Small-Scale Magnetic Fields of Hyades M Dwarfs: Evolution with Age from the Pleiades to Field Stars
Abstract
Small-scale magnetic fields are derived for 18 M-dwarf stars in the Hyades open cluster through an analysis of Zeeman broadening in magnetically sensitive lines from the APOGEE spectra, resulting in mean magnetic fields ranging from 0.7 to 4.3 kG. Comparison with results for field stars hosting exoplanets and stars in the Pleiades open cluster from our previous works reveals distinct distributions of mean magnetic fields, reflecting differences in stellar age. Pleiades stars exhibit stronger fields (2965±632 G) and are predominantly in the saturated regime, while the roughly 500 million years older Hyades sample has weaker fields (1925±1028 G) with a larger dispersion, spanning both saturated and unsaturated regimes. Field stars show substantially weaker fields (573±272 G) and consistently occupy the unsaturated regime. Using the three samples, we derive the relationship between small-scale magnetic field strength and Rossby number, identifying saturation limits for the Rossby number (RoSAT=0.145) and mean magnetic field (⟨B⟩SAT=2452 G). Within the Hyades sample, we find that, at a given age, cooler stars tend to have stronger magnetic fields. This trend is less apparent in the other samples, due to the broader age distribution of the field stars and magnetic saturation among the Pleiades stars. Comparisons with isochrones indicate positive correlations between mean magnetic field strength and both stellar radius inflation and photospheric spot coverage. We also find positive correlations between magnetic field strength and chromospheric and coronal activity, with stronger fields associated with larger Hα equivalent width excess and higher X-ray-to-bolometric luminosity ratios.
Related
- TESS flares and chromospheric variability in the Pleiades, the Hyades, and Praesepe
- TESS flares and chromospheric variability in the Pleiades, the Hyades, and Praesepe
- Slowly Rotating M Dwarfs with Unusually Strong Magnetic Fields: Interpreting the Data in Terms of How Stars Acquire Fields and How They Lose Fields
- Transport of Magnetic Fields by Thermohaline Convection in Crystallizing White Dwarfs
- Protostellar evolution of intermediate-mass stars: Implications for the survival of fossil magnetic fields
BibTeX
@misc{wanderley2026smallscale,
title = {{Small-Scale Magnetic Fields of Hyades M Dwarfs: Evolution with Age from the Pleiades to Field Stars}},
author = {Fábio Wanderley and Katia Cunha and Oleg Kochukhov and Verne V. Smith and Diogo Souto and Lyra Cao and Kevin Covey and Simone Daflon and Steven R. Majewski and Marc Pinsonneault and Helio. J. Rocha-Pinto and Carlos. Allende Prieto},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.02919},
eprint = {2611.02919},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.02919},
}
RIS
TY - UNPB
TI - Small-Scale Magnetic Fields of Hyades M Dwarfs: Evolution with Age from the Pleiades to Field Stars
AU - Fábio Wanderley
AU - Katia Cunha
AU - Oleg Kochukhov
AU - Verne V. Smith
AU - Diogo Souto
AU - Lyra Cao
AU - Kevin Covey
AU - Simone Daflon
AU - Steven R. Majewski
AU - Marc Pinsonneault
AU - Helio. J. Rocha-Pinto
AU - Carlos. Allende Prieto
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.02919
UR - https://arxiv.org/abs/2611.02919
AB - Small-scale magnetic fields are derived for 18 M-dwarf stars in the Hyades open cluster through an analysis of Zeeman broadening in magnetically sensitive lines from the APOGEE spectra, resulting in mean magnetic fields ranging from 0.7 to 4.3 kG. Comparison with results for field stars hosting exoplanets and stars in the Pleiades open cluster from our previous works reveals distinct distributions of mean magnetic fields, reflecting differences in stellar age. Pleiades stars exhibit stronger fields (2965±632 G) and are predominantly in the saturated regime, while the roughly 500 million years older Hyades sample has weaker fields (1925±1028 G) with a larger dispersion, spanning both saturated and unsaturated regimes. Field stars show substantially weaker fields (573±272 G) and consistently occupy the unsaturated regime. Using the three samples, we derive the relationship between small-scale magnetic field strength and Rossby number, identifying saturation limits for the Rossby number (Ro_SAT=0.145) and mean magnetic field (⟨B⟩_SAT=2452 G). Within the Hyades sample, we find that, at a given age, cooler stars tend to have stronger magnetic fields. This trend is less apparent in the other samples, due to the broader age distribution of the field stars and magnetic saturation among the Pleiades stars. Comparisons with isochrones indicate positive correlations between mean magnetic field strength and both stellar radius inflation and photospheric spot coverage. We also find positive correlations between magnetic field strength and chromospheric and coronal activity, with stronger fields associated with larger Hα equivalent width excess and higher X-ray-to-bolometric luminosity ratios.
ER -