Magnetic Fields in M-dwarf Members of the Pleiades Open Cluster Using APOGEE Spectra

• Published in: The Astrophysical journal 2024-08, Vol.971 (1), p.112
• Main Authors: Wanderley, Fábio, Cunha, Katia, Kochukhov, Oleg, Smith, Verne V., Souto, Diogo, Cao, Lyra, Covey, Kevin, Majewski, Steven R., Martinez, Cintia, Muirhead, Philip S., Pinsonneault, Marc, Allende Prieto, C., Stassun, Keivan G.
• Format: Article
• Language: English
• Subjects: Apogees; Astronomical models; Atmospheric models; Clusters; Coronal activity; Correlation; Emission lines; Field strength; H alpha line; Line spectra; Luminosity; M dwarf stars; Magnetic fields; Markov chains; Monte Carlo simulation; Near infrared astronomy; Open star clusters; Radiative transfer; Red dwarf stars; Rossby number; Sky surveys (astronomy); Spectra; Stars; Stellar activity; Stellar atmospheres; Stellar coronas; Stellar magnetic fields; Stellar models; Stellar rotation
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/ad571f

Average magnetic field measurements are presented for 62 M-dwarf members of the Pleiades open cluster, derived from Zeeman-enhanced Fe i lines in the H band. A Markov Chain Monte Carlo methodology was employed to model magnetic filling factors using Sloan Digital Sky Survey (SDSS) IV APOGEE high-resolution spectra, along with the radiative transfer code Synmast, MARCS stellar atmosphere models, and the APOGEE Data Release 17 spectral line list. There is a positive correlation between mean magnetic fields and stellar rotation, with slow-rotator stars (Rossby number, Ro > 0.13) exhibiting a steeper slope than rapid rotators (Ro < 0.13). However, the latter sample still shows a positive trend between Ro and magnetic fields, which is given by 〈 B 〉 = 1604 × Ro −0.20 . The derived stellar radii when compared with physical isochrones show that, on average, our sample shows radius inflation, with median enhanced radii ranging from +3.0% to +7.0%, depending on the model. There is a positive correlation between magnetic field strength and radius inflation, as well as with stellar spot coverage, correlations which together indicate that stellar spot-filling factors generated by strong magnetic fields might be the mechanism that drives radius inflation in these stars. We also compare our derived magnetic fields with chromospheric emission lines (H α , H β , and Ca ii K), as well as with X-ray and H α to bolometric luminosity ratios, and find that stars with higher chromospheric and coronal activity tend to be more magnetic.