2004/08/31 by S. Hubrig, C. M. Zhang, P. North +6 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1002/asna.200710773
published as Astron.Nachr.328:475-482,2007 · 16 pages, 22 figures, 5 tables, accepted for publication in AN
arxiv created 2007/04/11 · openalex publication_date 2007/06/19 · arxiv updated 2015/05/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We re-discuss the evolutionary state of upper main sequence magnetic stars using a sample of Ap and Bp stars with accurate Hipparcos parallaxes and definitely determined longitudinal magnetic fields. We confirm our previous results obtained from the study of Ap and Bp stars with accurate measurements of the mean magnetic field modulus and mean quadratic magnetic fields that magnetic stars of mass M < 3 Msun are concentrated towards the centre of the main-sequence band. In contrast, stars with masses M > 3 Msun seem to be concentrated closer to the ZAMS. The study of a few known members of nearby open clusters with accurate Hipparcos parallaxes confirms these conclusions. Stronger magnetic fields tend to be found in hotter, younger and more massive stars, as well as in stars with shorter rotation periods. No evidence is found for any loss of angular momentum during the main-sequence life. The magnetic flux remains constant over the stellar life time on the main sequence. An excess of stars with large obliquities beta is detected in both higher and lower mass stars. The obliquity angle distribution as inferred from the distribution of r-values appears random at the time magnetic stars become observable on the H-R diagram. After quite a short time spent on the main sequence, the obliquity angle beta tends to reach values close to either 90 deg or 0 deg for M < 3 Msun. The evolution of the obliquity angle beta seems to be somewhat different for low and high mass stars. While we find a strong hint for an increase of beta with the elapsed time on the main sequence for stars with M > 3 Msun, no similar trend is found for stars with M < 3 Msun. However, the predominance of high values of beta at advanced ages in these stars is notable.