The Magnetic Early B-type Stars II: stellar atmospheric parameters in the era of Gaia. (arXiv:1902.02713v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Shultz_M/0/1/0/all/0/1">M. E. Shultz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wade_G/0/1/0/all/0/1">G. A. Wade</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rivinius_T/0/1/0/all/0/1">Th. Rivinius</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alecian_E/0/1/0/all/0/1">E. Alecian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Neiner_C/0/1/0/all/0/1">C. Neiner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Petit_V/0/1/0/all/0/1">V. Petit</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wisniewski_J/0/1/0/all/0/1">J. P. Wisniewski</a>, the <a href="http://arxiv.org/find/astro-ph/1/au:+MiMeS/0/1/0/all/0/1">MiMeS</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Collaboration_BinaMIcS/0/1/0/all/0/1">BinaMIcS Collaborations</a>
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.
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.
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