Spectropolarimetric Constraints on the Maunder Minimum Analog HD 166620: Evidence for Weakened Magnetic Braking
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arXiv
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| Auteurs principaux: | , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866915873622589440 |
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| author | Chiti, Federica van Saders, Jennifer L. Kochukhov, Oleg Metcalfe, Travis S. |
| author_facet | Chiti, Federica van Saders, Jennifer L. Kochukhov, Oleg Metcalfe, Travis S. |
| contents | We present the first spectropolarimetric time-series analysis of the Maunder Minimum analog HD 166620, using 12 nights of data from CFHT/SPIRou and a single epoch from CFHT/ESPaDOnS. While individual Stokes $V$ profiles exhibit no significant polarization signatures, we leverage the rotational coverage of the SPIRou dataset to compute a grand average LSD profile. Forward modeling of the cumulative Stokes $V$ signal, assuming a purely axisymmetric dipole, yields a best-fit dipole field strength of $B_{\rm dip} = 1.10^{+0.95}_{-0.90}$G ($3σ$). This field strength matches simulations of the solar dipole during the Maunder Minimum phase. Our results are consistent with independent constraints on the dipole field strength from an LBT/PEPSI snapshot and exclude the presence of strong non-axisymmetric fields potentially missed by this single-epoch observation. These findings provide direct empirical evidence that the transition to weakened magnetic braking involves a weakening of the large-scale magnetic field and suggest that HD 166620 represents a state comparable to the Sun near the peak activity of a grand minimum. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_18139 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Spectropolarimetric Constraints on the Maunder Minimum Analog HD 166620: Evidence for Weakened Magnetic Braking Chiti, Federica van Saders, Jennifer L. Kochukhov, Oleg Metcalfe, Travis S. Solar and Stellar Astrophysics We present the first spectropolarimetric time-series analysis of the Maunder Minimum analog HD 166620, using 12 nights of data from CFHT/SPIRou and a single epoch from CFHT/ESPaDOnS. While individual Stokes $V$ profiles exhibit no significant polarization signatures, we leverage the rotational coverage of the SPIRou dataset to compute a grand average LSD profile. Forward modeling of the cumulative Stokes $V$ signal, assuming a purely axisymmetric dipole, yields a best-fit dipole field strength of $B_{\rm dip} = 1.10^{+0.95}_{-0.90}$G ($3σ$). This field strength matches simulations of the solar dipole during the Maunder Minimum phase. Our results are consistent with independent constraints on the dipole field strength from an LBT/PEPSI snapshot and exclude the presence of strong non-axisymmetric fields potentially missed by this single-epoch observation. These findings provide direct empirical evidence that the transition to weakened magnetic braking involves a weakening of the large-scale magnetic field and suggest that HD 166620 represents a state comparable to the Sun near the peak activity of a grand minimum. |
| title | Spectropolarimetric Constraints on the Maunder Minimum Analog HD 166620: Evidence for Weakened Magnetic Braking |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2603.18139 |