Space Weather & Heliophysics

Magnetic Fields in a Sample of Planet-hosting M Dwarf Stars from Kepler, K2, and TESS Observed by APOGEE

By Keith Cowing
Status Report
astro-ph.SR
September 11, 2024
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Magnetic Fields in a Sample of Planet-hosting M Dwarf Stars from Kepler, K2, and TESS Observed by APOGEE
Magnetic field analysis for the star 2M07590587+1523294. The left panels show the four Fe I lines used in the modeling: black dots are the observed APOGEE spectrum, red dashed lines are synthetic profiles computed without a magnetic field, and dark blue lines are our best fits obtained from the MCMC modeling. The right panel is a corner plot that presents the median and uncertainties (from 16th and 84th percentiles) of the derived parameters, which includes filling factors from magnetic fields between 2 and 6 kG in steps of 2 kG. We also show the final magnetic field result and its uncertainties. — astro-ph.SR

Stellar magnetic fields have a major impact on space weather around exoplanets orbiting low-mass stars. From an analysis of Zeeman-broadened Fe I lines measured in near-infrared SDSS/APOGEE spectra, mean magnetic fields are determined for a sample of 29 M dwarf stars that host closely orbiting small exoplanets.

The calculations employed the radiative transfer code Synmast and MARCS stellar model atmospheres. The sample M dwarfs are found to have measurable mean magnetic fields ranging between ∼0.2 to ∼1.5 kG, falling in the unsaturated regime on the vs Prot plane. The sample systems contain 43 exoplanets, which include 23 from Kepler, nine from K2, and nine from TESS.

We evaluated their equilibrium temperatures, insolation, and stellar habitable zones and found that only Kepler-186f and TOI-700d are inside the habitable zones of their stars. Using the derived values of for the stars Kepler-186 and TOI-700 we evaluated the minimum planetary magnetic field that would be necessary to shield the exoplanets Kepler-186f and TOI-700d from their host star’s winds, considering reference magnetospheres with sizes equal to those of the present-day and young Earth, respectively.

Assuming a ratio of 5% between large-to-small scale B-fields, and a young-Earth magnetosphere, Kepler-186f and TOI-700d would need minimum planetary magnetic fields of, respectively, 0.05 and 0.24 G. These values are considerably smaller than Earth’s magnetic field of 0.25 G≲B≲0.65 G, which suggests that these two exoplanets might have magnetic fields sufficiently strong to protect their atmospheres and surfaces from stellar magnetic fields.

Fábio Wanderley, Katia Cunha, Verne Smith, Oleg Kochukhov, Diogo Souto, Carlos Allende Prieto, Suvrath Mahadevan, Steven Majewski, Philip Muirhead, Marc Pinsonneault, Ryan Terrien

Comments: Accepted for publication by The Astrophysical Journal (ApJ)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2409.06637 [astro-ph.SR] (or arXiv:2409.06637v1 [astro-ph.SR] for this version)
https://doi.org/10.48550/arXiv.2409.06637
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Submission history
From: Fábio Carneiro Wanderley
[v1] Tue, 10 Sep 2024 16:47:59 UTC (391 KB)
https://arxiv.org/abs/2409.06637
Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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