Search

We describe advances on a method designed to derive accurate parameters of M dwarfs. Our analysis consists in comparing high-resolution infrared spectra acquired with the near-infrared spectro-polarimeter SPIRou to synthetic spectra computed from MARCS model atmospheres, in order to derive the effective temperature (T eff), surface gravity (log  g), metallicity (⁠|$\rm {[M/H]}$|⁠), and alpha-enhancement (⁠|$\rm {[\alpha /Fe]}$|⁠) of 44 M dwarfs monitored within the SPIRou Legacy Survey (SLS). Relying on 12 of these stars, we calibrated our method by refining our selection of well-modelled stellar lines, and adjusted the line list parameters to improve the fit when necessary. Our retrieved T eff, log  g , and |$\rm {[M/H]}$| are in good agreement with literature values, with dispersions of the order of 50 K in T eff and 0.1 dex in log  g and |$\rm {[M/H]}$|⁠. We report that fitting |$\rm {[\alpha /Fe]}$| has an impact on the derivation of the other stellar parameters, motivating us to extend our fitting procedure to this additional parameter. We find that our retrieved |$\rm {[\alpha /Fe]}$| are compatible with those expected from empirical relations derived in other studies. [ABSTRACT FROM AUTHOR]

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri star V410 Tau based on data collected mostly with SPIRou, the near-infrared (NIR) spectropolarimeter recently installed at the Canada-France-Hawaii Telescope , as part of the SPIRou Legacy Survey large programme, and with TESS between October and December 2019. Using Zeeman–Doppler Imaging (ZDI), we obtained the first maps of photospheric brightness and large-scale magnetic field at the surface of this young star derived from NIR spectropolarimetric data. For the first time, ZDI is also simultaneously applied to high-resolution spectropolarimetric data and very-high-precision photometry. V410 Tau hosts both dark and bright surface features and magnetic regions similar to those previously imaged with ZDI from optical data, except for the absence of a prominent dark polar spot. The brightness distribution is significantly less contrasted than its optical equivalent, as expected from the difference in wavelength. The large-scale magnetic field (⁠|${\sim}410$|  G), found to be mainly poloidal, features a dipole of |${\sim}390$|  G, again compatible with previous studies at optical wavelengths. NIR data yield a surface differential rotation slightly weaker than that estimated in the optical at previous epochs. Finally, we measured the radial velocity of the star and filtered out the stellar activity jitter using both ZDI and Gaussian Process Regression down to a precision of |${\sim}0.15$| and 0.08  |$\mathrm{km}\, \mathrm{s}^{-1}$| RMS, respectively, confirming the previously published upper limit on the mass of a potential close-in massive planet around V410 Tau. [ABSTRACT FROM AUTHOR]