The ESO UVES/FEROS Large Programs of TESS OB pulsators

I. Global stellar parameters from high-resolution spectroscopy^★

¹ Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
e-mail: nadya.serebriakova@kuleuven.be
² Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
³ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
⁴ Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands

Received: 8 February 2023
Accepted: 16 May 2023

Abstract

Context. Modern stellar structure and evolution theory suffers from a lack of observational calibration for the interior physics of intermediate- and high-mass stars. This leads to discrepancies between theoretical predictions and observed phenomena that are mostly related to angular momentum and element transport. Analyses of large samples of massive stars connecting state-of-the-art spectroscopy to asteroseismology may provide clues as to how to improve our understanding of their interior structure.

Aims. We aim to deliver a sample of O- and B-type stars at metallicity regimes of the Milky Way and the Large Magellanic Cloud (LMC) galaxies with accurate atmospheric parameters from high-resolution spectroscopy, along with a detailed investigation of line-profile broadening, both for the benefit of future asteroseismic studies.

Methods. After describing the general aims of our two Large Programs, we develop a dedicated methodology to fit spectral lines and deduce accurate global stellar parameters from high-resolution multi-epoch UVES and FEROS spectroscopy. We use the best available atmosphere models for three regimes covered by our global sample, given its breadth in terms of mass, effective temperature, and evolutionary stage.

Results. Aside from accurate atmospheric parameters and locations in the Hertzsprung-Russell diagram, we deliver detailed analyses of macroturbulent line broadening, including estimations of the radial and tangential components. We find that these two components are difficult to disentangle from spectra with signal-to-noise ratios of below 250.

Conclusions. Future asteroseismic modelling of the deep interior physics of the most promising stars in our sample will provide much needed information regarding OB stars, including those of low metallicity in the LMC.