- The magnetic field in the photospheric and circumstellar components of Herbig Ae stars
- Astronomy & Astrophysics
- Pages (from-to)
- Document type
- Faculty of Science (FNWI)
- Anton Pannekoek Institute for Astronomy (API)
Aims.We investigate the photospheric and circumstellar (CS) magnetic field components separately in seven Herbig Ae stars. Methods: The study is based on low-resolution (RËœ 2000 and 4000) spectropolarimetric data collected from 2003 to 2005 at the Very Large Telescope (ESO, Chile) with the multi-mode instrument FORS1. Results: We show that the spectropolarimetric results strongly depend on the level of CS contribution to the stellar spectra. We have improved the determination accuracy of magnetic fields up to the 7sigma level in the two Herbig Ae stars HD 139614 and HD 144432, observed in 2005 when these objects were at a low level state in their CS activity. We have established that at a higher level state of CS activity the polarisation signatures are mainly related to the CS matter. The presence of CS polarisation signatures formed in the stellar wind supports the assumption that the magnetic centrifuge is one of the main mechanisms of wind acceleration. Conclusions: .We conclude that the most effective way to investigate the magnetism of Herbig Ae stars is to monitor their spectropolarimetric behaviour at different stages of CS activity. Obviously, higher-resolution spectropolarimetric observations would extend the sample of spectral lines which can be used to measure magnetic fields at different levels in the stellar atmosphere and CS envelope. These observations will give a more complete insight into the magnetic topology in Herbig Ae stars. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO programme Nos. 072.D-0377, 073.D-0464, 074.C-0463, and 075.D-0507).
- go to publisher's site
- DOI: 10.1051/0004-6361:20066090; eprintid: arXiv:astro-ph/0610439
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library, or send a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.