Magnetic fields in M dwarfs from the CARMENES survey

Abstract

Context. 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. Aims. In this work we measure magnetic fields from the high-resolution near-infrared spectra taken with the CARMENES radialvelocity planet survey in a sample of 29 active M dwarfs and compare our results against stellar parameters. Methods. 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. Results. 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 < 4 d. 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. Conclusions. 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.

The impact of unresolved magnetic spots on high-precision radial velocity measurements

“…In the future we will apply this approach to other stars with a range of spectral types. For instance, the unresolved magnetic field can be measured with an indication of its complexity using methods such as those developed by (Shulyak et al 2019 |P fit P p |/P p Figure 3. Planet detection simulations that show a mass and period fit errors for grids of simulated planets for each of the spot distribution cases (section 2.2) and observational strategies.…”

Early science with SPIRou: near-infrared radial velocity and spectropolarimetry of the planet-hosting star HD 189733

“…This value of the magnetic field strength and flux for HD 189733 is intermediate between nonactive, slow-rotators M dwarfs such as Gl 411 or Gl 380, which have typical fields lower than 1 kG (Moutou et al 2017;Flores et al 2019), and fast-rotator M dwarfs whose field usually ranges from 2 to 5 kG (Shulyak et al 2019). With a rotational period of 12 days, HD 189733 is similar to Gl 49, DS Leo, Gl 208 or CE Boo, whose magnetic field fluxes lie between 0.5 and 2 kG according to far-red measurements of FeH and Ti (see Fig.…”

Usage of information technologies for increasing quality of transport operations

“…In the case of different configurations of the roadway, we can accept that the boundaries (1) of a system functionality scope in the general case are random variables with some common probability density ωt (α, β) [8][9][10]. Then, for all possible values of the functionality scope limits, the realization probability of target goal of the transport unit steerability (mathematical expectation of the solution of the assigned task) by steering control is written in the form:…”