Fallback-triggered Reconnection Drives Coronal Mass Ejections on II Pegasi
- 1Chinese Academy of Sciences
Abstract
Stellar coronal mass ejections (CMEs) play key roles in stellar evolution and planetary habitability. On the Sun, CMEs typically originate from preexisting prominences or filaments, while materials condensed via the evaporation–condensation process have only been observed to remain confined or fall back as rain—never to trigger reconnection or drive eruptions. Here, we present high-resolution spectroscopic observations of II Pegasi (II Peg) obtained by the NARVAL, which captured successive sequences of loop-top condensation, gravitational fallback, and subsequent ejection, associated with stellar flares. Three successive flares originating from the same active region exhibited similar early phase spectral evolution but diverged into distinct final outcomes. Two flares developed to show blueshifted emission in the H α line, with maximum velocities reaching 1.7 and 1.07 times the stellar surface escape velocity (∼306 km s ⁻¹ ), indicating mass ejections. In contrast, the third flare exhibited a redshifted emission feature in the H α line, signifying a confined event. We interpret these contrasting behaviors within an impact-triggered magnetic reconnection framework, in which the final trajectory—eruptive or confined—is set by whether the newly reconnected field lines open outward or remain closed. Our studies show that stellar CMEs can arise directly from coronal condensations that fall back, trigger reconnection, and are subsequently ejected, revealing a previously unrecognized eruption pathway.
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BibTeX
@article{cao2026fallbacktriggered,
title = {{Fallback-triggered Reconnection Drives Coronal Mass Ejections on II Pegasi}},
author = {Dongtao Cao and Shenghong Gu},
journal = {The Astrophysical Journal Letters},
year = {2026},
month = oct,
doi = {10.3847/2041-8213/aeb005},
url = {https://iopscience.iop.org/article/10.3847/2041-8213/aeb005},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Fallback-triggered Reconnection Drives Coronal Mass Ejections on II Pegasi
AU - Dongtao Cao
AU - Shenghong Gu
PY - 2026
DA - 2026/10/22
JO - The Astrophysical Journal Letters
DO - 10.3847/2041-8213/aeb005
UR - https://iopscience.iop.org/article/10.3847/2041-8213/aeb005
AB - Stellar coronal mass ejections (CMEs) play key roles in stellar evolution and planetary habitability. On the Sun, CMEs typically originate from preexisting prominences or filaments, while materials condensed via the evaporation–condensation process have only been observed to remain confined or fall back as rain—never to trigger reconnection or drive eruptions. Here, we present high-resolution spectroscopic observations of II Pegasi (II Peg) obtained by the NARVAL, which captured successive sequences of loop-top condensation, gravitational fallback, and subsequent ejection, associated with stellar flares. Three successive flares originating from the same active region exhibited similar early phase spectral evolution but diverged into distinct final outcomes. Two flares developed to show blueshifted emission in the H α line, with maximum velocities reaching 1.7 and 1.07 times the stellar surface escape velocity (∼306 km s ⁻¹ ), indicating mass ejections. In contrast, the third flare exhibited a redshifted emission feature in the H α line, signifying a confined event. We interpret these contrasting behaviors within an impact-triggered magnetic reconnection framework, in which the final trajectory—eruptive or confined—is set by whether the newly reconnected field lines open outward or remain closed. Our studies show that stellar CMEs can arise directly from coronal condensations that fall back, trigger reconnection, and are subsequently ejected, revealing a previously unrecognized eruption pathway.
SN - 2041-8205
SN - 2041-8213
ER -