of their H$\alpha$ emission lines are most likely resulted from a CME event in both stars, after excluding the possibility of chromospheric evaporation and coronal rain. The masses of the CMEs are estimated to be $1.5-4.5\times10^{19}\ \mathrm{g}$ and $7.1\times10^{18}\ \mathrm{g}$.