Zeeman Doppler Imaging of $tau$Ceti: The Weakest Magnetic Field Detected in a Sun-like Star
Federica Chiti, Oleg Kochukhov, Jennifer L. van Saders, Travis S. Metcalfe
arXiv:2509.12310v1 Announce Type: new
Abstract: For nearly a decade, observations have shown that many older Sun-like stars spin faster than predicted, a phenomenon known as weakened magnetic braking (WMB). The leading hypothesis for WMB is a weakening of the large-scale dipole field, which leads to a less efficient angular momentum loss. To test this hypothesis on a star known to be in the WMB regime, we present the first Zeeman Doppler Imaging (ZDI) map of the Sun-like star $tau$Ceti, reconstructed using spectropolarimetric data from the Canada-France-Hawai’i Telescope (CFHT). Our ZDI analysis reveals a remarkably simple, stable and weak ($langle Brangle =0.17 mathrm{G}$) magnetic field, characterized by a predominantly dipolar ($sim92%$ magnetic energy contained in $l=1$ modes), and highly axisymmetric ($sim88%$ magnetic energy contained in $m
Abstract: For nearly a decade, observations have shown that many older Sun-like stars spin faster than predicted, a phenomenon known as weakened magnetic braking (WMB). The leading hypothesis for WMB is a weakening of the large-scale dipole field, which leads to a less efficient angular momentum loss. To test this hypothesis on a star known to be in the WMB regime, we present the first Zeeman Doppler Imaging (ZDI) map of the Sun-like star $tau$Ceti, reconstructed using spectropolarimetric data from the Canada-France-Hawai’i Telescope (CFHT). Our ZDI analysis reveals a remarkably simple, stable and weak ($langle Brangle =0.17 mathrm{G}$) magnetic field, characterized by a predominantly dipolar ($sim92%$ magnetic energy contained in $l=1$ modes), and highly axisymmetric ($sim88%$ magnetic energy contained in $m
2025-09-17
