# The Magnetic Early B-type Stars II: stellar atmospheric parameters in the era of Gaia

## TL;DR

This study measures atmospheric parameters of magnetic early B-type stars using high-resolution spectra and Gaia data, revealing revised surface gravities, luminosities, and insights into stellar rotation and magnetic braking.

## Contribution

It provides new measurements of effective temperatures and surface gravities for magnetic B-type stars, improving parameter accuracy and analyzing their relation to rotation and magnetic properties.

## Key findings

- Good agreement of $T_{eff}$ with previous studies
- Revised surface gravities, especially photometrically derived ones
- Luminosities generally lower than previous reports

## Abstract

Atmospheric parameters determined via spectral modelling are unavailable for many of the known magnetic early B-type stars. We utilized high-resolution spectra together with NLTE models to measure effective temperatures $T_{\rm eff}$ and surface gravities $\log{g}$ of stars for which these measurements are not yet available. We find good agreement between our $T_{\rm eff}$ measurements and previous results obtained both photometrically and spectroscopically. For $\log{g}$, our results are compatible with previous spectroscopic measurements; however, surface gravities of stars previously determined photometrically have been substantially revised. We furthermore find that $\log{g}$ measurements obtained with HARPSpol are typically about 0.1 dex lower than those from comparable instruments. Luminosities were determined using Gaia Data Release 2 parallaxes. We find Gaia parallaxes to be unreliable for bright stars ($V<6$ mag) and for binaries; in these cases we reverted to Hipparcos parallaxes. In general we find luminosities systematically lower than those previously reported. Comparison of $\log{g}$ and $\log{L}$ to available rotational and magnetic measurements shows no correlation between either parameter with magnetic data, but a clear slow-down in rotation with both decreasing $\log{g}$ and increasing $\log{L}$, a result compatible with the expectation that magnetic braking should lead to rapid magnetic spindown that accelerates with increasing mass-loss.