Correlations between laboratory line lists for FeH, CrH, and NiH and M-star spectra collected with ESPaDOnS and SPIRou

Abstract

Molecular bands of metal oxides and hydrides dominate the optical and near-infrared spectra of M dwarfs. High-resolution spectra of these bands have immense potential for determining many properties of these stars, such as effective temperature, surface gravity, elemental abundances, radial velocity, or surface magnetic fields. Techniques are being developed to do this but remain limited by the current availability and accuracy of molecular data and spectral line lists. This paper reports metal monohydride line lists selected from near-infrared and visible laboratory data to show that specific bands in several electronic transitions can be used to identify CrH, NiH, and FeH in M stars and to determine radial velocities from Doppler shifts. The possibility of measuring magnetic fields is also investigated for FeH and CrH. We used systematic cross-correlation analysis between unpolarised spectra from a selection of M stars and state-specific laboratory line lists. These lists were generated from a combination of existing data and new laboratory laser-excitation spectra recorded at Doppler-limited resolution, in zero-field conditions or in magnetic fields up to 0.6 tesla. Results. We show that transitions at visible wavelengths in FeH and NiH, usually neglected in the analysis of the spectra of M-type stars, do in fact contribute to the spectra, and we demonstrate the influence of magnetic sensitivity on selected transitions in CrH and FeH. Although the new line lists focus on transitions recorded at temperatures significantly lower than those of stellar objects, they remain pertinent because they cover some band-head regions of high spectral density. FeH bands can provide a useful supplement to atomic lines for the analysis of high-resolution optical and near-infrared spectra of M dwarfs. We demonstrate the influence of a magnetic field on CrH signatures around 862 nm.

Accepted for publication in A&A, 10 pages, 12 figures, 2 tables, additional material will be made available at CDS/Vizier

References in corpus (20)

• Large-scale magnetic topologies of late M dwarfs
• Large-scale magnetic topologies of early M dwarfs
• The First Direct Measurements of Magnetic Fields on Very Low-Mass Stars
• The 2020 release of the ExoMol database: molecular line lists for exoplanet and other hot atmospheres
• SPIRou: nIR velocimetry & spectropolarimetry at the CFHT
• Magnetic fields of M dwarfs
• Strong dipole magnetic fields in fast rotating fully convective stars
• Line-by-line velocity measurements, an outlier-resistant method for precision velocimetry
• Magnetic fields in M dwarfs from the CARMENES survey
• Investigating the young AU~Mic system with SPIRou: large-scale stellar magnetic field and close-in planet mass
• APERO: A PipelinE to Reduce Observations -- Demonstration with SPIRou
• Stellar Characterization of M-dwarfs from the APOGEE Survey: A Calibrator Sample for the M-dwarf Metallicities
• Constraining atmospheric parameters and surface magnetic fields with $\text{ZeeTurbo}$: an application to SPIRou spectra
• The SPIRou Legacy Survey Rotation period of quiet M dwarfs from circular polarization in near-infrared spectral lines: I. The SPIRou APERO analysis
• A high resolution spectral atlas of brown dwarfs
• Estimating the atmospheric properties of 44 M dwarfs from SPIRou spectra
• Predicted Landé $g$-factors for open shell diatomic molecules
• Evidence for chromium hydride in the atmosphere of Hot Jupiter WASP-31b
• The electronic bands of CrD, CrH, MgD and MgH: application to the "deuterium test"
• First spectropolarimetric measurement of a brown dwarf magnetic field in molecular bands