An Extreme Stellar Prominence Eruption Observed by LAMOST Time-Domain Spectroscopy

TL;DR

This paper reports the first detection of an extreme stellar prominence eruption on an M dwarf star, observed via time-domain spectroscopy, revealing velocities exceeding escape speed and a massive prominence comparable to the star's mass.

Contribution

It presents the first detailed spectroscopic observation of an extreme stellar prominence eruption with velocities surpassing escape velocity, indicating a potential CME on an M dwarf star.

Findings

Eruptive prominence velocities exceed stellar escape velocity.

Largest equivalent width of blue-wing enhancement observed.

Prominence mass is among the largest reported for stellar eruptions.

Abstract

We report the detection of an extreme stellar prominence eruption on the M dwarf LAMOST J044431.62+235627.9, observed through time-domain H$\alpha$ spectroscopy with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). This prominence eruption was accompanied by a superflare lasting over 160.4 minutes. The H$\alpha$ line profile exhibits significant blue-wing enhancement during the impulsive phase and near the flare peak, with a projected bulk blueshift velocity of $-228\pm11$~km~s$^{-1}$ and a maximum blueshift velocity reaching $-605\pm15$~km~s$^{-1}$. Velocity analysis of the eruptive prominence at various heights above the stellar surface indicates that some of the projected ejection velocities along the line of sight exceed the corresponding escape velocities, suggesting a potential coronal mass ejection (CME). The equivalent width (EW) of the H$\alpha$ blue-wing enhancement in this eruption appears to be the largest observed to date and is comparable to the EW of the H$\alpha$ line profile during the quiescent phase of the host star. We performed a two-cloud modeling for the prominence and the associated flare, which suggests that the eruptive prominence has a mass ranging from $1.6 \times 10^{19}~\text{g}$ to $7.2 \times 10^{19}~\text{g}$. More importantly, the mass ratio of the erupting prominence to its host star is the largest among all reported stellar prominence eruptions/CMEs.