Magnetic fields in M dwarfs from the CARMENES survey

Abstract

M dwarfs are known to generate the strongest magnetic fields among main-sequence stars with convective envelopes, but the link between the magnetic fields and underlying dynamo mechanisms, rotation, and activity still lacks a consistent picture. In this work we measure magnetic fields from the high-resolution near-infrared spectra taken with the CARMENES radial-velocity planet survey in a sample of 29 active M dwarfs and compare our results against stellar parameters. We use the state-of-the-art radiative transfer code to measure total magnetic flux densities from the Zeeman broadening of spectral lines and filling factors. We detect strong kG magnetic fields in all our targets. In 16 stars the magnetic fields were measured for the first time. Our measurements are consistent with the magnetic field saturation in stars with rotation periods P<4d. The analysis of the magnetic filling factors reveal two different patterns of either very smooth distribution or a more patchy one, which can be connected to the dynamo state of the stars and/or stellar mass. Our measurements extend the list of M dwarfs with strong surface magnetic fields. They also allow us to better constrain the interplay between the magnetic energy, stellar rotation, and underlying dynamo action. The high spectral resolution and observations at near-infrared wavelengths are the beneficial capabilities of the CARMENES instrument that allow us to address important questions about the stellar magnetism.

13 pages of main text, 14 pages of online material, 2 tables

References in corpus (18)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Dartmouth Stellar Evolution Database
• Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
• Molecfit: A general tool for telluric absorption correction II. Quantitative evaluation on ESO-VLT X-Shooter spectra
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• Large-scale magnetic topologies of late M dwarfs
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• The First Direct Measurements of Magnetic Fields on Very Low-Mass Stars
• Generalized investigation of the rotation-activity relation: Favouring rotation period instead of Rossby number
• CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS
• Strong dipole magnetic fields in fast rotating fully convective stars
• On the environment surrounding close-in exoplanets
• The Threatening Environment of the TRAPPIST-1 Planets
• The global and small-scale magnetic fields of fully convective, rapidly spinning M dwarf pair GJ65A and B
• Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating
• Magnetic cycles in a dynamo simulation of fully convective M-star Proxima Centauri
• Surprisingly different starspot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB
• Magnetic Field of the Eclipsing M Dwarf Binary YY Gem

Cited by in corpus (26)

• Magnetic fields of M dwarfs
• The evolution of the solar wind
• The CARMENES search for exoplanets around M dwarfs. Guaranteed time observations Data Release 1 (2016-2020)
• Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic
• From Starspots to Stellar Coronal Mass Ejections -- Revisiting Empirical Stellar Relations
• Low-frequency monitoring of flare star binary CR Draconis: Long-term electron-cyclotron maser emission
• The CARMENES search for exoplanets around M dwarfs: Convective shift and starspot constraints from chromatic radial velocities
• Tuning the Exo-Space Weather Radio for Stellar Coronal Mass Ejections
• Multi-instrumental view of magnetic fields and activity of $\epsilon$ Eridani with SPIRou, NARVAL, and TESS
• The Earth-like Galactic cosmic ray intensity in the habitable zone of the M dwarf GJ 436
• Rotational modulation of spectroscopic Zeeman signatures in low-mass stars
• MHD study of extreme space weather conditions for exoplanets with Earth-like magnetospheres: On habitability conditions and radio-emission
• Coronal X-Ray Emission from Nearby, Low-Mass, Exoplanet Host Stars Observed by the MUSCLES and Mega-MUSCLES HST Treasury Survey Projects
• Eclipse Mapping of EXO 0748-676: Evidence for a Massive Neutron Star
• Magnetic Fields of M Dwarfs from the Pleiades Open Cluster
• The CARMENES search for exoplanets around M dwarfs. Line-by-line sensitivity to activity in M dwarfs
• Magnetic Inflation and Stellar Mass. V. Intensification and saturation of M dwarf absorption lines with Rossby number
• Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4
• Magnetic interactions in orbital dynamics
• The impact of unresolved magnetic spots on high precision radial velocity measurements
• Correlations between laboratory line lists for FeH, CrH, and NiH and M-star spectra collected with ESPaDOnS and SPIRou
• Contemporaneous Observations of $H\alpha$ Luminosities and Photometric Amplitudes for M Dwarfs
• The CARMENES search for exoplanets around M dwarfs. The impact of rotation and magnetic fields on the radial velocity jitter in cool stars
• Chromaticity of stellar activity in radial velocities : Anti-correlated families of lines on the M dwarf EV Lac with SPIRou and SOPHIE
• Searching for star-planet interactions in GJ 486 at radio wavelengths with the uGMRT
• Radio Emission from UV Cet: Auroral Emission from a Stellar Magnetosphere