A giant magnetic eruption from the asymptotic giant branch star Mira A
Abstract
Mass loss during the advanced evolutionary stages of low- and intermediate-mass stars is traditionally attributed to dust-driven winds, whereas the influence of magnetic fields remains poorly constrained. However, recent observations show massive directional mass ejections from the nearby asymptotic giant branch (AGB) star Mira~A that appear not to be driven by radiation pressure on the dust. We observationally investigate whether magnetic fields are responsible for the mass loss ejections from Mira A. We obtained full-polarisation ALMA observations of the SiO v=1, J=5→4 maser transition at 215 GHz with angular resolutions of 1.5-2.6 au. The observations reveal a highly magnetized loop-like mass ejection traced by strongly polarised SiO masers extending to approximately eight stellar radii. The morphology, polarisation pattern, energetics, and kinematics indicate a magnetically driven eruption analogous to a stellar coronal mass ejection. The observations demonstrate that magnetic eruptions can dominate mass loss from evolved stars and imply that magnetic fields must become an integral component of future models of AGB, and potentially other cool giant, winds.
Related
- Periodic activity on the (sub)millimetre surface of the asymptotic giant branch star Mira A
- Infrared spectroscopy of the longest-period Galactic Mira variables from Palomar Gattini-IR: Identification of a candidate thermally pulsing Super-Asymptotic Giant Branch star
- Properties of Oxygen-rich Asymptotic Giant Branch stars in the LMC and the Milky Way
- CHASE Spectral Survey I: Measuring Contamination in the Color-selected J-region Asymptotic Giant Branch Distance Indicator
- Magnetic Eruption and Nucleosynthesis in GRνMHD Simulations of Spinning Neutron Star Mergers
BibTeX
@misc{vlemmings2026giant,
title = {{A giant magnetic eruption from the asymptotic giant branch star Mira A}},
author = {W. Vlemmings and M. Andriantsaralaza and B. Bojnordi Arbab and T. Khouri and B. Lankhaar and L. Planquart and E. De Beck and S. Del Palacio and E. Humphreys and D. Jadlovsky and M. Maercker and H. Olofsson and M. Saberi and M. Siebert and R. Unnikrishnan and S. Wedemeyer and M. Wittkowski},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2608.23695},
eprint = {2608.23695},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.23695},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A giant magnetic eruption from the asymptotic giant branch star Mira A
AU - W. Vlemmings
AU - M. Andriantsaralaza
AU - B. Bojnordi Arbab
AU - T. Khouri
AU - B. Lankhaar
AU - L. Planquart
AU - E. De Beck
AU - S. Del Palacio
AU - E. Humphreys
AU - D. Jadlovsky
AU - M. Maercker
AU - H. Olofsson
AU - M. Saberi
AU - M. Siebert
AU - R. Unnikrishnan
AU - S. Wedemeyer
AU - M. Wittkowski
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2608.23695
UR - https://arxiv.org/abs/2608.23695
AB - Mass loss during the advanced evolutionary stages of low- and intermediate-mass stars is traditionally attributed to dust-driven winds, whereas the influence of magnetic fields remains poorly constrained. However, recent observations show massive directional mass ejections from the nearby asymptotic giant branch (AGB) star Mira~A that appear not to be driven by radiation pressure on the dust. We observationally investigate whether magnetic fields are responsible for the mass loss ejections from Mira A. We obtained full-polarisation ALMA observations of the SiO v=1, J=5→4 maser transition at 215 GHz with angular resolutions of 1.5-2.6 au. The observations reveal a highly magnetized loop-like mass ejection traced by strongly polarised SiO masers extending to approximately eight stellar radii. The morphology, polarisation pattern, energetics, and kinematics indicate a magnetically driven eruption analogous to a stellar coronal mass ejection. The observations demonstrate that magnetic eruptions can dominate mass loss from evolved stars and imply that magnetic fields must become an integral component of future models of AGB, and potentially other cool giant, winds.
ER -