The surface nitrogen abundance of a massive star in relation to its oscillations, rotation, and magnetic field

Conny Aerts, Geert Molenberghs, Michael G. Kenward, Coralie Neiner

Institute of Astronomy, KULeuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium;
Department of Astrophysics, IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands;
Faculty of Science, Hasselt University, Martelarenlaan 42,
B-3500 Hasselt, Belgium;
I-BioStat, KULeuven, Kapucijnenvoer 35,
B-3000 Leuven, Belgium;
Department of Medical Statistics, London School of Hygiene and
Tropical Medicine, Keppel Street,
London WC1E7HT, United Kingdom;
LESIA, UMR 8109 du CNRS, Observatoire de Paris, UPMC, Paris
Diderot, 5 Place Jules Janssen 92195 Meudon Cedex, France

We have composed a sample of 68 massive stars in our galaxy whose projected
rotational velocity, effective temperature and gravity are available from
high-precision spectroscopic measurements. The additional seven observed
variables considered here are their surface nitrogen abundance, rotational
frequency, magnetic field strength, and the amplitude and frequency of their
dominant acoustic and gravity mode of oscillation. Multiple linear regression
to estimate the nitrogen abundance combined with principal components analysis,
after addressing the incomplete and truncated nature of the data, reveals that
the effective temperature and the frequency of the dominant acoustic oscillation
mode are the only two significant predictors for the nitrogen abundance,
while the projected rotational velocity and the rotational frequency have no
predictive power. The dominant gravity mode and the magnetic field strength
are correlated with the effective temperature but have no predictive power for
the nitrogen abundance.
Our findings are completely based on observations and their proper
statistical treatment and call for a new strategy in evaluating the
outcome of stellar evolution computations.

Reference: Accepted for publication in The Astrophysical Journal
Status: Manuscript has been accepted


Comments: Table 3 in electronic format available upon request.